Describes human eye optics.
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Aberration and Ophthalmic Lens Design.pptJayendra Jha
This document discusses various types of optical aberrations that occur when light passes through lenses and the human eye, including chromatic aberration, spherical aberration, oblique astigmatism, coma, and image distortion. It explains how each aberration leads to imperfect image formation and describes techniques used to reduce their effects, such as using multiple lens elements made of different materials, aspheric surfaces, and the optical properties of the eye itself. The document also provides examples of tests like the duochrome test that evaluate these aberrations during eye exams.
Bifocals are lenses with two optical powers, one for distance and one for near. There are several types of bifocal segments including round, flat top, curve top, ribbon, and Franklin style. Bifocals can be made through fused, one piece, or cemented constructions. When measuring for bifocals, the frame is positioned as it will be worn and the bifocal height is measured from the lower limbus or lid margin using a vertical ruler. This ensures the bifocal segment will be at the proper height for the wearer.
The document discusses key optical concepts including aperture stops, pupils, field of view, and depth of field. It defines an aperture stop as the limiting diameter that determines the amount of light reaching the imaging area. An entrance pupil is the image of the aperture stop from the object plane, while an exit pupil is the image from the image plane. A field stop limits the size of the object that can be imaged, and vignetting occurs when rays do not pass through the entire optical system. The depth of field refers to the zone in front of and behind the focal point that appears sharp in an image.
The document discusses the history and process of manufacturing glass and lenses. It provides details on:
1) Glassmaking has been traced back to 3500 BC based on the oldest glass beads, though its discovery is unknown. Glass was initially used for jewelry before being made into art objects in 16th century BC.
2) When heated to high temperatures, sand melts and becomes glass through a molecular structure change.
3) Lens manufacturing involves measuring a patient's prescription, selecting frames, grinding lenses to the correct optical power, and fitting lenses into frames through processes like cutting, edging and mounting.
4) Resin and glass are the two main materials used for ophthalmic lenses.
Decentration of lenses can induce unwanted prism. The amount of induced prism depends on the distance of decentration from the optical center and the power of the lens. For plus lenses, the base of the induced prism is in the direction of decentration, while for minus lenses it is in the opposite direction. Prism power can be calculated using Prentice's rule. The induced prism from decentration can have effects on binocular vision and eye alignment. Careful centration of lenses is important for optimal vision and comfort.
Vertex distance is the distance between the back surface of a corrective lens and the front of the cornea. Increasing or decreasing this distance changes the effective power of the lens. Vertex distance is important when converting between glasses and contact lens prescriptions, especially for prescriptions over +/- 4.00 diopters. The standard vertex distance is about 12mm, but individual frames may have different distances. The effective power of a lens varies with vertex distance, with plus lenses becoming stronger and minus lenses becoming weaker if the distance increases. Proper measurement of vertex distance is important for an accurate prescription.
This document discusses different types of magnification that can help low vision patients see objects more clearly. It describes relative size magnification by making objects larger, relative distance magnification by moving closer, angular magnification using optical devices, and real image magnification. The document provides examples of calculating magnification and outlines best practices for optometrists in prescribing magnification aids to patients based on their visual needs and tasks.
Frame measurements are essential for ordering prescription glasses correctly. The boxing system uses geometric center, lens size (eye size A), depth (B), and width (C) in millimeters. Distance between lenses (DBL) and geometric center distance (GCD) are also in millimeters. Temple length is overall length from center barrel to end. Frames are marked with eye size, DBL, temple length, manufacturer, and country of origin. Safety frames are marked with "Z87". Metal frames indicate gold content in karats.
Aberration and Ophthalmic Lens Design.pptJayendra Jha
This document discusses various types of optical aberrations that occur when light passes through lenses and the human eye, including chromatic aberration, spherical aberration, oblique astigmatism, coma, and image distortion. It explains how each aberration leads to imperfect image formation and describes techniques used to reduce their effects, such as using multiple lens elements made of different materials, aspheric surfaces, and the optical properties of the eye itself. The document also provides examples of tests like the duochrome test that evaluate these aberrations during eye exams.
Bifocals are lenses with two optical powers, one for distance and one for near. There are several types of bifocal segments including round, flat top, curve top, ribbon, and Franklin style. Bifocals can be made through fused, one piece, or cemented constructions. When measuring for bifocals, the frame is positioned as it will be worn and the bifocal height is measured from the lower limbus or lid margin using a vertical ruler. This ensures the bifocal segment will be at the proper height for the wearer.
The document discusses key optical concepts including aperture stops, pupils, field of view, and depth of field. It defines an aperture stop as the limiting diameter that determines the amount of light reaching the imaging area. An entrance pupil is the image of the aperture stop from the object plane, while an exit pupil is the image from the image plane. A field stop limits the size of the object that can be imaged, and vignetting occurs when rays do not pass through the entire optical system. The depth of field refers to the zone in front of and behind the focal point that appears sharp in an image.
The document discusses the history and process of manufacturing glass and lenses. It provides details on:
1) Glassmaking has been traced back to 3500 BC based on the oldest glass beads, though its discovery is unknown. Glass was initially used for jewelry before being made into art objects in 16th century BC.
2) When heated to high temperatures, sand melts and becomes glass through a molecular structure change.
3) Lens manufacturing involves measuring a patient's prescription, selecting frames, grinding lenses to the correct optical power, and fitting lenses into frames through processes like cutting, edging and mounting.
4) Resin and glass are the two main materials used for ophthalmic lenses.
Decentration of lenses can induce unwanted prism. The amount of induced prism depends on the distance of decentration from the optical center and the power of the lens. For plus lenses, the base of the induced prism is in the direction of decentration, while for minus lenses it is in the opposite direction. Prism power can be calculated using Prentice's rule. The induced prism from decentration can have effects on binocular vision and eye alignment. Careful centration of lenses is important for optimal vision and comfort.
Vertex distance is the distance between the back surface of a corrective lens and the front of the cornea. Increasing or decreasing this distance changes the effective power of the lens. Vertex distance is important when converting between glasses and contact lens prescriptions, especially for prescriptions over +/- 4.00 diopters. The standard vertex distance is about 12mm, but individual frames may have different distances. The effective power of a lens varies with vertex distance, with plus lenses becoming stronger and minus lenses becoming weaker if the distance increases. Proper measurement of vertex distance is important for an accurate prescription.
This document discusses different types of magnification that can help low vision patients see objects more clearly. It describes relative size magnification by making objects larger, relative distance magnification by moving closer, angular magnification using optical devices, and real image magnification. The document provides examples of calculating magnification and outlines best practices for optometrists in prescribing magnification aids to patients based on their visual needs and tasks.
Frame measurements are essential for ordering prescription glasses correctly. The boxing system uses geometric center, lens size (eye size A), depth (B), and width (C) in millimeters. Distance between lenses (DBL) and geometric center distance (GCD) are also in millimeters. Temple length is overall length from center barrel to end. Frames are marked with eye size, DBL, temple length, manufacturer, and country of origin. Safety frames are marked with "Z87". Metal frames indicate gold content in karats.
The Worth Four Dot Test is used to determine the presence of suppression or diplopia. It involves having the patient view four lights (one red, two green, one white) through red-green lenses. The number and configuration of lights seen indicates the type of strabismus or binocular vision status. It is an inexpensive and easy to administer test, but relies on subjective patient responses. Some studies have found it can provide reliable results even in patients with red-green color vision defects.
This document describes the process of hand neutralization to determine the power of an unknown lens. Hand neutralization involves using a lens of known power to neutralize an unknown lens, where neutralization occurs when movement of the image through the lens is eliminated, indicating the lenses have cancelling powers. The steps include drawing a cross, determining lens orientation and optical center, neutralizing each meridian by finding the lens power that eliminates movement, recording the results as a power cross, and converting to a spherocylindrical formula.
The slit lamp bimicroscope allows for high-magnification examination and evaluation of the anterior segment of the eye. It has three main components: an illumination system using a slit of light, an observation system with binocular lenses, and a mechanical system to position the eye. Various illumination techniques like diffuse, direct, and indirect can be used to examine different ocular tissues. The slit lamp has a long history and continues to be the most important tool for anterior segment evaluation, enabling detection of many abnormalities. Accessories can further aid in examination of structures like the retina, angle, and measurement of eye pressure.
This document provides information about progressive addition lenses (PALs), including their history, design, markings, fitting process, advantages, and disadvantages compared to bifocal lenses. Some key points:
- PALs were invented in the late 1950s and gradually increased in popularity as an alternative to bifocal lenses that provides clear vision from distance to near without visible lines.
- PAL designs can be "hard", with a rapid progression, or "soft" with a slower progression. Designs also differ in the size and location of distance, near, and intermediate zones.
- Fitting PALs properly requires selecting the right frame size and shape, measuring pupillary distance and fitting heights, and ver
This document describes the process of refraction using a phoropter. A phoropter is an ophthalmic testing device used to measure refractive error and determine eyeglass prescriptions. It contains different lenses. The summary describes the preliminary steps, which include positioning the patient and adjusting the device. It then outlines the 6 steps of subjective refraction: 1) test visual acuity, 2) establish spherical power, 3) refine cylindrical axis, 4) refine cylindrical power, 5) refine spherical power, and 6) perform binocular balancing.
This document discusses the uses of prisms in optometry. It begins by defining prisms and their basic properties, such as how they deviate light. It then covers prism terminology including apex, base, refracting angle, angle of deviation, and power. The document discusses how prisms cause eye movements and the resultant effects of combining prisms. It also covers induced prism from lenses, prentice's rule, and the major reference point. Finally, the summary discusses the diagnostic and therapeutic uses of prisms for conditions like convergence insufficiency and strabismus. Prisms are also used in instruments like the slit lamp and keratometer.
