Keratoconus is a progressive eye disease where the cornea thins and bulges into a cone shape. It is diagnosed based on a patient's visual complaints and examination findings showing corneal thinning and irregularity. Treatment progresses from glasses and rigid contact lenses for mild cases. For more advanced cases, corneal collagen crosslinking may be used to stop progression, and INTACS ring segments or corneal transplantation may be needed to improve vision. The main types of transplantation are deep anterior lamellar keratoplasty and penetrating keratoplasty.
The document discusses Pentacam, a diagnostic tool that uses a rotating Scheimpflug camera to capture 50 images in 2 seconds and create a 3D model of the anterior eye segment. It has applications in assessing corneal ectasia, refractive surgery, corrected intraocular pressure, corneal aberrations, IOL power calculation, and densitometry. The Pentacam provides curvature, pachymetry, and elevation maps. It can detect ectasia by identifying if the highest curvature, thinnest thickness, and steepest elevation points coincide. The Pentacam is also used to measure corneal aberrations via Zernike analysis and calculate accurate IOL power for patients with previous refractive surgery or cataracts.
This document discusses astigmatism, presbyopia, and aphakia. It defines these conditions and describes their causes, symptoms, diagnosis, and treatment options. For astigmatism, it covers the different types including regular and irregular astigmatism. It discusses tests like keratometry and retinoscopy. Treatment includes optical correction with lenses, refractive surgery procedures, and intraocular lenses. For presbyopia, it defines the condition as age-related loss of accommodation. Symptoms and onset with age are described. Treatment involves optical correction with single vision, bifocal, or multifocal lenses as well as contact lenses and refractive surgery options.
Multiple Choice Questions (MCQs) for Masters of Optometry Entrance Examinatio...RabindraAdhikary
Multiple Choice Questions (MCQs) for Masters of Optometry Entrance Examination, Pokhara University NEPAL
MCQs Optometry Nepal
Here we have included syllabus of entrance examinations for Master of Optometry in Pokhara University, entry requirements of candidate for the master of optometry course and multiple choice questions that appeared in the entrance examinations of 2019.
Prepared by: Rabindra Adhikary
for more MCQs:
http://ravinems.blogspot.com/2019/05/multiple-choice-questions-mcqs-for.html
Corneal physiology in relation to contact lens wearHira Dahal
This document discusses corneal physiology in relation to contact lens wear. It describes the layers of the cornea and its blood, nerve and oxygen supply. Maintaining corneal transparency requires adequate oxygen and metabolism. Contact lenses reduce oxygen levels, which can cause swelling, hypoesthesia, and structural changes if levels fall below what the cornea requires. The minimum oxygen needed varies from 5-17.9% depending on the activity. Soft lenses induce more swelling than RGP lenses. Hypoxia affects epithelial healing, sensitivity and metabolism.
Ideal Properties
Provides sufficient oxygen
Optically transparent
Stable dimensions
Good wettability
Resists spoliation
Easily machinable
Easy to manufacture
Physical Properties
Wettability : ability of the tears to form complete film over then lens surface
Flexibility : highly flexible material will contour to the cornea
Optical quality : optically homogenous and transparent
Bicompatibility : should not induce any inflammatory or immunological responses.
Manufacturing ease : easy and cost effective
Stable parameters : dimensionally stable and easily polished.
This document discusses measurement of fusion and stereopsis in binocular vision. It begins by defining binocular vision and binocular single vision. It then discusses various classifications, prerequisites, advantages, and related terms of binocular single vision. The document also describes different tests used to measure fusion, including the synaptophore, prism fusion test, Worth's four dot test, Bagolini's striated glass test, and Maddox rod test. It provides details on the procedures and interpretations of these tests. Finally, it discusses the development and grades of binocular vision.
A 20-year-old Saudi female presented with progressive gradual loss of vision in both eyes over two years. Examination found VA of 6/9 in the right eye and 6/18 in the left. Signs of keratoconus were seen including stromal thinning, Vogt's striae, and Munson's sign. Topography showed patterns characteristic of keratoconus such as inferior steepening and asymmetric bowtie patterns. She was diagnosed with keratoconus stage 2 based on findings. Contact lenses were recommended for management as spectacles could not adequately correct her vision.
Keratoconus is a progressive eye disease where the cornea thins and bulges into a cone shape. It is diagnosed based on a patient's visual complaints and examination findings showing corneal thinning and irregularity. Treatment progresses from glasses and rigid contact lenses for mild cases. For more advanced cases, corneal collagen crosslinking may be used to stop progression, and INTACS ring segments or corneal transplantation may be needed to improve vision. The main types of transplantation are deep anterior lamellar keratoplasty and penetrating keratoplasty.
