Ophthalmology: Strabismus and Amblyopia Diagnosis
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Questions and Answers

What is the minimum improvement in visual acuity required for a patient to be considered improved in the ATS1 study?

  • 5 lines improvement
  • 1 line improvement
  • 2 lines improvement
  • 3 lines improvement (correct)

    • What percentage of patients with moderate amblyopia improved by ≥ 3 lines in the ATS2b study?

  • 80%
  • 70%
  • 62% (correct)
  • 50%

    • What is the benefit of treating strabismus and amblyopia that refers to the ability to use both eyes together?

  • Binocular summation
  • Cosmesis
  • Increased binocular field
  • Stereopsis (correct)

    • What is the percentage of patients with bilateral amblyopia who achieved a visual acuity of ≥ 20/25 at 52 weeks in the ATS7 study?

    <p>74%</p> Signup and view all the answers

    What is the benefit of treating strabismus and amblyopia that refers to the ability to have a spare eye in case of vision loss in one eye?

    <p>Safety factor</p> Signup and view all the answers

    What is the percentage of patients with severe amblyopia who improved almost 5 lines in the ATS2a study?

    <p>Not specified</p> Signup and view all the answers

    What is the benefit of treating strabismus and amblyopia that refers to the improvement in visual acuity when using both eyes together?

    <p>Binocular summation</p> Signup and view all the answers

    What is the minimal deviation of the primary lines of sight required to diagnose strabismus?

    <p>1 prism diopter</p> Signup and view all the answers

    What is the percentage of patients with moderate amblyopia who improved to 20/30 or ≥ 3 lines in the ATS1 study?

    <p>More than 70%</p> Signup and view all the answers

    What is the best corrected visual acuity in an individual with amblyopia?

    <p>Worse than 20/20, not correctable by refractive means</p> Signup and view all the answers

    What is the component of normal binocular vision that is affected in patients with strabismus?

    <p>Motor component</p> Signup and view all the answers

    What is the percentage of patients who improved by ≥ 2 lines with optical correction alone in the ATS5 study?

    <p>77%</p> Signup and view all the answers

    Which of the following is NOT a component of normal binocular vision?

    <p>Cognitive area of the visual system</p> Signup and view all the answers

    What is the leading cause of monocular vision loss?

    <p>Not specified in the content</p> Signup and view all the answers

    What is the age limit for treating amblyopia?

    <p>There is no age limit for treating amblyopia</p> Signup and view all the answers

    What is the prevalence of amblyopia in the general population?

    <p>Not specified in the content</p> Signup and view all the answers

    What is the prevalence of strabismus in the general population?

    <p>Not specified in the content</p> Signup and view all the answers

    What is the definition of amblyopia according to the AAO?

    <p>Reduced visual acuity, not correctable by refractive means, and associated with form deprivation, strabismus, anisometropia, or other ambliogenic refractive errors</p> Signup and view all the answers

    What is the definition of strabismus?

    <p>A manifest deviation of the primary lines of sight of 1 prism diopter or more</p> Signup and view all the answers

    What is the relationship between strabismus and amblyopia?

    <p>Strabismus is a cause of amblyopia</p> Signup and view all the answers

    What is the prevalence of strabismus in children and teens according to global estimates?

    <p>0.13% to 4.7%</p> Signup and view all the answers

    Which of the following studies reported a prevalence of strabismus in Asian children as 0.80%?

    <p>STARS Study</p> Signup and view all the answers

    What is the most common cause of amblyopia?

    <p>Refractive error</p> Signup and view all the answers

    According to the Visual Acuity Impairment Study (1984), what is the leading cause of monocular vision loss in the 20-70+ age group?

    <p>Functional amblyopia</p> Signup and view all the answers

    What is the functional cure rate of amblyopia treatment according to Flax and Duckman (1978)?

    <p>76%</p> Signup and view all the answers

    What is the cosmetic cure rate of amblyopia treatment according to Flax and Duckman (1978)?

    <p>86%</p> Signup and view all the answers

    According to Kivlin and Flynn (1981), what percentage of amblyopic patients reach 20/40 or better?

    <p>60-85%</p> Signup and view all the answers

    Which of the following reviews found that age was not a significant factor in amblyopia treatment success?

    <p>Birnbaum et al (1977)</p> Signup and view all the answers

    What percentage of Hispanic/Latino children have strabismus according to the MEPEDS Study?

    <p>2.4%</p> Signup and view all the answers

    What is the prevalence of amblyopia in white children according to the BPEDS Study?

    <p>1.8%</p> Signup and view all the answers

    What is the sensitivity of parents in identifying strabismus in children?

    <p>65%</p> Signup and view all the answers

    What is the specificity of parents in identifying strabismus in children?

    <p>99%</p> Signup and view all the answers

    What is the prevalence of pseudo-esotropia in infants?

    <p>50%</p> Signup and view all the answers

    Why is the duration between onset and treatment critical in strabismus?

    <p>Because the longer the delay, the worse the prognosis</p> Signup and view all the answers

    What is the mode of transmission of strabismus?

    <p>Multifactorial</p> Signup and view all the answers

    What is the risk of strabismus in a sibling of a patient with strabismus?

    <p>High</p> Signup and view all the answers

    What is a risk factor for strabismus?

    <p>Hyperopia</p> Signup and view all the answers

    What is the importance of patient ocular history in strabismus diagnosis?