The document discusses the optics and use of a lensometer. A lensometer is a device used to measure the refractive power of lenses. It works using the Badal principle, where the eye is placed at the focal point of a lens and the image always subtends the same visual angle. There are manual and automated lensometers. A manual lensometer uses a telescope, target, and power drum to measure spherical and cylindrical lens powers by bringing lines of the target into focus. An automated lensometer uses an LCD monitor, lens plate, and memory buttons to electronically measure lens parameters. Correct use requires focusing the eyepiece and centering lenses to determine their optical power.
The Optics of Human Eye & Gallstrand schematic eyeHarsh Jain
The document summarizes key aspects of the human eye and optics. It describes how light stimulates vision and defines the electromagnetic spectrum. It then details the basic anatomy of the eye, including that it is divided into two chambers filled with aqueous and vitreous humor. Optics are discussed next, specifically how light enters through the cornea and pupil, is focused by the lens, and forms an image on the retina. Common refractive errors like myopia and hyperopia are also summarized. Finally, Gullstrand's schematic eye model is introduced as a simplified representation of the optical components and parameters of the typical human eye.
This document discusses various materials used in ophthalmic lenses. It describes the optical, mechanical, electrical, chemical and thermal properties of different lens materials like glass and plastics. Specifically, it provides details on the properties of different types of glass lenses including crown glass, flint glass, barium crown glass, and high index glass. It also discusses plastic lenses and highlights the use of high index lenses for higher prescriptions to reduce lens thickness.
This document summarizes standards and guidelines for ophthalmic lenses. It discusses markings that indicate lens properties like wavelength protection and tint density. Formulas are provided for determining appropriate base curves based on lens prescription, such as Vogel's formula. High powered lens designs are also outlined, including aspheric lenses for high plus powers and lenticular or myodisc designs for high minus powers to reduce edge thickness. Appropriate base curves are important for minimizing aberrations when viewing off-center.
Dynamic retinoscopy is used to objectively determine a patient's refractive error when their accommodation is active. It involves having the patient fixate on a near target while the examiner performs retinoscopy. The direction of the retinoscopic reflex indicates whether the eye is focused in front of, behind, or aligned with the retinoscope. Various methods of dynamic retinoscopy have been developed, including Monocular Estimation Method, Bell retinoscopy, and Nott retinoscopy. Dynamic retinoscopy can reveal a patient's lag of accommodation, or the difference between their accommodative response and the stimulus provided by the near target. A normal lag is between +0.50D to +0.75D.
The FDA classifies soft contact lenses into four groups based on their water content and ionic charge. Group 1 lenses have low water content and are non-ionic, while Group 2 lenses have high water content but are also non-ionic. Group 3 lenses have low water content but are ionic, and Group 4 lenses have high water content and are ionic. This classification system helps differentiate lenses' interactions with care products and their tendencies to accumulate protein deposits from tears.
Keratometry is a technique to measure the curvature of the cornea using a keratometer. A keratometer projects illuminated circles called mires onto the cornea which form reflected images. By measuring the size of the reflected images, the radius of curvature of the cornea can be calculated in two principal meridians. Keratometry is used to measure corneal astigmatism and monitor the shape of the cornea for conditions like keratoconus. Automated keratometers have replaced manual keratometers and can measure corneal curvature more quickly and accurately.
The document discusses pantoscopic tilt, which is when the bottom of eyeglass frames are angled toward the cheeks. It describes how proper pantoscopic tilt helps maximize the amount of bridge surface resting on the nose. The document also mentions retroscopic tilt, when the bottom of frames is angled away from the cheeks, and orthoscopic tilt, when frames have no angle. Additionally, it explains how lens tilt improves how glasses look and function for patients, and depends on ear and nose bridge heights, requiring frames to be properly adjusted for individual wearers before measurements.
This document provides instructions for properly ordering ophthalmic lenses. It details what information should be included in a lens order form, such as using at least three figures for the sphere and cylinder, carrying figures two places after the decimal, and specifying frame details like style and manufacturer. It also lists tips for obtaining existing lens information, such as retaking pupil distance and noting bifocal segment lines. Finally, it explains what information should be included in each numbered section of the order form.
This document provides information on various orthoptic instruments used for diagnostic and therapeutic purposes in treating binocular vision anomalies. It describes the principles, construction, procedures, and uses of several instruments including the diploscope, cherioscope, reading bars, Remy separator, Tibb's binocular trainer, and synoptophore. The diploscope and cherioscope are used to detect suppression and exercise fusion. Reading bars are home exercise devices that use physiological diplopia. The Remy separator and Tibb's trainer are haploscopic instruments used for diagnosis and treatment. The synoptophore can measure deviations, fusion, and stereopsis, and is used to treat suppression and abnormal retinal correspondence.
This document discusses the treatment of suppression and arc. It defines suppression as a cortical phenomenon that eliminates visual confusion and diplopia in strabismus. There are various types and causes of suppression. The purpose of suppression is to avoid diplopia and confusion. Treatment aims to eliminate suppression and establish binocular vision through techniques like occlusion, prism adaptation, and use of instruments like the TV trainer and bar reader that break suppression by manipulating target parameters.
The document discusses various tests used to evaluate color vision and the central visual field, including the Amsler grid and color vision charts. The Amsler grid is used to screen for macular diseases by having the patient view a grid and report any distortions, gaps, or unusual areas. Color vision tests include pseudoisochromatic plates like Ishihara plates to screen for red-green deficiencies, as well as more advanced tests like the Farnsworth-Munsell 100 Hue test to grade the severity of defects. Spectral tests like the Nagel anomaloscope are also described, which use light mixtures to accurately diagnose color vision abnormalities.
Fresnel prisms are thin, lightweight prisms that can be applied to existing spectacle lenses. They are used diagnostically to measure eye alignment and fusional reserves, and therapeutically to relieve diplopia from conditions like convergence insufficiency or small eye turnings. Fresnel prisms have advantages of thinness and flexibility but cause some visual acuity loss with higher powers. Risley prisms are a combination of two prisms that can be rotated to provide variable amounts of combined horizontal and vertical prismatic correction.
The document discusses the anatomy and optics of the human eye. It describes the main components of the eye, including the cornea, iris, lens, retina, and their functions. It also covers topics like emmetropia, refractive errors including myopia and hyperopia, their types and clinical features. Schematic and reduced eye models are introduced to conceptualize the optical properties of the eye.
The anatomy and physiology of the outer and inner eye can be summarized as follows:
1. The eyelids protect the eyeball and distribute tears across the cornea via contraction of the orbicularis muscle and opening/closing of the levator muscle.
2. The cornea refracts and transmits light, with an epithelium, stroma, and endothelial layer. The iris controls pupil size via sympathetic and parasympathetic fibers.
3. The retina converts light images to nerve impulses via photoreceptors, ganglion cells, and optic nerve fibers exiting at the optic disc. Blood vessels from the choroid and central artery supply the retina.
The Worth Four Dot Test is used to determine the presence of suppression or diplopia. It involves having the patient view four lights (one red, two green, one white) through red-green lenses. The number and configuration of lights seen indicates the type of strabismus or binocular vision status. It is an inexpensive and easy to administer test, but relies on subjective patient responses. Some studies have found it can provide reliable results even in patients with red-green color vision defects.
This document describes the process of hand neutralization to determine the power of an unknown lens. Hand neutralization involves using a lens of known power to neutralize an unknown lens, where neutralization occurs when movement of the image through the lens is eliminated, indicating the lenses have cancelling powers. The steps include drawing a cross, determining lens orientation and optical center, neutralizing each meridian by finding the lens power that eliminates movement, recording the results as a power cross, and converting to a spherocylindrical formula.
The slit lamp bimicroscope allows for high-magnification examination and evaluation of the anterior segment of the eye. It has three main components: an illumination system using a slit of light, an observation system with binocular lenses, and a mechanical system to position the eye. Various illumination techniques like diffuse, direct, and indirect can be used to examine different ocular tissues. The slit lamp has a long history and continues to be the most important tool for anterior segment evaluation, enabling detection of many abnormalities. Accessories can further aid in examination of structures like the retina, angle, and measurement of eye pressure.
This document provides information about progressive addition lenses (PALs), including their history, design, markings, fitting process, advantages, and disadvantages compared to bifocal lenses. Some key points:
- PALs were invented in the late 1950s and gradually increased in popularity as an alternative to bifocal lenses that provides clear vision from distance to near without visible lines.
- PAL designs can be "hard", with a rapid progression, or "soft" with a slower progression. Designs also differ in the size and location of distance, near, and intermediate zones.
- Fitting PALs properly requires selecting the right frame size and shape, measuring pupillary distance and fitting heights, and ver
This document describes the process of refraction using a phoropter. A phoropter is an ophthalmic testing device used to measure refractive error and determine eyeglass prescriptions. It contains different lenses. The summary describes the preliminary steps, which include positioning the patient and adjusting the device. It then outlines the 6 steps of subjective refraction: 1) test visual acuity, 2) establish spherical power, 3) refine cylindrical axis, 4) refine cylindrical power, 5) refine spherical power, and 6) perform binocular balancing.