The document discusses Pentacam, a diagnostic tool that uses a rotating Scheimpflug camera to capture 50 images in 2 seconds and create a 3D model of the anterior eye segment. It has applications in assessing corneal ectasia, refractive surgery, corrected intraocular pressure, corneal aberrations, IOL power calculation, and densitometry. The Pentacam provides curvature, pachymetry, and elevation maps. It can detect ectasia by identifying if the highest curvature, thinnest thickness, and steepest elevation points coincide. The Pentacam is also used to measure corneal aberrations via Zernike analysis and calculate accurate IOL power for patients with previous refractive surgery or cataracts.
This document discusses astigmatism, presbyopia, and aphakia. It defines these conditions and describes their causes, symptoms, diagnosis, and treatment options. For astigmatism, it covers the different types including regular and irregular astigmatism. It discusses tests like keratometry and retinoscopy. Treatment includes optical correction with lenses, refractive surgery procedures, and intraocular lenses. For presbyopia, it defines the condition as age-related loss of accommodation. Symptoms and onset with age are described. Treatment involves optical correction with single vision, bifocal, or multifocal lenses as well as contact lenses and refractive surgery options.
Multiple Choice Questions (MCQs) for Masters of Optometry Entrance Examinatio...RabindraAdhikary
Multiple Choice Questions (MCQs) for Masters of Optometry Entrance Examination, Pokhara University NEPAL
MCQs Optometry Nepal
Here we have included syllabus of entrance examinations for Master of Optometry in Pokhara University, entry requirements of candidate for the master of optometry course and multiple choice questions that appeared in the entrance examinations of 2019.
Prepared by: Rabindra Adhikary
for more MCQs:
http://ravinems.blogspot.com/2019/05/multiple-choice-questions-mcqs-for.html
Corneal physiology in relation to contact lens wearHira Dahal
This document discusses corneal physiology in relation to contact lens wear. It describes the layers of the cornea and its blood, nerve and oxygen supply. Maintaining corneal transparency requires adequate oxygen and metabolism. Contact lenses reduce oxygen levels, which can cause swelling, hypoesthesia, and structural changes if levels fall below what the cornea requires. The minimum oxygen needed varies from 5-17.9% depending on the activity. Soft lenses induce more swelling than RGP lenses. Hypoxia affects epithelial healing, sensitivity and metabolism.
Ideal Properties
Provides sufficient oxygen
Optically transparent
Stable dimensions
Good wettability
Resists spoliation
Easily machinable
Easy to manufacture
Physical Properties
Wettability : ability of the tears to form complete film over then lens surface
Flexibility : highly flexible material will contour to the cornea
Optical quality : optically homogenous and transparent
Bicompatibility : should not induce any inflammatory or immunological responses.
Manufacturing ease : easy and cost effective
Stable parameters : dimensionally stable and easily polished.
This document discusses measurement of fusion and stereopsis in binocular vision. It begins by defining binocular vision and binocular single vision. It then discusses various classifications, prerequisites, advantages, and related terms of binocular single vision. The document also describes different tests used to measure fusion, including the synaptophore, prism fusion test, Worth's four dot test, Bagolini's striated glass test, and Maddox rod test. It provides details on the procedures and interpretations of these tests. Finally, it discusses the development and grades of binocular vision.
A 20-year-old Saudi female presented with progressive gradual loss of vision in both eyes over two years. Examination found VA of 6/9 in the right eye and 6/18 in the left. Signs of keratoconus were seen including stromal thinning, Vogt's striae, and Munson's sign. Topography showed patterns characteristic of keratoconus such as inferior steepening and asymmetric bowtie patterns. She was diagnosed with keratoconus stage 2 based on findings. Contact lenses were recommended for management as spectacles could not adequately correct her vision.
Astigmatism is a refractive error where the refraction varies in different meridians, causing light rays to focus as lines rather than points on the retina. There are two main types: regular astigmatism where refractive power changes uniformly between meridians, and irregular astigmatism where changes are irregular. Regular astigmatism is classified based on the axis of the two principal meridians as with-the-rule, against-the-rule, or oblique. Symptoms include blurred vision, eyestrain, and tilting of the head, and it is diagnosed through retinoscopy, keratometry, and astigmatic tests. Treatment involves prescribing cylindrical lenses through glasses or contacts.
