Retro illumination
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This document discusses retro-illumination techniques used during ophthalmic examinations. Retro-illumination involves illuminating the object of interest using light reflected from structures behind it. It can be used to assess the pupils and transparent ocular media, and to observe whether any opacities are obstructive, refractive, or refractile. Direct retro-illumination views the observed structure in the direct path of reflected light, while indirect retro-illumination views the structure against a dark background. Retro-illumination allows visualization of features like vascularization, edema, microcysts, and contact lens deposits.
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- It provides quantitative indices like simulated keratometry and maps of corneal power, elevation, and irregularity to evaluate corneal shape.
- Pentacam is useful for diagnosing conditions like keratoconus by detecting thinning, steepening, and irregularity. It can also evaluate outcomes of procedures like refractive surgery and intraocular surgery.
- Clinical applications include pre-op screening, surgical planning, contact lens fitting, and determining refraction.
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- 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.
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Vertex distance and power
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- It provides quantitative indices like simulated keratometry and maps of corneal power, elevation, and irregularity to evaluate corneal shape.
- Pentacam is useful for diagnosing conditions like keratoconus by detecting thinning, steepening, and irregularity. It can also evaluate outcomes of procedures like refractive surgery and intraocular surgery.
- Clinical applications include pre-op screening, surgical planning, contact lens fitting, and determining refraction.
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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
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Retinoscopy is the primary objective method for determining a patient's refractive error. It involves using a retinoscope to illuminate the retina and observe the movement of the reflected light. For myopic patients, the light moves in the opposite direction of the retinoscope's movement, while for hyperopic patients it moves in the same direction. The goal is to find the neutralization point where no movement is seen, indicating the proper refractive correction. Factors like the working distance, type of mirror used, and patient's fixation can impact results. Retinoscopy is useful for initial refractive estimates and screening for ocular conditions.
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Physiology of sight
Light enters the eyes and is focused on the retina. The retina contains light-sensitive rod and cone cells that detect light and allow vision. Rods function in low light and provide black and white vision while cones require bright light and enable color vision. For clear vision, the lens, pupil size, convergence of the eyes, and accommodation must be coordinated to focus images on the retina. Binocular vision from both eyes allows depth perception.
Optics & Refraction-Dr.PrabhatDevkota.pptx
This document provides an overview of optics and refraction. It defines key terminology like refraction, reflection, interference, diffraction, and polarization. It describes the refractive components of the eye including the cornea, lens, vitreous, and their optical properties. It discusses refractive states like emmetropia, myopia, hyperopia, and astigmatism. It also covers objective refraction techniques like retinoscopy which involves illuminating the retina and observing the light reflex in the pupil to determine a person's refractive error.
Slit lampbiomicroscopy-jinal & dhara
The slit lamp allows examination of the anterior segment of the eye and provides magnified views. It has three main components: an illumination system using a slit beam of light, an observation system with microscope, and a mechanical system. Different illumination techniques like diffuse, direct, retroillumination are used to examine various structures. The slit lamp is used for diagnostic evaluation of many anterior segment diseases and procedures like gonioscopy, pachymetry and contact lens fitting. It provides detailed examination of structures like cornea, iris, angle and anterior chamber.
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The pupil is a circular opening in the iris that controls the amount of light entering the eye. It constricts (miosis) and dilates (mydriasis) under autonomic nervous system influence. The iris contains two muscle groups - the sphincter pupillae and dilator pupillae - that regulate pupil size. Abnormal pupils may be unequal in size (anisocoria), irregularly shaped, or have abnormal reactions to light or accommodation. Various diseases and drugs can cause pupil abnormalities.
eye.pptx
- The eye has three principal layers: an outer fibrous layer, middle vascular layer, and inner nervous layer.
- The middle layer contains the choroid, ciliary body, and iris. The iris regulates the intensity of light entering the eye.
- The inner layer contains the retina, which has photoreceptors (rods and cones) that detect light and transmit signals to the brain.
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This presentation discusses retinoscopy, which is an objective method of determining refractive error by neutralizing the movement of light reflected from the retina. The history, theory, procedure, and types of retinoscopy are explained. Static retinoscopy finds the far point, while dynamic retinoscopy assesses accommodation. Observations of the retinoscopic reflex indicate refractive errors, and neutralization with lenses determines the prescription. Potential sources of error and techniques to confirm astigmatism are also reviewed.
Pupil
The pupil is a circular opening located in the center of the iris that controls the amount of light entering the eye. It constricts (miosis) and dilates (mydriasis) under autonomic nervous system influence. The iris contains two sets of muscles - the sphincter pupillae contracts the pupil in response to parasympathetic stimulation while the dilator pupillae dilates it with sympathetic stimulation. Abnormal pupils may be unequal in size (anisocoria), irregularly shaped, or have abnormal reactions to light. Various diseases and drugs can affect the pupils.
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Retro illumination
- 1. RETRO-ILLUMINATION Manahan, Maclester T. OP 1-1
- 2. Retro-illumination Object of interest is illuminated only by light reflected from the structures behind it.
- 3. Vary angle of illumination Moderately wide beam Slit beam is offset Medium to high magnification Reflected light from iris or fundus
- 4. Objectives 1. Assessment of pupils and all parts of the transparent ocular media (tear film, cornea, aqueous, lens, and vitreous). 2. Used to observe whether the opacity is -Obstructive – Opaque to light -Respersive – Scatters light -Refractile – Refracts, minimizes or distorts the views of background. 3. Observe anterior capsular changes -Deposits, Foreign bodies, Opacities Below Capsule.
- 5. Procedure direct retro-illumination: The observed feature on the cornea is viewed in the direct pathway of reflected light. The angle between the microscope and the illuminating arm is about 60°. indirect retro-illumination: The angle between the microscope and slit-lamp arms is greatly reduced or increased so that the feature on the cornea is viewed against a dark background. It may be necessary to uncouple the beam.
- 6. Alignment of reflected beam with area under observation TYPE ALIGNMENT Direct Direct and full view Indirect Adjacent Marginal Margin or edge
- 7. Direct Retro-illumination Look to the side of the corneal block Objects viewed may have one color in direct and a different color with retroillumination.
- 8. The object (observed structure) is viewed in the direct pathway of the reflected light. The illuminated background is directly behind the observed structure. direct retro-illumination
- 10. The object (observed structure) is not viewed in the direct pathway of the reflected light. The retro-illumination object is viewed against a dark non-illuminated background. The reflecting illuminated surface is to one side of the axis of observation. observed structure
- 11. observing: Vascularization Epithelial oedema Microcysts Vacuoles Dystrophies Crystalline lens opacities Contact lens deposits
- 12. Limbal Injection Limbal vessel engorgement seen with retroillumination and very high magnification. This may be a prelude to vascularization.
- 13. Vascularization Vascular ingrowth into the cornea arising from a vaso-proliferative stimulus..Observe the looping and branching limbal vessels seen against the illuminated background of the clear cornea.
- 14. Jelly Bumps Lipoidal deposition on the lens surface, common with high water content hydrogel lenses.
- 15. findings: Expected absence of: Vascularization Epithelial oedema Microcysts Vacuoles Bullae Dystrophies Crystalline lens opacities Contact lens deposits
- 16. tђคภк ץ๏ย