This document discusses the uses of prisms in optometry. It begins by defining prisms and their basic properties, such as how they deviate light. It then covers prism terminology including apex, base, refracting angle, angle of deviation, and power. The document discusses how prisms cause eye movements and the resultant effects of combining prisms. It also covers induced prism from lenses, prentice's rule, and the major reference point. Finally, the summary discusses the diagnostic and therapeutic uses of prisms for conditions like convergence insufficiency and strabismus. Prisms are also used in instruments like the slit lamp and keratometer.
The document discusses the optics and use of a lensometer. A lensometer is a device used to measure the refractive power of lenses. It works using the Badal principle, where the eye is placed at the focal point of a lens and the image always subtends the same visual angle. There are manual and automated lensometers. A manual lensometer uses a telescope, target, and power drum to measure spherical and cylindrical lens powers by bringing lines of the target into focus. An automated lensometer uses an LCD monitor, lens plate, and memory buttons to electronically measure lens parameters. Correct use requires focusing the eyepiece and centering lenses to determine their optical power.
The Optics of Human Eye & Gallstrand schematic eyeHarsh Jain
The document summarizes key aspects of the human eye and optics. It describes how light stimulates vision and defines the electromagnetic spectrum. It then details the basic anatomy of the eye, including that it is divided into two chambers filled with aqueous and vitreous humor. Optics are discussed next, specifically how light enters through the cornea and pupil, is focused by the lens, and forms an image on the retina. Common refractive errors like myopia and hyperopia are also summarized. Finally, Gullstrand's schematic eye model is introduced as a simplified representation of the optical components and parameters of the typical human eye.
This document discusses various materials used in ophthalmic lenses. It describes the optical, mechanical, electrical, chemical and thermal properties of different lens materials like glass and plastics. Specifically, it provides details on the properties of different types of glass lenses including crown glass, flint glass, barium crown glass, and high index glass. It also discusses plastic lenses and highlights the use of high index lenses for higher prescriptions to reduce lens thickness.
This document summarizes standards and guidelines for ophthalmic lenses. It discusses markings that indicate lens properties like wavelength protection and tint density. Formulas are provided for determining appropriate base curves based on lens prescription, such as Vogel's formula. High powered lens designs are also outlined, including aspheric lenses for high plus powers and lenticular or myodisc designs for high minus powers to reduce edge thickness. Appropriate base curves are important for minimizing aberrations when viewing off-center.
Dynamic retinoscopy is used to objectively determine a patient's refractive error when their accommodation is active. It involves having the patient fixate on a near target while the examiner performs retinoscopy. The direction of the retinoscopic reflex indicates whether the eye is focused in front of, behind, or aligned with the retinoscope. Various methods of dynamic retinoscopy have been developed, including Monocular Estimation Method, Bell retinoscopy, and Nott retinoscopy. Dynamic retinoscopy can reveal a patient's lag of accommodation, or the difference between their accommodative response and the stimulus provided by the near target. A normal lag is between +0.50D to +0.75D.
The FDA classifies soft contact lenses into four groups based on their water content and ionic charge. Group 1 lenses have low water content and are non-ionic, while Group 2 lenses have high water content but are also non-ionic. Group 3 lenses have low water content but are ionic, and Group 4 lenses have high water content and are ionic. This classification system helps differentiate lenses' interactions with care products and their tendencies to accumulate protein deposits from tears.
Keratometry is a technique to measure the curvature of the cornea using a keratometer. A keratometer projects illuminated circles called mires onto the cornea which form reflected images. By measuring the size of the reflected images, the radius of curvature of the cornea can be calculated in two principal meridians. Keratometry is used to measure corneal astigmatism and monitor the shape of the cornea for conditions like keratoconus. Automated keratometers have replaced manual keratometers and can measure corneal curvature more quickly and accurately.
The document discusses pantoscopic tilt, which is when the bottom of eyeglass frames are angled toward the cheeks. It describes how proper pantoscopic tilt helps maximize the amount of bridge surface resting on the nose. The document also mentions retroscopic tilt, when the bottom of frames is angled away from the cheeks, and orthoscopic tilt, when frames have no angle. Additionally, it explains how lens tilt improves how glasses look and function for patients, and depends on ear and nose bridge heights, requiring frames to be properly adjusted for individual wearers before measurements.
This document provides instructions for properly ordering ophthalmic lenses. It details what information should be included in a lens order form, such as using at least three figures for the sphere and cylinder, carrying figures two places after the decimal, and specifying frame details like style and manufacturer. It also lists tips for obtaining existing lens information, such as retaking pupil distance and noting bifocal segment lines. Finally, it explains what information should be included in each numbered section of the order form.
This document provides information on various orthoptic instruments used for diagnostic and therapeutic purposes in treating binocular vision anomalies. It describes the principles, construction, procedures, and uses of several instruments including the diploscope, cherioscope, reading bars, Remy separator, Tibb's binocular trainer, and synoptophore. The diploscope and cherioscope are used to detect suppression and exercise fusion. Reading bars are home exercise devices that use physiological diplopia. The Remy separator and Tibb's trainer are haploscopic instruments used for diagnosis and treatment. The synoptophore can measure deviations, fusion, and stereopsis, and is used to treat suppression and abnormal retinal correspondence.
This document discusses the treatment of suppression and arc. It defines suppression as a cortical phenomenon that eliminates visual confusion and diplopia in strabismus. There are various types and causes of suppression. The purpose of suppression is to avoid diplopia and confusion. Treatment aims to eliminate suppression and establish binocular vision through techniques like occlusion, prism adaptation, and use of instruments like the TV trainer and bar reader that break suppression by manipulating target parameters.
The document discusses various tests used to evaluate color vision and the central visual field, including the Amsler grid and color vision charts. The Amsler grid is used to screen for macular diseases by having the patient view a grid and report any distortions, gaps, or unusual areas. Color vision tests include pseudoisochromatic plates like Ishihara plates to screen for red-green deficiencies, as well as more advanced tests like the Farnsworth-Munsell 100 Hue test to grade the severity of defects. Spectral tests like the Nagel anomaloscope are also described, which use light mixtures to accurately diagnose color vision abnormalities.
Fresnel prisms are thin, lightweight prisms that can be applied to existing spectacle lenses. They are used diagnostically to measure eye alignment and fusional reserves, and therapeutically to relieve diplopia from conditions like convergence insufficiency or small eye turnings. Fresnel prisms have advantages of thinness and flexibility but cause some visual acuity loss with higher powers. Risley prisms are a combination of two prisms that can be rotated to provide variable amounts of combined horizontal and vertical prismatic correction.
The document discusses the anatomy and optics of the human eye. It describes the main components of the eye, including the cornea, iris, lens, retina, and their functions. It also covers topics like emmetropia, refractive errors including myopia and hyperopia, their types and clinical features. Schematic and reduced eye models are introduced to conceptualize the optical properties of the eye.
The anatomy and physiology of the outer and inner eye can be summarized as follows:
1. The eyelids protect the eyeball and distribute tears across the cornea via contraction of the orbicularis muscle and opening/closing of the levator muscle.
2. The cornea refracts and transmits light, with an epithelium, stroma, and endothelial layer. The iris controls pupil size via sympathetic and parasympathetic fibers.
3. The retina converts light images to nerve impulses via photoreceptors, ganglion cells, and optic nerve fibers exiting at the optic disc. Blood vessels from the choroid and central artery supply the retina.
Refraction by the eye, schematic eye, reduced eye By kausar Alikausar Ali
The document discusses refraction in the human eye. It describes the three main refracting interfaces - the anterior corneal surface and two lens surfaces. It provides tables of refractive indices of ocular media, positions and radii of curvature of refracting surfaces based on Gullstrand's measurements. It introduces the schematic eye model and reduced eye model, listing their optical parameters including principal points, nodal points, focal lengths. It describes how the reduced eye can be used to construct retinal images and relate image size to the visual angle subtended at the nodal point.
The document discusses the optical properties of the human eye. It describes the main refractive components of the eye - the cornea and lens, their refractive indices and radii of curvature. It explains how light is refracted as it passes through these surfaces to form an image on the retina. The document also discusses the schematic eye model and how it is used to analyze the optical performance of the eye and understand aberrations like spherical aberration. Accommodation is mentioned as the process by which the lens changes shape to focus on near objects.
The document discusses the structure and function of the human eye. It describes how light enters through the cornea and pupil, and is focused onto the retina by the lens. The retina contains light-sensitive rod and cone cells which convert light into electrical signals sent to the brain via the optic nerve. Common eye diseases like myopia, hyperopia, astigmatism, glaucoma and cataracts are also outlined, as well as modern vision correction methods like contact lenses and LASIK surgery.
This document discusses key topics in space exploration including Johannes Kepler, the Hubble Space Telescope, space crafts such as the Space Shuttle and Skylab, rockets, satellites, and the International Space Station.
Optics is the study of light and its interactions with objects like mirrors, lenses, and substances that reflect, scatter, or transmit light. When light strikes an object, it can be reflected, transmitted, scattered, or absorbed. There are three main types of mirrors - plane, concave, and convex - and reflection follows the rule that the angle of incidence equals the angle of reflection. Refraction occurs when light changes speed as it passes from one medium to another, causing it to bend. Lenses use refraction to form real or virtual images depending on the position of objects in relation to the focal point.
Cardinal points are used to characterize optical systems. The six cardinal points are: focal points (primary and secondary), principal points, and nodal points. Knowing the locations of these points allows one to determine the image formed by the optical system using ray tracing. The document provides detailed explanations and diagrams of each cardinal point.
This document provides summaries of key formulas and concepts in ray optics, including:
1) Snell's law describes the relationship between the refractive indices of two media and the angle of incidence and refraction. Total internal reflection occurs when light travels from an optically dense medium to a less dense one at an angle greater than the critical angle.