Aberrometry is a technique used to measure optical aberrations in the eye by analyzing wavefronts. There are two main types of aberration: lower order aberrations, which can be corrected using prescriptions like for myopia and astigmatism, and higher order aberrations involving the eye's inability to create a perfect image. Aberrometry is used for refractive surgery planning, contact lens fitting, diagnosing conditions like keratoconus, and improving vision by correcting aberrations. Commercial aberrometers use principles like Scheiner's disk, Shack-Hartmann lenslet arrays, and ray tracing to measure the wavefront distortion caused by a patient's optical aberrations.
This presentation describes all the clinical aspects of keratoconus management
You can watch the illustrated presentation in this link :
https://www.youtube.com/watch?v=pYxwZPGm7e4&list=PLZ_mM13I_TrhWavjTmE9NjW1O5bGxkONO&index=13
The document discusses keratoconus, a non-inflammatory thinning of the cornea. It is mostly bilateral and affects girls aged 15-20, causing visual impairment due to irregular astigmatism. Keratoconus is classified into four stages based on criteria like corneal curvature and thickness. Various theories for its causes are discussed, including enzymes, genetics, eye rubbing. Clinical features include corneal protrusion, thinning, Fleischer's ring, and scarring in advanced cases. Diagnosis involves tools like keratometry, topography and pachymetry to assess curvature, thickness and irregularity. Treatment options include glasses, contact lenses fitted using different techniques, and surgeries like collagen crosslinking and keratoplasty for
The document discusses Pentacam corneal topography. Some key points:
- Pentacam uses Scheimpflug imaging to obtain images of the anterior segment and measure the shape of the cornea.
- 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.
Subjective refraction techniques rely on the patient's response to determine the refractive correction that provides the best visual acuity. Determining the astigmatic correction is more complex than just the spherical error. Different techniques are used, including the cross-cylinder method and clock dial method. For the cross-cylinder method, the axis is refined first followed by the cylinder power to get the best visual acuity. For children, cycloplegic refraction is important and the full refractive error should typically be corrected, though sometimes undercorrection may be used initially.
The document describes the use of various Pentacam maps and indices for screening patients for keratoconus, including:
1) The standard 4-map composite report, keratoconus map, Holladay report, and Belin/Ambrosio Enhanced Ectasia Display.
2) Key features to examine on each map include anterior and posterior elevation maps, pachymetry maps, curvature maps, and indices values.
3) The Belin/Ambrosio Enhanced Ectasia Display aims to improve sensitivity by calculating an "enhanced" best fit sphere reference surface that excludes the thinnest corneal region, highlighting differences between normal and ectatic corneas.
The basis of manual small incision cataract surgery is the tunnel construction for entry to the anterior chamber.
The parameters important for the structural integrity of the tunnel are the self-sealing property of the tunnel, the location of the wound on the sclera with respect to the limbus, and the shape of the wound.
Cataract surgery has gone beyond just being a means to get the lens out of the eye.
Postoperative astigmatism plays an important role in the evaluation of final outcome of surgery. Astigmatic consideration, hence, forms an integral part of incisional considerations prior to surgery.
The document describes the Amsler grid chart, which was developed in 1920 by Dr. Marc Amsler to test for central vision disorders. It consists of a grid pattern with white lines on a black background that is used to evaluate the macula. Patients are asked a series of questions while viewing the chart to check for blurriness, distortions, or missing areas that could indicate conditions like macular degeneration or retinal detachment. The document outlines the purposes and procedures for several variations of the Amsler grid and provides instructions for patients to perform self-examinations at home in order to monitor eye conditions.
This document discusses several tests that can be used to detect suppression in patients:
1. The four dot test uses red-green glasses and a light with red, green, and white dots to see if the patient reports more than one light.
2. The Striated Lens Test uses special lenses with striations at different angles to see if the patient perceives a full X pattern of light or missing lines, indicating suppression.
3. The base-out prism test checks for suppression by placing prisms in front of one eye to see if the eyes make an adjustment to the shifted image or not.
4. The Brock string uses differently colored beads on a string to see if the patient
Cataract surgery in special situations by Dr. Iddi.pptxIddi Ndyabawe
This document discusses cataract surgery in special situations. It covers considerations for combined cataract extraction and glaucoma surgery, cataract surgery in patients with high myopia, uveitis, small pupils, mature cataracts, diabetes, and Fuchs endothelial dystrophy. Key factors include preoperative evaluation, managing increased risks during surgery such as weak zonules or poor visibility, and postoperative care to prevent complications related to the underlying conditions. Surgical techniques are adapted based on the situation, such as using pupil expansion devices, minimizing phaco power, or coating the endothelium with viscoelastic.