    <p>It is crucial</p> Signup and view all the answers

    What is the role of binocular vision in strabismus diagnosis?

    <p>It is essential</p> Signup and view all the answers

    What is an indication for recommending early examination of offspring or younger siblings?

    <p>Parent(s) have strabismus</p> Signup and view all the answers

    Which of the following is a risk factor for exotropia and esotropia?

    <p>All of the above</p> Signup and view all the answers

    What is the significance of discussing patient goals with respect to strabismus treatment?

    <p>To establish reasonable expectations and coincide with patient goals</p> Signup and view all the answers

    Which of the following neurologic conditions is associated with an increased risk of strabismus?

    <p>All of the above</p> Signup and view all the answers

    What is the primary difference between acquired and congenital strabismus?

    <p>Age of onset</p> Signup and view all the answers

    What is the significance of a family history of strabismus in a patient?

    <p>It increases the risk of strabismus in offspring</p> Signup and view all the answers

    How does age affect the prognosis of strabismus treatment?

    <p>The younger the patient, the better the treatment outcomes</p> Signup and view all the answers

    Which of the following is a risk factor for esotropia?

    <p>High maternal age at delivery</p> Signup and view all the answers

    What is the primary importance of obtaining a thorough patient ocular history in strabismus diagnosis?

    <p>To rule out underlying organic or congenital conditions</p> Signup and view all the answers

    What role does binocular vision play in strabismus diagnosis?

    <p>It is a key indicator of fusional vergence system function</p> Signup and view all the answers

    What is the significance of low vergence ability in parents with respect to strabismus?

    <p>It increases the risk of strabismus in offspring</p> Signup and view all the answers

    Which of the following is a common association with strabismus?

    <p>All of the above</p> Signup and view all the answers

    What is the estimated prevalence of strabismus in the general population?

    <p>1-2%</p> Signup and view all the answers

    What is the primary factor that influences the prevalence of strabismus in different populations?

    <p>Ethnicity</p> Signup and view all the answers

    What is the significance of a family history of hyperopia in parents with respect to strabismus?

    <p>It increases the risk of strabismus in offspring</p> Signup and view all the answers

    What is the primary reason for the high heritability of strabismus?

    <p>Genetic predisposition</p> Signup and view all the answers

    What is the primary consequence of untreated strabismus in children?

    <p>Development of amblyopia</p> Signup and view all the answers

    What is the primary goal of strabismus treatment in children?

    <p>To restore binocular vision and prevent amblyopia</p> Signup and view all the answers

    What is the primary difference between congenital and acquired strabismus in terms of age?

    <p>Congenital occurs before 1 year, acquired occurs after 1 year</p> Signup and view all the answers

    What is the significance of the age of onset in strabismus prognosis?

    <p>Intermittent onset is associated with a better prognosis</p> Signup and view all the answers

    What is the significance of a family history of strabismus in a patient's ocular history?

    <p>It is associated with a worse prognosis</p> Signup and view all the answers

    What is the role of binocular vision in strabismus diagnosis?

    <p>It is used to assess the severity of strabismus</p> Signup and view all the answers

    What is the prevalence of strabismus in the general population?

    <p>1-2%</p> Signup and view all the answers

    What is the significance of a sudden onset of strabismus?

    <p>It may signal a life-threatening situation</p> Signup and view all the answers

    What is the heritability of strabismus?

    <p>Both A and B</p> Signup and view all the answers

    What is the significance of the age of 2-4 months in congenital strabismus?

    <p>It is the age at which infants with constant, large-angle esotropia are unlikely to resolve spontaneously</p> Signup and view all the answers

    What is the characteristic of infants with esotropia according to the PEDIG study?

    <p>They have a range of characteristics, including constant, variable, and intermittent esotropia</p> Signup and view all the answers

    What is the primary reason for preferring the term 'infantile esotropia' over 'congenital esotropia'?

    <p>Because the term 'congenital' implies a present-at-birth condition, which is not always the case</p> Signup and view all the answers

    According to Sondi et al, what is the age threshold beyond which any exotropia is considered abnormal?

    <p>18 months</p> Signup and view all the answers

    What is the mode of genetic transmission of strabismus?

    <p>Multifactorial</p> Signup and view all the answers

    Which of the following is a critical component of a strabismus/amblyopia case history?

    <p>All of the above</p> Signup and view all the answers

    What is the most insidious type of onset in strabismus?

    <p>Insidious onset</p> Signup and view all the answers

    What is the primary reason for obtaining a thorough patient ocular history?

    <p>To understand the patient's concerns and expectations</p> Signup and view all the answers

    What is the role of binocular vision in strabismus diagnosis?

    <p>It is a primary diagnostic criterion</p> Signup and view all the answers

    What is the approximate prevalence of strabismus in the general population?

    <p>1-2%</p> Signup and view all the answers

    What is the primary reason for recommending early examinations for offspring or siblings of strabismics?

    <p>To detect strabismus at an early age</p> Signup and view all the answers

    What is the primary consideration when performing retinoscopy off axis?

    <p>Staying within 10 deg of visual axis to avoid significant errors</p> Signup and view all the answers

    What is the purpose of using keratometry in refractive error diagnosis?

    <p>To confirm astigmatic power and axis found by retinoscopy</p> Signup and view all the answers

    Which technique is used to control accommodation by patient during retinoscopy?