2) Formulas are provided for mirror and lens formulas, linear magnification, magnification of microscopes and telescopes, and resolving power.
3) Refraction through a prism depends on the angle of incidence and angle of minimum deviation. Dispersion and angular dispersion describe how prisms separate white light into constituent colors.
This document discusses optics and the image forming mechanism of the eye. It describes the main components of the eye that contribute to its optical power, including the cornea, aqueous humour, crystalline lens, and vitreous humour. Accommodation is defined as the mechanism that allows the eye to focus on near objects and the relaxation theory of accommodation is explained. Common optical defects like myopia, hyperopia, and astigmatism are also outlined as well as presbyopia.
A schematic eye is a mathematical model that represents the basic optical features of the human eye in a simplified manner. It allows for theoretical studies of the eye as an optical instrument. There are different types of schematic eyes that range from more complex exact models to simplified models. The earliest schematic eyes were developed in the 17th-18th centuries, but the most widely used models today are based on the work of Gullstrand in the early 20th century. While schematic eyes are approximations that ignore some complexities, they provide a useful framework for calculating retinal image sizes and other optical properties of the eye.
1) The document discusses key concepts in optics, including geometrical optics, physical optics, and quantum optics.
2) Geometrical optics deals with light rays and concepts like reflection and refraction. Physical optics examines light as waves and topics such as interference and diffraction. Quantum optics views light as particles.
3) Images formed by a concave mirror depend on the object's location relative to the mirror's center of curvature and focal point. If beyond the center, the image is real, inverted, and smaller.
Implementing Section 501(r): best practices and pitfallsEY
Hospitals face a number of new disclosure and reporting requirements on Schedule H. Hear best practices and challenges, along with a practical discussion of implementation pitfalls
The document discusses the anatomy and function of the human eye. It describes the main parts of the eye including the cornea, iris, pupil, lens, ciliary muscle, vitreous humour, retina, fovea centralis, and optic nerve. It explains how each structure contributes to vision, such as how the lens bends light rays and the retina forms an image that is sent to the brain. Additionally, it provides some fun facts about eyes and tips for proper eye care.
POWERPOINT NOT MINE. CREDITS TO THE RIGHTFUL OWNER. I JUST SHARED IT HERE SO I CAN PUT A LINK TO MY BLOG. I'M TOO LAZY TO TYPE ALL THESE ONE BY ONE LOL
The human eye has several important parts that work together to allow us to see. The iris controls the amount of light entering the eye, while the lens focuses the light rays onto the retina. The retina then sends signals through the optic nerve to the brain. Rods and cones on the retina are responsible for vision in dim and bright light respectively. All parts of the eye are crucial for sight. Someone is considered blind if their vision is worse than 20/200, and there can be several causes of blindness like damage to the optic nerve or a clouded cornea.
This document contains a 25 question quiz on optics of the eye. It covers topics like the structures of the eye, their functions, refractive errors like myopia and hypermetropia, accommodation, and other eye-related concepts like cataracts and glaucoma. The questions are multiple choice with one right answer out of 5 options for each question.
Viscosity is a measure of the friction within a fluid that is shearing. It is defined as the ratio of the shear stress to the strain rate for a fluid undergoing laminar flow between two parallel plates. The viscosity determines the relationship between the shear stress and flow speed. It also determines equations like Poiseuille's equation, which relates viscosity, pressure change, and pipe radius to flow rate through a pipe. Stokes' law gives the drag force on a sphere moving through a fluid in laminar flow as proportional to viscosity and sphere velocity.
The document discusses the structure and function of the human eye. It describes the eye as similar to a camera, with components like the cornea, iris, lens, retina, and vitreous humor working together to allow vision. Light enters through the cornea and is focused by the lens onto the retina. The iris controls the size of the pupil to regulate the amount of light. Common vision defects like myopia and hyperopia are also discussed as well as how they can be corrected.
Part of Lecture series on EE321N, Power Electronics-I delivered by me during Fifth Semester of B.Tech. Electrical Engg., 2012
Z H College of Engg. & Technology, Aligarh Muslim University, Aligarh
Please comment and feel free to ask anything related. Thanks!
Blindness is a serious condition that is feared by many. Researchers are working on developing artificial vision technologies to help restore sight for the blind. One such technology is a bionic eye, which uses a camera and implant to stimulate the retina and optic nerve to generate images in the brain. The retina plays a key role in vision, containing rods, cones and ganglion cells that transmit light signals to the brain. Retinal diseases can lead to blindness by damaging these cells. Researchers are working to bypass damaged areas and provide artificial stimulation to restore some level of sight.
The document summarizes the anatomy and physiology of the retina. It describes the retina as having multiple layers that contain light-sensitive cells. These cells convert light rays into electrical signals that travel along the optic nerve to the brain. The retina contains two main areas - the posterior pole with the optic disc and macula lutea, and the peripheral retina. The macula lutea contains the fovea centralis, which has the highest concentration of light receptors and is responsible for sharp central vision. The document further details the layers of the retina, blood supply, phototransduction process of vision initiation, and dark adaptation.
Elements of visual perception Eye vision .pptxssuser7ec6af
The human visual system allows us to see and understand our environment. It consists of the eye, which contains structures like the cornea, iris, lens, retina, and specialized photoreceptor cells called rods and cones. The eye transforms light into neural signals that travel to the brain for processing. Human visual perception relies on both rods for dim light vision and cones for bright light and color vision. The density and connections of rods and cones in the retina allow for varying levels of visual acuity and light sensitivity. The lens focuses images onto the retina, where photoreceptors convert the images into signals the brain can interpret as vision.
This document provides information about the structure and function of the human eye, ear, and senses of taste and smell. It discusses:
1. The three main parts of the eye - external, immediate, and internal structures. It describes components like the cornea, iris, lens, retina, and vitreous humor.
2. The three parts of the ear - outer, middle, and inner ear. It notes the functions of the eardrum, three tiny bones, and cochlea in hearing.
3. The definition of sensation and overview of the gustatory (taste) and olfactory (smell) senses, noting the role of taste buds and receptors in the nose.
The visual pathway/visual system is the part of central nervous system which gives organisms the ability to process visual detail , as well as enabling the formation of several non-image photo response functions.
It detects interprets information from visible light to build a representation of the surrounding environment .
The visual system carries out a number of complex tasks , including the reception of light and the formation of monocular representations; the buildup of a nuclear binocular perception from a pair of two dimensional projections ; the identification and categorization of visual objects ; assessing distances to and between objects and guiding body movements in relation to the objects seen.
2. Anatomy and physiology of the eye.pptYerkeNurlybek
The orbit contains and protects the eye. It is formed by seven bones and surrounded by nasal sinuses. The optic nerve passes through the optic foramen to the orbit.
The eye has six extraocular muscles - four recti and two obliques. All are supplied by the oculomotor nerve except the superior oblique and lateral rectus.
The main refractive structures are the cornea and lens. The cornea is the main refracting structure and the lens can change its power of accommodation. The iris determines eye color. Opacification of the lens is called cataract.
The macula is the central part of the retina containing the fovea and foveola. The optic
The eye is composed of three layers - the fibrous tunic, vascular tunic, and retina. The fibrous tunic includes the sclera and transparent cornea. The vascular tunic contains the choroid, ciliary body, and iris. The retina lines the inside of the eye and contains light-sensitive rod and cone cells. Light passes through the cornea and lens and strikes the retina, where it is converted to nerve signals sent to the brain via the optic nerve. The iris controls the size of the pupil to regulate light entry. Various structures work together to focus light and maintain the eye's shape and pressure.
The document discusses the anatomy and function of the human eye. It describes how the eye has evolved over 50 million years from tree-dwelling ancestors into its modern form. The eye functions similarly to a camera, using a lens to focus light and specialized cells in the retina to process visual images that are sent to the brain. Understanding how the eyes, retina and brain work together allows us to better interpret visual messages and cues communicated through eye contact and expression.
VISION IN ANIMALS VETERINARY PHYSIOLOGY.pdfTatendaMageja
This document provides an overview of canine vision anatomy and physiology. It describes the key structures of the eye, including the retina, iris, lens, cornea, and optic nerve. It explains how light enters the eye and is detected by photoreceptors in the retina. The visual signals are then transmitted through the retina and optic nerve to the brain for processing. Features like the pupil, lens curvature, and presence of the fovea centralis in some species enhance vision. The document also discusses conditions like Horner's syndrome that can affect the eye's function.
The document summarizes the structure and function of the human eye. It describes the three layers that make up the eyeball - fibrous, vascular and nervous layers. The fibrous layer includes the sclera and cornea. The vascular layer includes the choroid, ciliary body and iris. The nervous layer is the retina. It also explains key parts of the eye like the iris, lens, vitreous humor and aqueous humor. The retina contains photoreceptors that convert light to neural signals sent to the brain via the optic nerve. The visual pathway and common refractive errors are also summarized.
he sense organs — eyes, ears, tongue, skin, and nose — help to protect the body. The human sense organs contain receptors that relay information through sensory neurons to the appropriate places within the nervous system.
Each sense organ contains different receptors.
General receptors are found throughout the body because they are present in skin, visceral organs (visceral meaning in the abdominal cavity), muscles, and joints.
Special receptors include chemoreceptors (chemical receptors) found in the mouth and nose, photoreceptors (light receptors) found in the eyes, and mechanoreceptors found in the ears.