This document provides color coding guidelines for documenting corneal conditions. Black is used to outline structures and indicate scars, thinning, and nerves. Red denotes blood vessels, growths, lacerations, and congestion. Brown is used for pigmentation, rings, and old conditions. Yellow indicates pigmentation, deposits, infiltrates, and cataracts. Green represents defects, filaments and edema. Blue shows overall edema, folds, and blisters. Precise documentation using these color codes allows for standardization, easy follow-up and teaching regarding various corneal pathologies.
Orthokeratology, also known as corneal reshaping therapy, uses specially designed contact lenses to temporarily reshape the cornea and reduce or eliminate refractive errors. It allows patients to have clear unaided vision for most of the day by modifying the corneal curvature through overnight lens wear. Studies have shown orthokeratology can slow the progression of myopia in children by an average of 50%. A trial fitting is performed to assess the fluorescein pattern and ensure proper centration, bearing, and tear reservoir before beginning overnight wear to achieve the desired refractive change. Orthokeratology provides an alternative to glasses or surgery and is reversible.
Interpretation of visual fields with special reference to octopusHaitham Al Mahrouqi
The document provides an overview of visual field interpretation using the Octopus perimeter. It discusses what a visual field is, why they are important, and types of perimetry including static and kinetic. It describes advantages of different test strategies like TOP and SITA fast that can reduce test time. Key aspects of the Octopus 7-in-1 printout are outlined including demographic data, reliability indices, threshold values compared to norms, and mean deviation and pattern deviation plots.
This document discusses esotropia, or convergent strabismus. It describes the different types of esotropia including concomitant and incomitant deviations. It further categorizes esotropia as accommodative or non-accommodative. Early-onset esotropia developing within the first 6 months is discussed in detail, including typical clinical features and management with early surgical alignment and treatment of amblyopia and refractive error. Subsequent development of inferior oblique overaction and dissociated vertical deviation are also addressed.
This document discusses the application of anterior segment optical coherence tomography (AS-OCT) in diagnosing various ocular conditions. It provides an overview of AS-OCT imaging principles and compares it to ultrasound biomicroscopy. The document then examines the use of AS-OCT in diagnosing and monitoring conditions of the cornea, conjunctiva, and anterior chamber angle/glaucoma. Examples of pathologies that can be identified include corneal scars, Fuchs' dystrophy, graft rejection, angle closure, and bleb assessment after glaucoma surgery.
This document discusses the diagnosis of pre-perimetric glaucoma. It begins by defining pre-perimetric glaucoma as optic nerve abnormalities seen on structural tests with normal visual fields. It then discusses the need for early diagnosis before functional changes occur. Various functional tests are described like standard automated perimetry, short wavelength automated perimetry, frequency doubling technology, and others. Structural tests like confocal scanning laser ophthalmoscopy, optical coherence tomography, and their principles are summarized.
The document discusses corneal tomography parameters and their significance in evaluating post-refractive surgery eyes and detecting ectatic disorders. It provides normal values and characteristics for pachymetry, keratometry, sagittal and elevation maps, and other Pentacam parameters. Abnormal findings that may indicate conditions like keratoconus and pellucid marginal degeneration are also described.
This document discusses the anatomy and development of the vitreous humor in the eye. It begins by describing the embryological origin of vitreous cells from surface ectoderm, neuroectoderm, and mesodermal tissues. During the primary vitreous stage, the vitreous body begins forming before closure of the choroidal fissure and appears as a fibrillated secretion filling the vitreous space. The document then covers the general features, structure including hyaloid layers, cortical and medullary regions, attachments, composition and transport processes of the mature vitreous humor. It concludes by describing the physicochemical properties and factors affecting expansion and contraction of the vitreous gel.
UBM and ASOCT provide high-resolution cross-sectional images of the anterior segment including the cornea, anterior chamber, angle, and iris. ASOCT uses optical coherence tomography with a wavelength of 1310nm for improved penetration and reduced retinal damage compared to posterior segment OCT. It allows high-speed imaging of dynamic structures. ASOCT has applications in assessing corneal diseases and procedures, glaucoma (including angle anatomy and iridotomy evaluation), and intraocular lens implantation. Measurements of angle width parameters help evaluate angle closure risk. While valuable for objective angle assessment, ASOCT cannot image all anatomical structures involved in glaucoma.