    <p>Using projected targets or cartoons</p> Signup and view all the answers

    What is the effect of increasing accommodation on refractive error measurement during retinoscopy?

    <p>It results in an artificial increase in negative refractive error or a decrease in positive refractive error</p> Signup and view all the answers

    What is the primary purpose of noncycloplegic static retinoscopy in refractive error diagnosis?

    <p>To screen for strabismic patients and consider out of phoropter refraction on children and all deviations &gt; 15∆</p> Signup and view all the answers

    What is the effect of retinal eccentricity on astigmatism?

    <p>Astigmatism increases progressively with retinal eccentricity</p> Signup and view all the answers

    What is the effect of accommodation on refractive error measurement during retinoscopy?

    <p>It results in an artificial increase in negative refractive error or a decrease in positive refractive error</p> Signup and view all the answers

    What is the purpose of using the near retinoscopy method (Mohindra) in refractive error diagnosis?

    <p>To measure refractive error at a working distance of 50cm in a dimly lit room</p> Signup and view all the answers

    What is the recommended dosage of Cyclopentolate for a 3-year-old?

    <p>1%</p> Signup and view all the answers

    What is the minimum amount of anisometropia associated with an increased risk of amblyopia?

    <p>1.00 D</p> Signup and view all the answers

    What is the relationship between astigmatism and retinal eccentricity?

    <p>Astigmatism increases with increasing retinal eccentricity</p> Signup and view all the answers

    What is the effect of staying within 10 deg of visual axis during retinoscopy?

    <p>It avoids significant errors in measuring astigmatic and spherical components</p> Signup and view all the answers

    When performing retinoscopy on a patient with strabismus, what factor do you need to control?

    <p>Axis of alignment</p> Signup and view all the answers

    What does scoping off-axis do to the refractive error?

    <p>Alters the axis of the refractive error</p> Signup and view all the answers

    How do you refract a constant esotropia on axis?

    <p>Using a phoropter</p> Signup and view all the answers

    What is the significance of refractive status in strabismus and amblyopia diagnosis?

    <p>It is a major etiological factor</p> Signup and view all the answers

    What percentage of children with strabismus have abnormal refractions?

    <p>72%</p> Signup and view all the answers

    What is the relationship between hyperopia and the development of esotropia?

    <p>Hyperopia is a risk factor for esotropia</p> Signup and view all the answers

    What is the recommended dosage of Cyclopentolate for an 8-month-old?

    <p>0.5%</p> Signup and view all the answers

    How do you determine if you have adequate cycloplegia?

    <p>By checking for 3 specific signs</p> Signup and view all the answers

    What is the primary limitation of Tropicamide in cycloplegic retinoscopy?

    <p>Poor at eliminating high accommodative tonus of childhood</p> Signup and view all the answers

    What is the recommended dosage of Cyclopentolate for children under 1 year of age?

    <p>0.5% solution, 2 drops, 1 drop wait 5 min, add 1 drop</p> Signup and view all the answers

    What is the effect of subtracting 1.25 D from the sphere value in children during Near Retinoscopy Method?

    <p>Underestimation of hyperopia</p> Signup and view all the answers

    What is the correlation between Near Retinoscopy Method and cycloplegic methods?

    <p>About 35% of the time</p> Signup and view all the answers

    What is the alternative to using drops in Cyclopentolate administration?

    <p>Spray application</p> Signup and view all the answers

    What is the significance of neutralizing primary meridians in Near Retinoscopy Method?

    <p>To improve accuracy of refractive error</p> Signup and view all the answers

    What is the recommended adjustment for children over 2 years of age during Near Retinoscopy Method?

    <p>Subtract 1.00 D from the sphere value</p> Signup and view all the answers

    What is the purpose of occluding one eye during Near Retinoscopy Method?

    <p>To improve accuracy of refractive error</p> Signup and view all the answers

    What is the benefit of using Near Retinoscopy Method as a supplemental method?

    <p>It can be used in conjunction with cycloplegic retinoscopy</p> Signup and view all the answers

    What is the significance of considering the scoping 'on axis' in Near Retinoscopy Method?

    <p>To ensure proper alignment of the retinoscope</p> Signup and view all the answers

    What is the maximum duration of cycloplegia induced by atropine?

    <p>10-18 days</p> Signup and view all the answers

    What is the recommended dosage of atropine for patients under 1 year of age?

    <p>0.5% ung/soln BID x 3 days prior to exam</p> Signup and view all the answers

    What is a symptom of atropine toxicity?

    <p>All of the above</p> Signup and view all the answers

    What is the maximum duration of mydriasis induced by atropine?

    <p>As long as 12 days</p> Signup and view all the answers

    What is the time frame for maximum cycloplegia to occur when using atropine?

    <p>3-6 hours</p> Signup and view all the answers

    What is a common combination used to decrease stinging with topical anesthetics?

    <p>Lidocaine and tetracaine</p> Signup and view all the answers

    When is cycloplegia maximum when using atropine in patients over 1 year of age?

    <p>Within 3-6 hours</p> Signup and view all the answers

    What is the recommended dosage of atropine for patients over 1 year of age?

    <p>1.0% ung/soln BID x 3 days prior to exam</p> Signup and view all the answers

    What is a symptom of toxicity when using a particular cycloplegic agent?