The document provides detailed information about the anatomy and physiology of the human eye. It includes labeled diagrams and descriptions of the major parts of the eye such as the cornea, iris, lens, retina, optic nerve and their functions. It also explains common eye conditions that can occur when certain parts are damaged or not functioning properly, such as cataracts, glaucoma and macular degeneration.
The human color vision describes about The Cornea, The Sclera/ Sclerotic coat, The Pupil, The Retina, The Choroid Coat, The vitreous humor, The aqueous humor, The lens, Foveal Pit, Yellow Spot, Blind Spot, How the Human Eye Works, The Rods, The Cone Cells, Types of Cones, Spectral sensitivity, Defective color vision/ Color blindness, Symptoms of Color Blindness, Causes of Color Blindness, Trichromates, Dichromates, Monochromates, Anomalous Trichromates.
The human eye is a camera-type eye that focuses light onto the retina. The cornea and crystalline lens work together to focus incoming light, with the ciliary muscles helping to change the lens shape to focus on near or far objects. Light passes through the lens and vitreous humor before striking the light-sensitive retina, where it is converted to electrical signals and sent to the brain for interpretation. Common vision problems include nearsightedness, farsightedness, astigmatism, and presbyopia, which often develops in middle age as the lens stiffens.
The document summarizes key aspects of vision and the eye's anatomy and physiology. It discusses:
1) How light stimulates vision by interacting with photoreceptors in the retina.
2) The main parts of the eye including the cornea, iris, lens, pupil, sclera, and retina containing rods and cones.
3) How photoreceptors (rods and cones) absorb light and transmit signals to bipolar and ganglion cells which form the optic nerve sending signals to the brain.
The document summarizes the anatomy and physiology of the special senses, focusing on vision and hearing. It describes:
1) The accessory structures of the eye that facilitate vision like the eyelids, conjunctiva, and lacrimal glands.
2) The three layers that make up the walls of the eyeball - fibrous tunic, vascular tunic, and sensory tunic containing photoreceptors.
3) How sound waves are collected by the outer ear, amplified by the middle ear bones, and transduced into nerve impulses in the inner ear for hearing.
The document outlines the anatomy and examination of the head and neck region. It describes the bones, muscles, nerves, blood vessels and structures of the eyes, ears, nose, mouth, throat and neck. Key points include identifying the cranial nerves involved in vision and hearing, describing visual field defects and causes of abnormal eye movements. Examination techniques are covered such as visual acuity tests, otoscopy, lymph node palpation and assessment of the thyroid gland. The overall goal is to teach students to obtain a relevant history and perform a complete physical exam of the head and neck.
structure and fuction of eyes and ears,types of memory,sharpe memory,attentionUmarKhan422
The document discusses the structure and function of the eye and ear and their importance in daily life. It provides detailed descriptions of the main parts of the eye including the cornea, iris, lens, retina, etc. and explains their functions. It also discusses the main parts of the ear like the outer, middle and inner ear and how they work together to detect and transmit sound to the brain. Finally, it outlines several important uses of vision and hearing in daily life like communication, enjoyment, safety and more and emphasizes the importance of managing hearing loss.
Sliding Mode Control (SMC) is a type of Variable Structure Control that uses a discontinuous control law to drive the system states towards a switching surface, called the sliding surface, in finite time, resulting in robust behavior to disturbances and uncertainties. The summary discusses:
1) SMC involves selecting a sliding surface and designing discontinuous feedback gains such that the system trajectory intersects and stays on the sliding surface.
2) For a sliding mode to exist, the system state trajectory velocity must always be directed towards the sliding surface in its vicinity.
3) Using Lyapunov stability analysis, sufficient conditions are presented to guarantee the existence of a sliding mode and that the sliding surface is reached in finite
The document provides details on the history of US ballistic missile defense programs from 1944 to present day. It discusses early programs like Project Nike and Safeguard that tracked missiles. It then covers the Strategic Defense Initiative from the 1980s which conducted tests like Homing Overlay Experiments demonstrating intercepts. Subsequent programs tested interceptors like the ERIS, HEDI, and Ground Based Interceptor. The document also provides information on various radars used for detection and tracking like Cobra Dane, PAVE PAWS, and Sea-Based X-Band Radar.
10 fighter aircraft avionics - part iiiSolo Hermelin
This document provides a summary of fighter aircraft avionics across different generations of fighter jets. It discusses the avionics systems of third, fourth, 4.5 and fifth generation fighters. Specific avionics components covered include cockpit displays, communication systems, data entry/control, flight control, navigation, sensors and weapons systems. The document also discusses topics related to aircraft performance, flight instruments, propulsion and aerodynamics as they relate to fighter jet avionics.
This document provides a summary of fighter aircraft avionics and flight instruments. It discusses the basic variables that represent the thermodynamic state of air including density, temperature, and pressure. It then describes key flight instruments such as the altimeter, airspeed indicator, and how the air data computer uses total and static pressure and temperature readings to calculate important flight parameters. The roles of the pitot-static system and various gyroscopic and magnetic instruments are also summarized.
The document summarizes the history and development of gyro gunsights used in aircraft from World War 2 through the Cold War. Gyro gunsights automatically calculated the lead angle and bullet drop needed for a pilot to hit a moving target. The first operational gyro gunsight was the British Mark I in 1941. Improved models like the Mark II saw widespread use through the end of WWII. Germany developed the EZ 42 gyro sight but it did not see full deployment. The US developed the AN/ASG-26 for the F-4 Phantom, which provided targeting information via a head-up display.
The document is a table of contents for a publication about cutaway diagrams of modern aircraft from around the world. It lists over 130 aircraft from countries like the US, USSR/Russia, UK, France, Sweden, China, Iran, and Israel. The table of contents is divided into sections for different manufacturers and countries. It provides brief 1-2 word descriptions of aircraft like the F-14, F-16, Mirage 2000, MiG-21, and Su-27.
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
2. 2
Table of Content
SOLO Optics - Eye
Human Eye Introduction
Human Eye Structure
Retina
Rods and Cones
Facts and Figures concerning the human retina
Human Eye Optics
Introduction to Lenses and Geometrical Optics
Waves and Rays
Optical Aberration
Common Vision Defects and Their Correction
Aberrometers
Color Blindness
Microscope Optical Components- Introduction
Eyepieces (Oculars)
References
The Lens
3. 3
SOLO Optics - Eye
http://www.olympusmicro.com/primer/anatomy/introduction.html
Human Eye Introduction
4. 4
SOLO Optics - Eye
Human Eye Introduction
http://www.olympusmicro.com/primer/anatomy/numaperture.html
6. 6
SOLO Optics - Eye
The visual pathway: from the eyes to the brain’s visual cortex (adapted from Gray 1918)
Human Eye Structure
7. 7
SOLO Optics - Eye
Structure of the eye from Hecht, Optics
The human eye is able to detect from about 390 to
780 nanometers, defining the visual spectrum
8. 8
SOLO Optics - Eye
1=Iris The colored part of the eye located between the
Lens and Cornea. It regulates the entrance of the light.
2 = Cornea The transparent, blood-free tissue covering
the central front of the eye that initially refracts or bends
light rays as light enters the eye. Contact lenses are fitted
over the Cornea.
3 = Retina The innermost layer of the eye, a
neurological tissue, which receives light rays focused on
it by the Lens. This tissue contains receptor cells (Rods
and Cones) that send electrical impulses to the brain via
the optic nerve when the light rays are present.
4 = Rods The receptor cells which are sensitive to light
and are located in the Retina of the eye. They are
responsible for night vision, as non-color vision in low
level light.
5 = Cones The receptor cells which are sensitive to light
and are located in the Retina of the eye. They are
responsible for color vision.
6 = Lens The eye's natural Lens. Transparent, biconvex
intraocular tissue that helps bring rays of light to a focus
on the Retina.
7 = Pupil The opening at the center of the Iris of the eye.
It contracts in a high level of light and when the eye is
focused on a distant object.
Human Eye Structure
21. SOLO Optics - Eye
The vertebrate retina is a light sensitive tissue lining the inner surface of the eye. The optics of
the eye create an image of the visual world on the retina, which serves much the same
function as the film in a camera. Light striking the retina initiates a cascade of chemical and
electrical events that ultimately trigger nerve impulses. These are sent to various visual
centers of the brain through the fibers of the optic nerve.
In vertebrate embryonic development, the retina and
the optic nerve originate as outgrowths of the
developing brain, so the retina is considered part of
the central nervous system (CNS). It is the only part
of the CNS that can be imaged non-invasively in the
living organism.
Retina
The retina is a complex, layered structure with several layers of neurons interconnected by
synapses. The only neurons that are directly sensitive to light are the photoreceptor cells. These
are mainly of two types: the rods and cones. Rods function mainly in dim light and provide
black-and-white vision, while cones support daytime vision and the perception of colour. A
third, much rarer type of photoreceptor, the photosensitive ganglion cell, is important for
reflexive responses to bright daylight.
Neural signals from the rods and cones undergo complex processing by other neurons of
the retina. The output takes the form of action potentials in retinal ganglion cells whose
axons form the optic nerve. Several important features of visual perception can be traced
to the retinal encoding and processing of light.
22. SOLO Optics - Eye
Retina
Anatomy of vertebrate retina
The vertebrate retina has ten distinct layers. From
innermost to outermost, they include:
1.Inner limiting membrane - Müller cell footplates
2.Nerve fiber layer
3.Ganglion cell layer - Layer that contains nuclei of
ganglion cells and gives rise to optic nerve fibers.
4.Inner plexiform layer
5.Inner nuclear layer contains bipolar cells
6.Outer plexiform layer - In the macular region, this
is known as the Fiber layer of Henle.