Astigmatism is a refractive error where the refraction varies in different meridians, causing light rays to focus as lines rather than points on the retina. There are two main types: regular astigmatism where refractive power changes uniformly between meridians, and irregular astigmatism where changes are irregular. Regular astigmatism is classified based on the axis of the two principal meridians as with-the-rule, against-the-rule, or oblique. Symptoms include blurred vision, eyestrain, and tilting of the head, and it is diagnosed through retinoscopy, keratometry, and astigmatic tests. Treatment involves prescribing cylindrical lenses through glasses or contacts.
Aberrometry is a technique used to measure optical aberrations in the eye by analyzing wavefronts. There are two main types of aberration: lower order aberrations, which can be corrected using prescriptions like for myopia and astigmatism, and higher order aberrations involving the eye's inability to create a perfect image. Aberrometry is used for refractive surgery planning, contact lens fitting, diagnosing conditions like keratoconus, and improving vision by correcting aberrations. Commercial aberrometers use principles like Scheiner's disk, Shack-Hartmann lenslet arrays, and ray tracing to measure the wavefront distortion caused by a patient's optical aberrations.
This presentation describes all the clinical aspects of keratoconus management
You can watch the illustrated presentation in this link :
https://www.youtube.com/watch?v=pYxwZPGm7e4&list=PLZ_mM13I_TrhWavjTmE9NjW1O5bGxkONO&index=13
The document discusses keratoconus, a non-inflammatory thinning of the cornea. It is mostly bilateral and affects girls aged 15-20, causing visual impairment due to irregular astigmatism. Keratoconus is classified into four stages based on criteria like corneal curvature and thickness. Various theories for its causes are discussed, including enzymes, genetics, eye rubbing. Clinical features include corneal protrusion, thinning, Fleischer's ring, and scarring in advanced cases. Diagnosis involves tools like keratometry, topography and pachymetry to assess curvature, thickness and irregularity. Treatment options include glasses, contact lenses fitted using different techniques, and surgeries like collagen crosslinking and keratoplasty for
The document discusses Pentacam corneal topography. Some key points:
- Pentacam uses Scheimpflug imaging to obtain images of the anterior segment and measure the shape of the cornea.
- 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.
Subjective refraction techniques rely on the patient's response to determine the refractive correction that provides the best visual acuity. Determining the astigmatic correction is more complex than just the spherical error. Different techniques are used, including the cross-cylinder method and clock dial method. For the cross-cylinder method, the axis is refined first followed by the cylinder power to get the best visual acuity. For children, cycloplegic refraction is important and the full refractive error should typically be corrected, though sometimes undercorrection may be used initially.
The document describes the use of various Pentacam maps and indices for screening patients for keratoconus, including:
1) The standard 4-map composite report, keratoconus map, Holladay report, and Belin/Ambrosio Enhanced Ectasia Display.
2) Key features to examine on each map include anterior and posterior elevation maps, pachymetry maps, curvature maps, and indices values.
3) The Belin/Ambrosio Enhanced Ectasia Display aims to improve sensitivity by calculating an "enhanced" best fit sphere reference surface that excludes the thinnest corneal region, highlighting differences between normal and ectatic corneas.
The basis of manual small incision cataract surgery is the tunnel construction for entry to the anterior chamber.
The parameters important for the structural integrity of the tunnel are the self-sealing property of the tunnel, the location of the wound on the sclera with respect to the limbus, and the shape of the wound.
Cataract surgery has gone beyond just being a means to get the lens out of the eye.
Postoperative astigmatism plays an important role in the evaluation of final outcome of surgery. Astigmatic consideration, hence, forms an integral part of incisional considerations prior to surgery.
The document describes the Amsler grid chart, which was developed in 1920 by Dr. Marc Amsler to test for central vision disorders. It consists of a grid pattern with white lines on a black background that is used to evaluate the macula. Patients are asked a series of questions while viewing the chart to check for blurriness, distortions, or missing areas that could indicate conditions like macular degeneration or retinal detachment. The document outlines the purposes and procedures for several variations of the Amsler grid and provides instructions for patients to perform self-examinations at home in order to monitor eye conditions.
This document discusses several tests that can be used to detect suppression in patients:
1. The four dot test uses red-green glasses and a light with red, green, and white dots to see if the patient reports more than one light.
2. The Striated Lens Test uses special lenses with striations at different angles to see if the patient perceives a full X pattern of light or missing lines, indicating suppression.
3. The base-out prism test checks for suppression by placing prisms in front of one eye to see if the eyes make an adjustment to the shifted image or not.