    <p>Dryness of skin and mouth</p> Signup and view all the answers

    What is the time frame for mydriasis to occur when using atropine?

    <p>Within 30-60 min</p> Signup and view all the answers

    What is the primary characteristic of amblyopia?

    <p>Unilateral or infrequent bilateral condition with best-corrected visual acuity poorer than 20/20</p> Signup and view all the answers

    How do amblyopes typically respond during visual acuity testing?

    <p>With slow and irregular responses, even for letters above their acuity threshold</p> Signup and view all the answers

    What is a limitation of the Snellen chart in assessing patients with amblyopia?

    <p>It does not account for crowding</p> Signup and view all the answers

    What is the primary advantage of the Psychometric Visual Acuity method over the Snellen chart?

    <p>It takes into account crowding and other context-specific factors</p> Signup and view all the answers

    When is the Psychometric Visual Acuity method preferred over the Snellen chart?

    <p>When assessing patients with amblyopia</p> Signup and view all the answers

    How is monocular visual acuity typically assessed in patients with latent nystagmus?

    <p>With occlusion of the opposite eye</p> Signup and view all the answers

    What is the primary use of interferometry in visual acuity assessment?

    <p>To assess visual acuity in infants</p> Signup and view all the answers

    Does interferometry tend to over-estimate or under-estimate visual acuity?

    <p>Over-estimate</p> Signup and view all the answers

    What is a key consideration when assessing visual acuity in patients with amblyopia?

    <p>Accounting for crowding and context-specific factors</p> Signup and view all the answers

    Why is it important to accurately diagnose amblyopia?

    <p>Because incorrectly diagnosing amblyopia can have serious consequences</p> Signup and view all the answers

    What is the characteristic contrast sensitivity loss in anisometropic amblyopia?

    <p>Across all spatial frequencies</p> Signup and view all the answers

    What is the purpose of Grating Acuity Assessment using an Interferometer?

    <p>To determine the VA prognosis for amblyopes</p> Signup and view all the answers

    What is the benefit of using a pinhole VA in visual acuity testing?

    <p>To rule out uncorrected refractive error, corneal distortion and ocular media abnormalities</p> Signup and view all the answers

    What is the limitation of the Snellen full chart in visual acuity testing?

    <p>It only measures high contrast visual acuity</p> Signup and view all the answers

    What is the purpose of the Psychometric VA method in visual acuity testing?

    <p>To determine a reliable baseline VA</p> Signup and view all the answers

    What is the significance of the Interferometer Study by Selenow (1986) in visual acuity testing?

    <p>It found that pre-therapy laser VA is highly correlated with post-therapy Snellen/S-Chart VA</p> Signup and view all the answers

    What is the benefit of contrast sensitivity testing in visual acuity assessment?

    <p>It provides a broader picture of the loss of resolution</p> Signup and view all the answers

    What is the purpose of using a high plus lens or translucent occluder in visual acuity testing?

    <p>To blur the eye not being tested</p> Signup and view all the answers

    What is the significance of the overall strategy in visual acuity testing?

    <p>It provides a step-by-step approach to visual acuity assessment</p> Signup and view all the answers

    What is the purpose of monocular visual acuity assessment?

    <p>To assess visual acuity in one eye</p> Signup and view all the answers

    What is the primary advantage of the S-Chart Psychometric Visual Acuity Test over the Snellen chart?

    <p>It provides a more standardized difficulty of letters and contour interaction effect.</p> Signup and view all the answers

    Which of the following is a feature of the Psychometric Visual Acuity Cards (PVA Cards)?

    <p>They consist of Tumbling E's with contour interaction bars.</p> Signup and view all the answers

    What is the primary purpose of the multiple pinhole method in visual acuity testing?

    <p>To rule out uncorrected refractive error or refracting surface problems.</p> Signup and view all the answers

    What is the primary limitation of the Snellen chart in terms of visual acuity testing?

    <p>It is limited to evaluating high spatial frequencies.</p> Signup and view all the answers

    What is the primary advantage of the Contrast Sensitivity Function (Vis-Tech System) over traditional visual acuity tests?

    <p>It allows assessment of visual resolution over a broad range of spatial frequencies.</p> Signup and view all the answers

    What is the primary difference between the S-Chart Psychometric Visual Acuity Test and the Psychometric Visual Acuity Cards (PVA Cards)?

    <p>The S-Chart uses a projected chart, while the PVA Cards use a handheld card.</p> Signup and view all the answers

    What is the primary advantage of the psychometric visual acuity method over traditional visual acuity tests?

    <p>It provides a more standardized difficulty of letters and contour interaction effect.</p> Signup and view all the answers

    What is the primary purpose of monocular visual acuity assessment?

    <p>To identify patients with uncorrected refractive error or refracting surface problems.</p> Signup and view all the answers

    What is the primary limitation of the Snellen chart in terms of visual acuity testing in patients with amblyopia?

    <p>It is not effective in patients with amblyopia.</p> Signup and view all the answers

    What is the primary advantage of the S-Chart Psychometric Visual Acuity Test over the Snellen chart in patients with amblyopia?

    <p>It provides a more standardized difficulty of letters and contour interaction effect.</p> Signup and view all the answers

    What is the primary limitation of the Snellen chart in assessing visual acuity in amblyopic patients?