7.Outer nuclear layer
8.External limiting membrane - Layer that separates
the inner segment portions of the photoreceptors from
their cell nuclei.
9.Photoreceptor layer - Rods / Cones
10.Retinal pigment epithelium
24. SOLO Optics - Eye
Retina
Retina's simplified axial organization. The
retina is a stack of several neuronal layers.
Light is concentrated from the eye and passes
across these layers (from left to right) to hit the
photoreceptors (right layer). This elicits
chemical transformation mediating a
propagation of signal to the bipolar and
horizontal cells (middle yellow layer). The signal
is then propagated to the amacrine and ganglion
cells. These neurons ultimately may produce
action potentials on their axons. This
spatiotemporal pattern of spikes determines the
raw input from the eyes to the brain. (Modified
from a drawing by Ramón y Cajal.)
In adult humans the entire retina is approximately
72% of a sphere about 22 mm in diameter. The
entire retina contains about 7 million cones and 75
to 150 million rods. An area of the retina is the optic
disc, sometimes known as "the blind spot" because
it lacks photoreceptors. It appears as an oval white
area of 3 mm². Temporal (in the direction of the
temples) to this disc is the macula. At its center is
the fovea, a pit that is most sensitive to light and is
responsible for our sharp central vision. Human
and non-human primates possess one fovea as
opposed to certain bird species such as hawks who
actually are bifoviate and dogs and cats who possess
no fovea but a central band known as the visual
streak. Around the fovea extends the central retina
for about 6 mm and then the peripheral retina. The
edge of the retina is defined by the ora serrata. The
length from one ora to the other (or macula), the
most sensitive area along the horizontal meridian is
about 3.2 mm.
25. SOLO Optics - Eye
Retina
In section the retina is no more than 0.5 mm thick. It has three layers of nerve cells and two of
synapses, including the unique ribbon synapses. The optic nerve carries the ganglion cell axons to
the brain and the blood vessels that open into the retina. The ganglion cells lie innermost in the
retina while the photoreceptive cells lie outermost. Because of this counter-intuitive arrangement,
light must first pass through and around the ganglion cells and through the thickness of the retina,
(including its capillary vessels,not shown) before reaching the rods and cones. However it does not
pass through the epithelium or the choroid (both of which are opaque).
The white blood cells in the capillaries in front of the photoreceptors can be perceived as tiny bright
moving dots when looking into blue light. This is known as the blue field entopic phenomenon (or
Scheerer's phenomenon).
Between the ganglion cell layer and the rods and cones there are two layers of neuropils where
synaptic contacts are made. The neuropil layers are the outer plexiform layer and the inner
plexiform layer. In the outer the rods and cones connect to the vertically running bipolar cells,
and the horizontally oriented horizontal cells connect to ganglion cells.
The central retina is cone-dominated and the peripheral retina is rod-dominated. In total there are
about seven million cones and a hundred million rods. At the centre of the macula is the foveal pit
where the cones are smallest and in a hexagonal mosaic, the most efficient and highest density.
Below the pit the other retina layers are displaced, before building up along the foveal slope until
the rim of the fovea or parafovea which is the thickest portion of the retina. The macula has a
yellow pigmentation from screening pigments and is known as the macula lutea. The area directly
surrounding the fovea has the highest density of rods converging on single bipolars. Since the
cones have a much lesser power of merging signals, the fovea allows for the sharpest vision the eye
can attain.
38. SOLO Optics - Eye
1.Rods
The vast majority of the cells on the retina
Panchromatic -- sensitive to wide range of wavelengths.
But not energy/color-discriminating within this range: Receptors translate all light to
same "signal" = amount of light.
Thus, delivers "shades of gray", like a high speed, black and white film.
The specific chemical that makes rods active is rhodopsin, a complex protein with a
40,000 amu atomic weight, which makes up as much as 35% of the cell dry weight.
Absorption curve of rhodopsin shown roughly by the curve
Absorption of the photon splits off a small, 264 amu
fragment (a chromophore) called retinaldehyde (a
derivative of Vitamin A), and instantaneously one of the
double bonds changes from a cis to a trans type bond.
Remainder of protein is called opsin.
39. SOLO Optics - Eye
1.Rods (continue – 1)
In a process not well understood, splitting of protein changes permeability of the neuron's
membrane to sodium ions, which changes the electrical potential of the cell.
Change in potential propagates through nerve cells to transmit message to brain.
Between 1 to 10 photons must be absorbed to "trigger" particular rod (similar to
photographic grains in film).
However, rods are bundled to a single nerve fiber, so act together.
Slowly (over 30 min timescale), the full rhodopsin molecule is regenerated.
Rods concentrated to outer part of retina.
Completely missing in the 0.3 mm diameter fovea centralis, in
center of yellow patch called the macula.
Note the image of the full moon on retina is only
0.2mm.
Night blindness occurs when there is damage to the
outer part of the retina.
Normal vision (left and right) and night blindness (middle),
from http://www.retina-international.org/nightbld.htm.
40. SOLO Optics - Eye
2.Cones
About 5% of the retinal cells.
Probably work same way as rods, but contain slightly different iodopsin protein with the
retinaldehyde group.
As a group, provide sensitivity to colors.
Translate color sensation to brain.
From three different kinds we achieve color sensitivity.
42. SOLO Optics - Eye
The RED sensitivity for the R-cones
or the L-cones
Range from 410 to 690 nanometer
Peak 580 nm
Peak range from 558 to 580 nm
The GREEN sensitivity for the G-cones
or the M-cones
Range from 440 to 670 nm
Peak 540 nm
Peak range from 534 to 540 nm
The BLUE sensitivity for the B-cones
or the S-cones
Range from 400 to 540 nanometer
Peak 440 nm
Peak range from 420 to 440 nm
Three Types of Cones:
L, M, S
44. SOLO Optics - Eye
Facts and Figures concerning the human retina
1.Size of the retina
32mm from ora to ora along the horizontal meridian (Van
Buren, 1963; Kolb, unpublished measurements). Area of the
human retina is 1094 square mm (Bernstein, personal
communication) calculated from the expectations that the
average dimension of the human eye is 22 mm from anterior to
posterior poles, and that 72% of the inside of the globe is retina
(Michels et al., 1990).
2.Size of optic nerve head or disc.
1.86x 1.75 mm
3.Degrees and distance in micometers.
One degree of visual angle is equal to 288 µm on the retina without correction for shrinkage
(Drasdo and Fowler (1974).
4.Foveal position.
11.8o
or or 3.4 mm temporal to the optic disk edge
5.Cross diameter of the macula.
3mm of intense pigmentation, surrounded by 1 mm wide zone of less pigmentation
(Polyak, 1941).
45. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 1)
6.Cross diameter of the central fovea from foveal rim to foveal rim.
1.5mm (Polyak, 1941)
1.2-1.5mm (Ahnelt and Kolb, unpublished data)
7.Cross diameter of central rod free area.
400-600µm (Polyak, 1941)
750µm (Hendrickson and Youdelis, 1984)
570µm (Yamada, 1969)
250µm (Ahnelt et al., 1987)
8.Vertical thickness of the fovea from ILM to ELM.
In the foveal pit 150 µm (Yamada, 1969)
foveal rim 300 µm
9.Length of foveal axons (Henle fibers).
150-300µm (Ahnelt and Pflug, 1986).
46. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 2)
10.Vertical thickness of the retina in different areas.
The vertical extent of the retina across the horizontal meridian at
different eccentricities is shown in Figure 3. This is taken from data
given by Sigelman and Ozanics (1982). The small black numbers
are the originals from Sigelman and Ozanics which were measured
in typical histological preparations where there is a great deal of
shrinkage. The figures in red are those recently measured by Ahnelt
(personal communication) in well fixed EM quality material where
there is little or no shrinkage. Hence the latter numbers are larger.
The numbers are in mm.
47. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 3)
11.Age when fovea is fully developed.
Not before 4 years of age (Hendrickson and Youdelis, 1984).
12.Highest density of cones at center of the fovea
(counted in a 50 x 50 µm square).
147,000/mm2
(Osterberg, 1935)
178,000-238,000/mm2
(Ahnelt et al., 1987)
96,900-281,000/mm2
mean161,900/mm2
(Curcio et al., 1987).
13.Total number of cones in fovea.
Approximately 200,000. There are 17,500 cones/degree2
.
Rod free area is approximately 1o
thus there are 17,500
cones in the central rod-free fovea.
14.Total number of cones in the retina.
6,400,000(Osterberg, 1935).
15.Total number of rods in the retina.
110,000,000to 125,000,000 (Osterberg, 1935).
48. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 4)
16.Rod distribution
Rods peak in density 18o
or 5mm out from the center of the
fovea in a ring around the fovea at 160,000 rods/mm2
. (Fig. 5)
No rods in central 200 µm.
Average 80-100,000 rods/mm2
Rod acuity peak is at 5.2o
or 1.5 mm from foveal center
where there are 100,000 rods/mm2
(Mariani et al.,1984).
17.Number of axons in the optic nerve.
564776-1,140,030(Bruesch and Arey, 1942)
800,000-1,000,000(Polyak, 1941)
1,200,000(Quigley et al., 1982; Balaszi et al., 1984).
18.Number of cones to ganglion cells in the fovea.
1cone to 2 ganglion cells out to about 2.2o
(Schein, 1988).
19.Number of cones/retinal pigment epithelial cell (RPE).
30cones/RPE in fovea (Rapaport et al., 1995).
49. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 5)
20.Number of rods/retinal epithelial cell (RPE).
In periphery 22 rods/RPE cell
In rod peak (4-5 mm from foveal center) 28 rods/RPE cell
(Rapaport et al.,1995).
50. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 6)
21.Number of neural and glial types in the retina.
The retina consists of many millions of cell types packed together in a
tightly knit network spread over the surface of the back of the eye fundus
as a thin film of tissue only 1/2 millimeter thick. The retina is like a
three layered cake with three layers containing cell bodies of neurons
and two filling layers where synapses betwen the neurons occur. There
are two basic kinds of photoreceptors, rods and cones. The cones are
further subdivided into two types (long and short wavelength sensitive)
in the majority of mammals, i.e. most mamals are dichromats and have
divariant color vision. In primates a third wavelength sensitive cone has
developed closely related to the long wavelength cone type but a little
more sensitive in the middle wavelength (i.e. green cone). Thus primates
including man are trichromats and have trivariant color vision. Many
reptiles, birds and fish have 4 or even 5 types of cone each sensitive to a
slightly different peak wavelength.
The second order neurons postsynaptic to the photorecepors in the first synaptic
(filling layer) (outer plexiform layer) are bipolar cells and horizontal cells. There
are 9 types of bipolar cell and 2 to 4 types of horizontal cell in species from
mammals to fish. The third order neurons are amacrine cells and ganglion cells
that synapse in the inner synaptic filling layer (inner plexiform layer). There are
two types of interplexiform cell stretching between both plexiform layers, in most
vertebrate retinas.There are approximately 22 types of amacrine cell and 20 types
of ganglion cell in the typical mammalian retina. There may be 30 or more
amacrine cell types in fish and reptilian retinas and 22 or so ganglion cell types.
The increased number of third order neurons is due to the greater information
processing taking place in the non mammalian retinas that in mammalian.
51. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 7)
22.Useful Units in Vision Science (Wandell, 1995).
Radiometric units represent a physical measurement e.g., radiance is measured in watts sr -1 m-2.
Calorimetric units adjust radiometric units for visual wavelength sensitivity e.g., luminance
is measured in candela per square meter, cd/m2.
Lux are units of illumination. Thus a light intensity of 1 candela produces an illumination of
1 lux at 1 meter.
Scotopic luminance units are proportional to the number of photons absorbed by rod
photoreceptors to give a criterion psychophysical result.
Photopic luminance units are proportional to a weighted sum of the photons absorbed by L- and
M-cones to give a criterion psychophysical result.
Typical ambient luminance levels (cd/m2):.
Starlight: 0.001
Moonlight: 0.1
Indoor lighting: 100
Sunlight: 10.000
Maximum intensity of common CRT monitors: 100
One Troland (Td) of retinal illumination is produced when an eye with a pupil size of 1 mm2
looks at a surface whose luminance is 1 cd/m2.
Lens focal length: f(meters); lens power= 1/f (diopters).
52. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 8)
23.Image formation (Wandell, 1995).
The eyes are 6 cm apart and halfway down the head.
Visual angle of common objects (degrees, deg)
The sun or moon = 0.5 deg
Thumbnail (at arm's length) = 1.5 deg
Fist (at arm's length) = 8-10 deg
Visual field (measured from central fixation)
Monocular: 160 deg (w) x 175 deg (h)
Binocular: 200 deg (w) x 135 deg (h)
Region of binocular overlap: 120 deg (w) x 135 deg (h)
Range of pupil diameters: 1-8 mm.
Refractive indices
Air: 1.000
Glass: 1.520
Water: 1.333
Cornea: 1.376
53. SOLO Optics - Eye
Facts and Figures concerning the human retina (continue - 9)
23.Image formation (Wandell, 1995) (continue – 1).
Optical power (diopters).
Cornea: 43
Lens (relaxed): 20
Whole eye: 60
Change in power due to accomodation: 8
Axial chromatic aberration over the visible spectrum: 2 diopters.
Visible spectrum: 370-730 nanometers (nm)
Peak wavelength sensitivity:
Scotopic: 507 nm
Photopic: 555 nm
Spectral equilibrium hues:
Blue: 475 nm
Green: 500 nm
Yellow: 575 nm
No spectral equilibrium: red
61. SOLO
converging beam
=
spherical wavefront
parallel beam
=
plane wavefront
Image Plane
Ideal Optics
P'
Optical Aberration
converging beam
=
spherical wavefront
Image Plane
Ideal Optics
diverging beam
=
spherical wavefront
P
P'
An Ideal Optical System can be defined by one of the three different and equivalent ways:
All the rays emerging from a point source P, situated at a finite or infinite distance
from the Optical System, will intersect at a common point P’, on the Image Plane.
3
All the rays emerging from a point source P will travel the same Optical Path to reach
the image point P’.
2
The wavefront of light, focused by the Optical System on the Image Plane, has a
perfectly spherical shape, with the center at the Image point P.
1
Ideal Optical System
62. SOLO
ideal wavefrontparallel beam
=
plane wavefront
Image Plane
Non-ideal Optics
aberrated beam
=
iregular wavefront
diverging beam
=
spherical wavefront
aberrated beam
=
irregular wavefront
Image Plane
Non-ideal Optics
ideal wavefront
Optical Aberration
Real Optical System
An Aberrated Optical System can be defined by one of the three different and equivalent
ways:
The rays emerging from a point source P, situated at a finite or infinite distance
from the Optical System, do not intersect at a common point P’, on the Image Plane.
3
The rays emerging from a point source P will not travel the same Optical Path to reach
the Image Plane
2
The wavefront of light, focused by the Optical System on the Image Plane, is not
spherical.
1
63. Optical Aberration W (x,y) is the path deviation between the distorted and reference
Wavefront.
SOLO Optical Aberration
64. SOLO Optical Aberration
Display of Optical Aberration W (x,y)
Rays Deviation3
Optical Path Length Difference2
wavefront shape W (x,y)1
Red circle denotes the pupile margin.
Arrows shows how each ray is deviated
as it emerges from the pupil plane.
Each of the vectors indicates the the
local slope of W (x,y).
The aberration W (x,y) is
represented in x,y plane by
color contours.
x
y
( )yxW ,
Wavefront
Error
x
y
( )yxW ,
Optical
Distance
Errors
x
y
Ray
Errors
The Wavefront error agrees with
Optical Path Length Difference,
But has opposite sign because a
long (short) optical path causes
phase retardation (advancement).
Aberration Type:
Negative vertical
coma
Reference
65. SOLO Optical Aberration
Display of Optical Aberration W (x,y)
Advanced phase <= Short optical
path
Retarded phase <= Long optical
path
Reference
Ectasia
x
y
Ray Errors
y
( )yxW ,
x
Optical Distance Errors
x
y
( )yxW ,
Wavefront Error
66. SOLO
Real Imaging Systems
Departures from the idealized conditions of Gaussian Optics in a real Optical System are
called Aberrations
Monochromatic Aberrations
Chromatic Aberrations
• Monochromatic Aberrations
Departures from the first order theory are embodied
in the five primary aberrations
1. Spherical Aberrations
2. Coma
3. Astigmatism
4. Field Curvature
5. Distortion
This classification was done in 1857
by Philipp Ludwig von Seidel (1821 – 1896)
• Chromatic Aberrations
1. Axial Chromatic Aberration
2. Lateral Chromatic Aberration
Optical Aberration
67. SOLO
Real Imaging Systems
Seidel Aberrations Distortions of the Wavefront
( ) θθθθ cos''cos'cos'';, 32222234
rhCrhCrhCrhCrChrW DiFCAsCoSp ++++=
Optical Aberration
68. 68
SOLO OPTICS
Common Optical Defects in Lens Systems (Aberrations)
http://www.olympusmicro.com/primer/anatomy/numaperture.html
69. SOLO Optics
Zernike’s Polynomials
In 1934 Frits Zernike introduces a complete set of orthonormal polynomials
to describe aberration of any complexity.
( ) ( ) ( ) ( )θρθρθρ
m
N
m
n
m
n
m
nN YRaZZ == ,,
,2,1
2
813
min =
++−
= N
N
Integern
( ) ( ) { }
−
=
−++
−=
oddN
evenN
msign
Nnn
Integernm
1
1
4
212
min2
Each polynomial of the Zernike set is a product of
three terms.
where
( )
≠+
=+
=
012
01
mifn
mifn
a
m
n
( ) ( ) ( )
( )[ ] ( )[ ]
( )
sn
mn
s
s
m
n
smnsmns
sn
R 2
2/
0 !2/!2/!
!1 −
−
=
∑ −−−+
−−
= ρρ
( )
≠
≠
=
=
oddisNandmif
evenisNandmif
mif
Y
m
N
0sin
0cos
01
θ
θθ
radial index
meridional
index
70. SOLO Optics
Zernike’s Polynomials
Properties of Zernike’s Polynomials.
( ) ( )∑∑=
n m
m
n
m
n ZCW θρθρ ,,
W (ρ,θ) – Waveform Aberration
Cn
m
(ρ,θ) – Aberration coefficient (weight)
Zn
m
(ρ,θ) – Zernike basis function (mode)
( ){ } ( ) mallnallforZZMean
m
n
m
n 00,, >== θρθρ1
( ){ } mnallforZVariance
m
n ,1, =θρ2
3 Zernike’s Polynomials are mutually orthogonal, meaning that they are independent
of each other mathematically. The practical advantage of the orthogonality is that
we can determine the amount of defocus, or astimagtism, or any other Zernike mode
occurring in an aberration function without having to worry about the presence of
the other modes.