4. The Brock string uses differently colored beads on a string to see if the patient
Cataract surgery in special situations by Dr. Iddi.pptxIddi Ndyabawe
This document discusses cataract surgery in special situations. It covers considerations for combined cataract extraction and glaucoma surgery, cataract surgery in patients with high myopia, uveitis, small pupils, mature cataracts, diabetes, and Fuchs endothelial dystrophy. Key factors include preoperative evaluation, managing increased risks during surgery such as weak zonules or poor visibility, and postoperative care to prevent complications related to the underlying conditions. Surgical techniques are adapted based on the situation, such as using pupil expansion devices, minimizing phaco power, or coating the endothelium with viscoelastic.
This document provides color coding guidelines for documenting corneal conditions. Black is used to outline structures and indicate scars, thinning, and nerves. Red denotes blood vessels, growths, lacerations, and congestion. Brown is used for pigmentation, rings, and old conditions. Yellow indicates pigmentation, deposits, infiltrates, and cataracts. Green represents defects, filaments and edema. Blue shows overall edema, folds, and blisters. Precise documentation using these color codes allows for standardization, easy follow-up and teaching regarding various corneal pathologies.
Orthokeratology, also known as corneal reshaping therapy, uses specially designed contact lenses to temporarily reshape the cornea and reduce or eliminate refractive errors. It allows patients to have clear unaided vision for most of the day by modifying the corneal curvature through overnight lens wear. Studies have shown orthokeratology can slow the progression of myopia in children by an average of 50%. A trial fitting is performed to assess the fluorescein pattern and ensure proper centration, bearing, and tear reservoir before beginning overnight wear to achieve the desired refractive change. Orthokeratology provides an alternative to glasses or surgery and is reversible.
Interpretation of visual fields with special reference to octopusHaitham Al Mahrouqi
The document provides an overview of visual field interpretation using the Octopus perimeter. It discusses what a visual field is, why they are important, and types of perimetry including static and kinetic. It describes advantages of different test strategies like TOP and SITA fast that can reduce test time. Key aspects of the Octopus 7-in-1 printout are outlined including demographic data, reliability indices, threshold values compared to norms, and mean deviation and pattern deviation plots.
This document discusses esotropia, or convergent strabismus. It describes the different types of esotropia including concomitant and incomitant deviations. It further categorizes esotropia as accommodative or non-accommodative. Early-onset esotropia developing within the first 6 months is discussed in detail, including typical clinical features and management with early surgical alignment and treatment of amblyopia and refractive error. Subsequent development of inferior oblique overaction and dissociated vertical deviation are also addressed.
This document discusses the application of anterior segment optical coherence tomography (AS-OCT) in diagnosing various ocular conditions. It provides an overview of AS-OCT imaging principles and compares it to ultrasound biomicroscopy. The document then examines the use of AS-OCT in diagnosing and monitoring conditions of the cornea, conjunctiva, and anterior chamber angle/glaucoma. Examples of pathologies that can be identified include corneal scars, Fuchs' dystrophy, graft rejection, angle closure, and bleb assessment after glaucoma surgery.
This document discusses the diagnosis of pre-perimetric glaucoma. It begins by defining pre-perimetric glaucoma as optic nerve abnormalities seen on structural tests with normal visual fields. It then discusses the need for early diagnosis before functional changes occur. Various functional tests are described like standard automated perimetry, short wavelength automated perimetry, frequency doubling technology, and others. Structural tests like confocal scanning laser ophthalmoscopy, optical coherence tomography, and their principles are summarized.
The document discusses corneal tomography parameters and their significance in evaluating post-refractive surgery eyes and detecting ectatic disorders. It provides normal values and characteristics for pachymetry, keratometry, sagittal and elevation maps, and other Pentacam parameters. Abnormal findings that may indicate conditions like keratoconus and pellucid marginal degeneration are also described.
This document discusses the anatomy and development of the vitreous humor in the eye. It begins by describing the embryological origin of vitreous cells from surface ectoderm, neuroectoderm, and mesodermal tissues. During the primary vitreous stage, the vitreous body begins forming before closure of the choroidal fissure and appears as a fibrillated secretion filling the vitreous space. The document then covers the general features, structure including hyaloid layers, cortical and medullary regions, attachments, composition and transport processes of the mature vitreous humor. It concludes by describing the physicochemical properties and factors affecting expansion and contraction of the vitreous gel.
UBM and ASOCT provide high-resolution cross-sectional images of the anterior segment including the cornea, anterior chamber, angle, and iris. ASOCT uses optical coherence tomography with a wavelength of 1310nm for improved penetration and reduced retinal damage compared to posterior segment OCT. It allows high-speed imaging of dynamic structures. ASOCT has applications in assessing corneal diseases and procedures, glaucoma (including angle anatomy and iridotomy evaluation), and intraocular lens implantation. Measurements of angle width parameters help evaluate angle closure risk. While valuable for objective angle assessment, ASOCT cannot image all anatomical structures involved in glaucoma.