    <p>Assigning visual acuity based on an arbitrary number of letters missed</p> Signup and view all the answers

    Which of the following is a cause of amblyopic 'behavior' during visual acuity testing?

    <p>All of the above</p> Signup and view all the answers

    What is the advantage of using isolated letters in visual acuity testing?

    <p>Letters are less affected by contour interaction effects</p> Signup and view all the answers

    What is the primary difference between the standard Snellen chart and the psychometric visual acuity method?

    <p>The method of assigning visual acuity</p> Signup and view all the answers

    What is the significance of assessing monocular visual acuity in amblyopic patients?

    <p>To determine the effectiveness of treatment</p> Signup and view all the answers

    Which of the following is a limitation of the Snellen chart in assessing visual acuity?

    <p>All of the above</p> Signup and view all the answers

    What is the primary advantage of using the psychometric visual acuity method over the standard Snellen chart?

    <p>More accurate measurement of visual acuity</p> Signup and view all the answers

    Which of the following is a cause of reduced contrast sensitivity function in amblyopic patients?

    <p>Abnormal spatial distortions and uncertainty</p> Signup and view all the answers

    What is the significance of assessing visual acuity with a single line versus a full chart?

    <p>To determine the effectiveness of treatment</p> Signup and view all the answers

    Which of the following is a limitation of the Snellen chart in assessing visual acuity in amblyopic patients?

    <p>All of the above</p> Signup and view all the answers

    What type of functional amblyopia is caused by physical obstruction along the line of sight, which prevents the formation of a well-focused, high contrast image on the retina?

    <p>Form Vision Deprivation Amblyopia</p> Signup and view all the answers

    What is the main difference between functional amblyopia and organic vision loss?

    <p>Functional amblyopia is recoverable with treatment, while organic vision loss is not.</p> Signup and view all the answers

    Which type of amblyopia is associated with a significant difference in refractive error between the two eyes?

    <p>Anisometropic amblyopia</p> Signup and view all the answers

    What is the term for the partial or complete loss of binocular vision due to a defect in the visual pathway?

    <p>Binocular vision anomaly</p> Signup and view all the answers

    What is the typical visual acuity loss seen in Form Vision Deprivation Amblyopia?

    <p>&gt;20/200</p> Signup and view all the answers

    What is the term for the difference in refractive error between the two eyes that can lead to amblyopia?

    <p>Anisometropia</p> Signup and view all the answers

    What is the percentage of the general population affected by Form Vision Deprivation Amblyopia?

    <p>0.1-1%</p> Signup and view all the answers

    What percentage of strabismic amblyopes are amblyopic?

    <p>14%</p> Signup and view all the answers

    What is the mean VA of strabismic amblyopes?

    <p>20/70</p> Signup and view all the answers

    What is the prevalence of amblyopia in individuals with strabismus?

    <p>1/3</p> Signup and view all the answers

    What is the amblyogenic mechanism in strabismic amblyopia?

    <p>All of the above</p> Signup and view all the answers

    What is the relationship between depth of amblyopia and size of strabismus?

    <p>No relationship</p> Signup and view all the answers

    What is the type of amblyopia that occurs when the components of the visual pathway fail to develop?

    <p>Organic vision loss</p> Signup and view all the answers

    What is the feature of strabismic amblyopes' visual abnormalities?

    <p>Spatial distortion and uncertainty in the central field</p> Signup and view all the answers

    What is a crucial aspect to consider when dealing with an amblyopic eye in the presence of an organic abnormality?

    <p>Ensuring the organic abnormality unequivocally accounts for the vision loss before dismissing rehabilitation</p> Signup and view all the answers

    Which of the following diagnostic tests would show a normal result in functional amblyopia?

    <p>Pupils</p> Signup and view all the answers

    What happens to the visual acuity when a neutral density filter is used in an eye with functional amblyopia?

    <p>It stays about the same</p> Signup and view all the answers

    What is the primary difference between the outcome of the neutral density filter test in normal eyes and those with functional amblyopia?

    <p>Normal eyes show a moderate decrease in VA, while amblyopic eyes show little to no change</p> Signup and view all the answers

    What is the primary cause of Isoametropic Amblyopia?

    <p>High but equal refractive errors</p> Signup and view all the answers

    What would be the expected outcome of the neutral density filter test in an eye with organic pathology?

    <p>A drastic decrease in VA</p> Signup and view all the answers

    What is the primary cause of Gradually progressive and painless loss of central vision?

    <p>Lack of B vitamins</p> Signup and view all the answers

    Why is it essential to consider the possibility of coincidental organic abnormalities when dealing with functional amblyopia?

    <p>To ensure accurate diagnosis and treatment planning</p> Signup and view all the answers

    What is the minimum difference in refractive error required to diagnose Anisometropia?

    <p>1 D</p> Signup and view all the answers

    What is the primary goal when dealing with an amblyopic eye in the presence of an organic abnormality?

    <p>To determine the relationship between the organic abnormality and the vision loss</p> Signup and view all the answers

    Which of the following is not a characteristic of Psychogenic or hysterical vision loss?

    <p>Strabismus</p> Signup and view all the answers

    What is the refractive error associated with Astigmatism that can lead to Amblyopia?

    <p>&gt;2.50 D</p> Signup and view all the answers

    What is the primary difference between Psychogenic amblyopia and Relative amblyopia?