4 The aberration coefficients of a Zernike expansion are analogous to the Fourier
coefficients of a Fourier expansion.
( ){ } ( ) ( )[ ] ( )∑∑∑∑ =
−=
n m
m
n
n m
m
n
m
n
m
n CZZCMeanWVariance
2
2
,,, θρθρθρ
( ) ( )
( ) '
1
0
'
12
1
nn
m
n
m
n
n
dRR δρρρρ
+
=∫ ( ) '0
2
0
1'coscos mmmdmm δδπθθθ
π
+=∫
71. SOLO Optics
Zernike’s Polynomials
In 1934 Frits Zernike introduces a complete set of orthonormal polynomials
to describe aberration of any complexity.
Astigmatism
{ }4,4,,2 22
−− ayax
Coma1
{ }3,5,,2 2
−+ axaxρ
Coma2
{ }4,4,,2 2
−+ ayaxρ
Spherical&
Defocus
( ) { }3,5,,3.12 22
−+ aaρρ
36Zernikes
Geounyoung Yoon, “Aberration Theory”
76. 76
SOLO Optics - Eye FIGURE 127: Top left, optical power (in diopters)
of the two main elements of the human eye, cornea
and crystalline lens (number in brackets is
corresponding f.l. if imaging in air; for the eye as a
whole, assuming a single imaging element with
22.2mm f.l. effective in the aqueous medium).
Top right, a graph showing approximate size of the
aberrated blur relative to the diffraction blur (Airy
disc diameter). Absolute blur size is at the minimum
for ~2mm pupil diameter. For larger pupils, blur is
enlarged due to eye aberrations, and for smaller
pupils due to diffraction. At large pupil openings,
dominant aberration component is roughness, as
can be seen from the right-most diffraction pattern.
It shows what an actual pattern at 5mm pupil may
look like, not one appropriate to the ray spot.
Change in the nominal size of the blur is much less
pronounced than the change relative to the Airy
disc.
Ray spots show axial blur for F, e and C spectral
lines at 1mm, 2mm and 5mm pupil diameter
(SPEC'S) of the eye model used). Longitudinal
chromatism is nearly constant at about 0.3mm of
axial defocus between F and C; relative to the Airy
disc (black circle), transverse chromatism changes
with the square of the pupil diameter. Hence, it is at
the level of a 4" f/12 achromat for about 3mm pupil
diameter. Both, diffraction and aberrated blurs are
relatively large with respect to the cones (~2μ-10μ)
and rods (~2.5μ-5μ), so it is diffraction and
aberrations that determine retinal image quality.
http://www.telescope-optics.net/eye_aberrations.htm
Eye Aberration
80. SOLO OPTICS
Aberrometers
A number of technical and practical parameters that may be useful in choosing an
aberrometer for daily clinical practice.
The main focus is on wavefront measurements, rather than on their possible
application in refractive surgery. The aberrometers under study are the following:
1.Visual Function Analyzer (VFA; Tracey): based on
ray tracing; can be used with the EyeSys Vista corneal topographer.
2.OPD-scan (ARK 10000; Nidek): based on automatic retinoscopy; provides
integrated corneal topography and wavefront measurement in 1 device.
3.Zywave (Bausch & Lomb): a Hartmann-Shack system that can be combined
with the Orbscan corneal topography system.
4.WASCA (Carl Zeiss Meditec): a high-resolution Hartmann-Shack system.
5.MultiSpot 250-AD Hartmann-Shack sensor: a custom-made Hartmann-Shack
system, engineered by the Laboratory of Adaptive Optics at Moscow State
University, that includes an adaptive mirror to compensate for accommodation
6.Allegretto Wave Analyzer (WaveLight): an objective Tscherning device
81. SOLO OPTICS
Aberrometers
Figure 1. The principles of the wavefront
sensors:
Top: Skew ray.
Center Left: Ray tracing.
Center Right: Hartmann-Shack.
Bottom Left: Automatic retinoscope.
Bottom Right: Tscherning.
Single-head arrows indicate direction
of movement for beams.
Figure 2. Reproductions of the fixation targets for the
patient: A: VFA.B: OPD-scan. C: Zywave. D: WASCA.
E: MultiSpot. F: Allegretto.
82. SOLO
OPTICSAberrometers
Johannes Hartmann
1865-1936
In 1920, an astrophysicist named Johannes Hartmann devised
a method of measuring the ray aberration of mirrors and lenses.
He wanted to isolate rays of light so that they could be traced and any
imperfection in the mirror could be seen. The Harman Test consist on
using metal disk in which regulary spaced holes had been drilled.
The disk or screen was then placed over the mirror that was to be tested
and a photographic plate was placed near the focus of the mirror. When
exposed to light, a perfect mirror will produce an image of regulary
spaced dots. If the mirror does not produce regularly spaced dots, the
irregularities, or aberrations, of the mirror can be determined.
Figure 1. Optical schematic for an early
Hartmann test.
Schematic from Santa Barbara Instruments Group (SBIG)
software for analysis of Hartmann tests.
1920
83. SOLO OPTICS
Optical schematic for first Shack-Hartmann sensor.
Around 1971 , Dr. Roland Shack and Dr. Ben Platt advanced the concept replacing
the screen with a sensor based on an array of tiny lenselets. Today, this sensor is known
as the Hartmann - Shack sensor. Hartmann – Shack sensors are used in a variety of
industries: military, astronomy, ophthalmogy.
Schematic showing Shack-Hartmann CCD output.
Schematic of Shack-Hartmann data analysis process.
Hartmann - Shack Aberrometer
Roland Shack
1971
84. SOLO OPTICS
Lenslet array made by Heptagon
for ESO. The array has 40 x 40
lenslets, each 500 μm (0.5 mm) in
size.
Part of lenslet array made by WaveFront Sciences.
Each lens is 144 μm in diameter.
Hartmann - Shack Aberrometer
85. SOLO OPTICS
Hartmann - Shack Aberrometer
Recent image from Adaptive
Optics Associates (AOA) shows
the optical set-up used to test
the first Shack-Hartmann
sensor.
Upper left) Array of images
formed by the lens array from a
single wavefront.
Upper right) Graphical
representation of the wavefront
tilt vectors.
Lower left) Zernike polynomial
terms fit to the measured data.
Lower right) 3-D plot of the
measured wavefront.
90. Color TheorySOLO
Color Blindness
Normal Color Vision Red-Blind/Protanopia Green-Blind/Deuteranopia
Blue-Blind/Tritanopia
Blue-Weak/Tritanomaly
Red-Weak/Protanomaly Green-Weak/Deuteranomaly
Monochromacy/Achromatopsia Blue Cone Monochromacy
91. SOLO Color Theory 1917
Shinobu Ishihara
(1879--1963)
Shinobu Ishihara created the Ishihara Color Test to detect
Color Blindness.
The Ishihara Color Blindness test – named after a
Japanese Professor at the University of Tokyo – is the most
well known tool to test for red-green color blindness. Mr
Ishihara developed this test almost 100 years ago. It was
first published in 1917 and is used since then to check if
someone is suffering from protanopia or deuteranopia, the
two different kinds of red-green color vision deficiencies.
A collection of 38 plates filled with colored dots build the
base of this test. The dots are colored in different shades of
a color and a number or a line is hidden inside with
different shades of an other color. But enough theory, take
the color blindness test by Mr Ishihara yourself and be
surprised (or not) of the result.
A plate from the Ishihara Test for color
blindness. Can you see the number 74? However,
whether you see the number or not, don’t take
this as a final indication: it is only one plate of
many plates in the full test and the colors on
your computer screen might not be exactly right.
A plate from the Ishihara Test for color blindness. Can
you see the number 12?
103. 103
SOLO
References
OPTICS
1. Waldman, G., Wootton, J., “Electro-Optical Systems Performance Modeling”,
Artech House, Boston, London, 1993
2. Wolfe, W.L., Zissis, G.J., “The Infrared Handbook”, IRIA Center,
Environmental Research Institute of Michigan, Office of Naval Research, 1978
3. “The Infrared & Electro-Optical Systems Handbook”, Vol. 1-7
4. Spiro, I.J., Schlessinger, M., “The Infrared Technology Fundamentals”,
Marcel Dekker, Inc., 1989
http://www.cs.bgu.ac.il/~icbv07/LectureNotes/ICBV-Lecture-Notes-12-Sensing-2
-The-Human-Eye-1SPP.pdf
http://www.olympusmicro.com/primer/anatomy/numaperture.html
Austin Roorda, PhD, “Optics Waveform”, University of Houston, College of Optometry
104. 104
SOLO
References
Foundation of Geometrical Optics
[3] E.Hecht, A. Zajac, “Optics ”, 3th
Ed., Addison Wesley Publishing Company, 1997,
[4] M.V. Klein, T.E. Furtak, “Optics ”, 2nd
Ed., John Wiley & Sons, 1986
105. 105
SOLO
References
[1] M. Born, E. Wolf, “Principle of Optics – Electromagnetic Theory of Propagation,
Interference and Diffraction of Light”, 6th
Ed., Pergamon Press, 1980,
[2] C.C. Davis, “Laser and Electro-Optics”, Cambridge University Press, 1996,
OPTICS
106. January 5, 2015 106
SOLO
Technion
Israeli Institute of Technology
1964 – 1968 BSc EE
1968 – 1971 MSc EE
Israeli Air Force
1970 – 1974
RAFAEL
Israeli Armament Development Authority
1974 – 2013
Stanford University
1983 – 1986 PhD AA