2. Analisi cornea con Casia2
• L'ultima presentazione
l'abbiamo chiusa con il
report Pre-Cataratta.
• La finestra Pre-cataratta dà
tutti i parametri necessari ad
uno sguardo veloce.
• Soffermiamoci sui parametri
più significativi
3. Valori biometrici
1. Analisi cheratometrica
2. Parametri refrattivi per la
scelta della IOL
3. Parametri biometrici
della camera anteriore
321
4. Considerazioni prima della
• FRCyl Fourier real cylinder. Astigmatismo totale
aberrometrico, importante nella decisione per una lente
torica.
• ECC Eccentricity corneal index. Un valore positivo indica
una cornea prolata, un valore negativo indica una cornea
oblata.
• HOAs High Order Aberr. Un valore alto è da tenere in
considerazione per l'eventuale impianto di una lente
multifocale. Il valore alto può inficiare la qualità visiva.
• SA Spherical Aberration. Il valore medio misurato di una
cornea che non ha subito chirurgie è di 0,27 µm. La scelta
della IOL deve tenere in considerazione il valore SA, nella
scelta della IOL il valore totale SA deve poter essere il più
possibile basso. Con SA alto la scelta della IOL dovrebbe
ricadere su una lente ad aberrazione sferica negativa. Un
valore più basso della media potrebbe far scegliere una
IOL con aberr. sferica neutra. La scelta è orientata ad una
qualità della visione.
IOL Choice
5. Cosa ci può dare una topografia OCT
• Come per tutti gli strumenti
che analizzano la curvatura
anteriore e posteriore si
possono avere queste mappe:
• Assiale
• Tangenziale
• Pachimetria
• Elevazione
• ACD
6. Qual'è la differenza?
• La differenza è nell' Axial Power (Keratometric) map.
• Da non confondere con l' Axial anterior map.
• L'Axial ant. Power map (Casia2) è la misurazione diretta della
curvatura assiale della superficie ant corneale, senza nessun rapporto
medio con la curvatura posteriore. (Keratometric index 1.376)
Topografi convenzionali hanno sempre dato la curvatura anteriore,
tenendo in considerazione le informazioni stimate della curvatura
posteriore, in modo da calcolare le IOL considerando il potere refrattivo
corneale.
• Con il Casia2 la curvatura posteriore viene misurata direttamente
• L' Axial Power [Keratometric] è la mappa assiale ricorretta tenendo
conto del rapporto della curvatura assiale posteriore. (Keratometric index
1.3375) (Topografia convenzionale)
• Il Casia2 ci dà quindi 4 mappe assiali: Axial power keratometric, Axial
power anterior, Axial power posterior, Axial power real.
• Le costanti per il calcolo delle IOL sono fatte con la curvatura Axial
Power Keratometric.
7. Analisi aberrometrica
della cornea con Casia2
• La rappresentazione aberrometrica può essere fatta
sulla base di più modelli
• I modelli di rappresentazione vengono sviluppati per
semplificare la lettura di funzioni o segnali
complicati (come l'aberrometria ottica)
• Nelle prossime slides diamo le informazioni di base
su come il Casia2 rappresenta l'aberrometria
corneale, ma non temete, nell'ultima slide ci sarà
l'applicazione pratica
8. Fourier e
Casia2
• Cosa c'entra il Casia2 con Fourier?
• In analisi matematica, l'analisi di Fourier, nota anche
come analisi armonica, è una branca di ricerca che ha
preso avvio dalle ricerche di Jean Baptiste Joseph
Fourier che, nei primi anni dell'Ottocento, riuscì a
dimostrare matematicamente come una
qualunque funzione periodica poteva essere scomposta
in una somma di infinite "opportune" funzioni o
componenti sinusoidali (seno e coseno) dette armoniche.
Da tale constatazione nasce dunque l'idea di scomporre
funzioni complicate in una serie di funzioni, nota
come serie di Fourier, rendendone l'analisi più semplice e
vantaggiosa. Dal concetto matematico di serie di Fourier
discende anche la nozione di trasformata di Fourier ed il
relativo concetto associato di dominio della
frequenzadominio della frequenza
E' l'idea di scomporre
funzioni complicate in una
serie di funzioni più
semplici
Il numero delle
componenti semplici sarà
maggiore quanto più fine
sarà la campionatura
Il Casia2 utilizza le 4 funzioni
semplici più incidenti rispetto
a una campionatura più
amplia e complessa come il
polinomio di Zernike
10. Aberrazioni più utili:
Eliminiamo tutte
quelle aberrazioni
meno incidenti, che
possono creare
confusione,
raggruppandole come
HOA (Aberrazioni di
alto ordine)
11. Fourier applicato alla topografia
• Questi grafici esprimono le componenti "armoniche"
dell'analisi di Fourier.