    <p>Origin of vision loss</p> Signup and view all the answers

    What is the significance of the neutral density filter test in diagnosing functional amblyopia?

    <p>It distinguishes between functional amblyopia and organic pathology</p> Signup and view all the answers

    What is the relationship between Strabismus and Amblyopia?

    <p>Strabismus is a cause of Amblyopia</p> Signup and view all the answers

    What is the expected outcome of the Amsler grid test in functional amblyopia?

    <p>Normal results</p> Signup and view all the answers

    Which of the following is a common associated condition with Refractive amblyopia?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic of corrected visual acuity in Isoametropic Amblyopia?

    <p>20/30 to 20/60</p> Signup and view all the answers

    What is the primary goal of treatment in Psychogenic amblyopia?

    <p>Reassurance and referral to a psychologist</p> Signup and view all the answers

    Why is it important to assess the relationship between the organic abnormality and the vision loss in an amblyopic eye?

    <p>To determine the feasibility of rehabilitation</p> Signup and view all the answers

    What is the prevalence of Anisometropic Amblyopia among all amblyopes?

    <p>1/3</p> Signup and view all the answers

    What is the association between Anisometropic Amblyopia and Strabismus?

    <p>1/3 of anisometropes have strabismus</p> Signup and view all the answers

    What is the characteristic refractive error in Psychogenic amblyopia?

    <p>Minor symmetric refractive error</p> Signup and view all the answers

    What is the primary feature of visual fields in Psychogenic amblyopia?

    <p>Tunnel-shaped fields</p> Signup and view all the answers

    What is the primary effect of form deprivation on the neurodevelopment of cortical mechanisms?

    <p>Impaired form and shape perception</p> Signup and view all the answers

    In anisometropic amblyopes, which of the following is a characteristic of the inhibitory effect?

    <p>It is more potent than the excitatory effect</p> Signup and view all the answers

    What is the primary difference between Amblyopia of Extinction and Amblyopia of Arrest?

    <p>Amblyopia of Extinction is caused by deterioration of central VA, while Amblyopia of Arrest is caused by conditions preventing visual development</p> Signup and view all the answers

    During which period of development is the visual system most fragile and requires clear retinal images to maintain normal levels of acuity and binocularity?

    <p>Sensitive Period</p> Signup and view all the answers

    What is the primary characteristic of binocular vision anomalies in strabismus?

    <p>Abnormal binocular interaction</p> Signup and view all the answers

    What is the primary effect of competitive suppression on visual acuity in amblyopia?

    <p>It reduces visual acuity</p> Signup and view all the answers

    What is the primary difference between the Critical Period and the Sensitive Period of visual development?

    <p>The Critical Period is when the visual system is developing, while the Sensitive Period is when the visual system is fragile</p> Signup and view all the answers

    In Visuoscopy, what is the purpose of using a low light level or green filter?

    <p>To reduce glare for the patient</p> Signup and view all the answers

    What is the significance of Haidinger's Brushes in binocular vision assessment?

    <p>They indicate the presence of eccentric fixation</p> Signup and view all the answers

    In Visuoscopy, what is the purpose of projecting a calibrated target on the retina?

    <p>To assess the localization of the fixation point</p> Signup and view all the answers

    What is the difference between eccentric fixation and eccentric viewing?

    <p>Eccentric fixation is a monocular phenomenon, while eccentric viewing is a binocular phenomenon</p> Signup and view all the answers

    What is the significance of the instruction 'Do you feel you are aiming your eye at the target' in Visuoscopy?

    <p>To assess the patient's localization ability</p> Signup and view all the answers

    What is the purpose of assessing the stability of eccentric fixation in Visuoscopy?

    <p>To identify fixation drifts and anomalies</p> Signup and view all the answers

    What is the importance of performing Visuoscopy in both eyes?

    <p>To detect any differences in fixation patterns between the two eyes</p> Signup and view all the answers

    What is the significance of the term 'parafoveolar' in the context of Visuoscopy?

    <p>It refers to a fixation point located 1-3 degrees off the fovea</p> Signup and view all the answers

    What is the purpose of using a calibrated target in Visuoscopy?

    <p>To project a standardized target on the retina for fixation assessment</p> Signup and view all the answers

    What is the significance of Fixation Disparity in binocular vision assessment?

    <p>It refers to a difference in fixation patterns between the two eyes</p> Signup and view all the answers

    What is the purpose of Retinomotor Value (RMV)?

    <p>To determine the angular distance from the fovea</p> Signup and view all the answers

    What is the characteristic of Eccentric Fixation (EF)?

    <p>The patient uses a part of the retina other than the fovea for fixation</p> Signup and view all the answers

    What is the significance of Principal Visual Direction (PVD)?

    <p>It is the direction in subjective space associated with a given retinal element</p> Signup and view all the answers

    What is the classification of Eccentric Fixation based on?

    <p>Localization, location, magnitude, and stability</p> Signup and view all the answers

    What is the difference between Foveal and Eccentric Fixation?

    <p>Foveal fixation uses the fovea for fixation, while eccentric fixation uses a part of the retina other than the fovea</p> Signup and view all the answers

    What is the incidence of Eccentric Fixation in Strabismus/Amblyopia?

    <p>60-80%</p> Signup and view all the answers

    What is the significance of Retinomotor Value in Binocular Vision?