• La somma delle varie "armoniche/componenti" dà il
risultato totale
• Spherical eq. È la componente refrattiva di base
• Asymmetry è la prima "armonica" che dà la componente
differenziale tra emisferi (180°)
• Regular astigmatism dà l'armonica per l'astigmatismo
reale (90°)
• Higher order sono tutte le restanti componenti di altro
ordine (rumore)
12. Analisi di Fourier al posto dello Zernike
• I colori della mappa Spherical eq.
evidenziano eventuali aberrazioni
sferiche
• Reguar astigmatism evidenzia il
cilindro puro al netto dalla base sferica
• Asymmetry evidenzia eventuali Coma
• HOA raggruppa tutte le aberrazioni di
alto ordine ed evidenzia molto bene
eventuali aberrazioni Trifoglio o
Quadrifoglio
13. Cheratocono screening
• Come screening del Cheratocono il
Casia2 ha la possibilità di essere il più
fine tomografo sul mercato.
• "Customizzare" ogni tipo di esame
ci permette di poter eseguire una
topografia corneale composta da 128
B-scan (la più dettagliata presente sul
mercato)
• Una precisione di 2,8° (una B-scan
ogni 2,8°) evidenzia ogni minimo
cambio di curvature specialmente
nella parete posteriore della cornea
15. Ectasia screening
• ESI Ectasia Screening Index è un
parametro che analizza sia la
curvatura ant che post della
cornea.
• Utile anche per un eventuale
valutazione pre chirurgia
refrattiva.
• Nella slide successiva vediamo
un applicazione pratica sulla
sensibilità dello screening...
16. Trend analisi per il
cheratocono
• Analisi e comparazione delle
mappe nel tempo per capire
l'eventuale evoluzione del
cheratocono
17. Caso clinico 1
• Trattamenti refrattivo
ipermetropico decentrato.
• ESI anteriore 7% di similarità
per l'anomalia del
decentramento.
• La parete posteriore della
cornea non evidenzia nulla di
anomalo.
18. Caso clinico 2
• ESI posteriore anomalo con
indice al 37%.
• Nella assiale posteriore e
nella tangenziale posteriore ci
sono 2 cambi di curvatura
notevoli
19. Caso clinico 2
• Anche l'analisi di Fourier ci dà
delle informazioni importanti.
• Anteriormente nella mappa
completa si nota un cilindro
assimmetrico, come viene
evidenziato nella sola
componente/armonica di
assimmetria (asymmetry map).
• E' sempre consigliabile
confrontare lo screening con un
quadro più completo
topografico/aberrometrico
20. Caso clinico 2
• L'anomalia della curvature
posteriore è data da un tunnel
corneale troppo lungo che và
ad inerferire con una parte
centrale di cornea.
• Per il software non è
possibile distingurne il motivo
ma è sicuramente un anomalia
da segnalare!
23. OCT Vs Scheimpflug
• Il Casia2 passa attraverso le
opacità corneali garantendo una
ottima precisione di misura nei
tessuti oltre l'opacità.
• Questa precisione non avviene
con una Scheipflug camera in
quanto la luce non passa
attraverso l'opacità in cornea.
Tutte le informazioni dopo
l'opacità sono mancanti o poco
attendibili.
24. OCT Vs Scheimpflug
• Con il Casia2 riusciamo ad andare altre
le semplici opacità corneali
25. In conclusione
Con il Casia2 la topografia rappresenta la
migliore soluzione per studiare la curvatura
corneale in qualsiasi situazione.
La scelta di analizzare la superficie anteriore
o posteriore corneale unita alla
raffiguarazione dell'insieme (mappa reale)
ci dà idea delle varie influenze refrattive.
Lo studio aberrometrico scomposto in
armoniche (Fourier) semplifica molto la
comprensione rispetto ad un scomposizione
più complessa come Zernike. Le aberrazioni
più influenti vengono evidenziate mentre
tutte le altre aberrazioni di alto ordine che
creano (rumore) vengono espresse con un
unico valore.
Tutti i valori (cheratometrici, aberrometrici)
vengono indicati con un codice colore a
seconda degli indici di normalità.
To be continued