    <p>It represents the angular distance and radial direction from the fovea</p> Signup and view all the answers

    What is the characteristic of Normal Fixation?

    <p>Fovea has a zero retinomotor value</p> Signup and view all the answers

    What is the purpose of understanding Eccentric Fixation in Strabismus/Amblyopia diagnosis?

    <p>To diagnose strabismus</p> Signup and view all the answers

    What is the significance of Principal Visual Direction in Binocular Vision?

    <p>It is the direction in subjective space associated with a given retinal element</p> Signup and view all the answers

    What is the primary difference between eccentric fixation and eccentric viewing?

    <p>Eccentric fixation is a pathological condition, while eccentric viewing is a normal phenomenon</p> Signup and view all the answers

    What is the significance of Haidinger's Brushes Test in amblyopia diagnosis?

    <p>It is used to estimate the amount of eccentric fixation</p> Signup and view all the answers

    What is the relationship between eccentric fixation and reduced visual acuity in amblyopia?

    <p>There is a direct correlation between the amount of eccentric fixation and the degree of reduced visual acuity</p> Signup and view all the answers

    What is the primary purpose of visuoscopy testing in amblyopia diagnosis?

    <p>To estimate the amount of eccentric fixation</p> Signup and view all the answers

    What is Schor's motor theory of eccentric fixation?

    <p>It explains that there is a larger incidence of eccentric fixation in strabismic amblyopia and that the direction of the eccentric fixation is typically in the direction of the strabismus</p> Signup and view all the answers

    What is the significance of eccentric fixation in strabismus diagnosis?

    <p>It contaminates the evaluation of the magnitude of deviation and angle of anomaly in strabismus</p> Signup and view all the answers

    What is the result of visuoscopy testing in a patient with a 2D nasal and 1D inferior eccentric fixation of the right eye and steady central fixation in the left eye?

    <p>The results will show a 2D nasal and 1D inferior eccentric fixation in the right eye and a central fixation in the left eye</p> Signup and view all the answers

    What is the significance of Brock-Givner After Image Transfer Test in amblyopia diagnosis?

    <p>It is used to estimate the amount of eccentric fixation</p> Signup and view all the answers

    What is the relationship between eccentric fixation and the angle of anomaly in strabismus?

    <p>Eccentric fixation contaminates the evaluation of the angle of anomaly</p> Signup and view all the answers

    What is the significance of eccentric fixation in amblyopia diagnosis?

    <p>It may mask or fool us when evaluating for strabismus</p> Signup and view all the answers

    What is the purpose of using a blue gelatin filter in the Macular Integrity Test (MIT)?

    <p>To enhance the visibility of the entopically perceived pattern of closely packed radiating lines.</p> Signup and view all the answers

    In the Brock-Givner After Image Transfer Test, what is the assumption underlying the test?

    <p>The patient has normal correspondence.</p> Signup and view all the answers

    What is the significance of the 'brush' effect in the Macular Integrity Test (MIT)?

    <p>It marks the position of the fovea.</p> Signup and view all the answers

    What is the purpose of determining the direction and magnitude of the eccentric fixation (EF) in the Macular Integrity Test (MIT)?

    <p>To assess the severity of binocular vision anomalies.</p> Signup and view all the answers

    What is the significance of the instruction to 'locate the brush in relationship to the fixation target' in the Macular Integrity Test (MIT)?

    <p>To determine the presence of eccentric fixation.</p> Signup and view all the answers

    What is the purpose of using a +10D lens in the Macular Integrity Test (MIT)?

    <p>To help patients who fail to see the brush.</p> Signup and view all the answers

    What is the significance of the Brock-Givner After Image Transfer Test in the diagnosis of amblyopia?

    <p>It is used to diagnose amblyopia in patients with normal correspondence.</p> Signup and view all the answers

    What is the purpose of occluding the normal eye in the Brock-Givner After Image Transfer Test?

    <p>To isolate the amblyopic eye's response to the afterimage.</p> Signup and view all the answers

    What is the significance of the 'flash vertical AI' in the Brock-Givner After Image Transfer Test?

    <p>It is used to create an afterimage on the fovea of the normal eye.</p> Signup and view all the answers

    What is the purpose of directing the patient to locate the afterimage in relation to the fixation mark in the Brock-Givner After Image Transfer Test?

    <p>To determine the direction and magnitude of the eccentric fixation.</p> Signup and view all the answers

    What is the primary characteristic of concomitant esotropia?

    <p>Constant deviation in all fields of gaze with either eye fixating</p> Signup and view all the answers

    What is the significance of cosmesis in strabismus evaluation?

    <p>It is a grading of the appearance of the eye Alignment</p> Signup and view all the answers

    What is the difference between primary and secondary vertical?

    <p>Primary vertical is a concomitant deviation, while secondary vertical is an incomitant deviation</p> Signup and view all the answers

    What would a patient with 20D esophoria report on UCT testing?

    <p>Esophoria at distance and orthophoria at near</p> Signup and view all the answers

    What is the significance of laterality in strabismus evaluation?

    <p>It indicates whether the deviation is unilateral or alternating</p> Signup and view all the answers

    What is the purpose of the 4DBO Test?

    <p>To evaluate binocular vision in patients with strabismus</p> Signup and view all the answers

    What would a patient with a right ex-cyclodeviation of 10° report on the double Maddox rod method?

    <p>A red line above the light</p> Signup and view all the answers

    What is the significance of the AC/A ratio in strabismus evaluation?

    <p>It measures the degree of accommodation-convergence relationship</p> Signup and view all the answers

    What is the purpose of direct observation in strabismus evaluation?

    <p>To assess the cosmesis of the patient</p> Signup and view all the answers

    What is the significance of concomitancy in strabismus evaluation?

    <p>It measures the degree of deviation in all fields of gaze with either eye fixating</p> Signup and view all the answers

    What is the primary diagnostic question when evaluating a suspected nonconcomitant deviation?

    <p>Is the deviation concomitant or nonconcomitant?</p> Signup and view all the answers

    What is the purpose of the three-step method circling technique for isolating the affected muscle?

    <p>To isolate individual muscle action</p> Signup and view all the answers

    Why is the red lens method not reliable in cases of heterophoria or intermittent strabismus?

    <p>Because the underacting eye’s image is not projected further into the affected field</p> Signup and view all the answers

    What is the Hess-Lancaster method used for?

    <p>To plot the deviation with the affected eye fixating</p> Signup and view all the answers

    What is the difference between anatomical, optical, and innervational causes of strabismus?

    <p>Anatomical causes refer to muscle imbalance, optical causes refer to refractive errors, and innervational causes refer to nerve damage</p> Signup and view all the answers

    What is the result of version testing if a patient has an LLR paresis?

    <p>The patient will have a limited version</p> Signup and view all the answers

    What is the difference between a primary and secondary deviation?

    <p>A primary deviation is present in the affected eye, while a secondary deviation is present in the normal eye</p> Signup and view all the answers

    What would you observe in right and left gaze during Hirschberg testing?

    <p>The patient’s eyes would be deviated</p> Signup and view all the answers

    What is a criteria for classifying the severity of nonconcomitancy?

    <p>The size of the deviation</p> Signup and view all the answers

    What is a characteristic of nonconcomitant deviations in strabismus?

    <p>They may represent a life-threatening situation.</p> Signup and view all the answers

    What is the primary reason for muscle underaction in strabismus?

    <p>All of the above.</p> Signup and view all the answers

    What is the angle between the lines of insertion and the visual axis for the rectus muscles?

    <p>23°</p> Signup and view all the answers

    How can you isolate the action of single muscles or yoked muscle pairs in strabismus diagnosis?

    <p>Position eyes so the visual axis and the lines of insertion are coincident.</p> Signup and view all the answers

    Which of the following is an anatomical cause of strabismus?

    <p>Faulty muscle insertion giving mechanical advantage.</p> Signup and view all the answers

    What is the primary reason for muscle overaction in strabismus?

    <p>Hering's law of equal innervation.</p> Signup and view all the answers

    What is the angle between the lines of insertion and the visual axis for the oblique muscles?

    <p>51°</p> Signup and view all the answers

    Which of the following is an innervational cause of strabismus?

    <p>Innervational deficiencies due to impairment of cranial nerves.</p> Signup and view all the answers

    What is the primary importance of obtaining a thorough patient ocular history in strabismus diagnosis?

    <p>To identify the underlying cause of the strabismus.</p> Signup and view all the answers

    What is the characteristic of concomitant strabismus?

    <p>Angle of deviation remains the same throughout all positions of gaze</p> Signup and view all the answers

    Which of the following is an anatomical cause of strabismus?

    <p>Abnormalities of EOM's</p> Signup and view all the answers

    What is the most common cause of strabismus in adults?

    <p>Head trauma</p> Signup and view all the answers

    What is the percentage of patients with acquired 3,4,6 nerve paresis who are older than 19?

    <p>90%</p> Signup and view all the answers

    What is the term for strabismus where the angle of deviation changes in different fields of gaze or with either eye fixating?

    <p>Nonconcomitant strabismus</p> Signup and view all the answers

    Which of the following is an optical cause of strabismus?

    <p>Refractive anisometropia</p> Signup and view all the answers

    What is the percentage of undetermined causes of strabismus?

    <p>26.2%</p> Signup and view all the answers

    What is the term for the deviation that may manifest if the magnitude of the deviation cannot be overcome by fusional vergence?

    <p>Manifest strabismus</p> Signup and view all the answers

    What is the characteristic of most nonconcomitant deviations?

    <p>Nuclear or infranuclear origin</p> Signup and view all the answers

    What is the primary purpose of the Red Lens Test in version testing?

    <p>To confirm the findings of an uniocular anomaly during version testing</p> Signup and view all the answers

    What is the main difference between concomitant and nonconcomitant strabismus?

    <p>The presence or absence of restriction in ocular movements</p> Signup and view all the answers

    Which of the following methods is used to assess concomitancy?

    <p>Red Lens Test</p> Signup and view all the answers

    What is the primary purpose of the three-step method?

    <p>To isolate the affected muscle in duction testing</p> Signup and view all the answers

    What is the Hess-Lancaster method used for?

    <p>To plot the fields of action of the extraocular muscles</p> Signup and view all the answers

    What is the primary difference between anatomical and optical causes of strabismus?

    <p>The location of the defect in the eye</p> Signup and view all the answers

    What is the innervational cause of strabismus?

    <p>Abnormality in the nervous system controlling eye movements</p> Signup and view all the answers

    What is the primary purpose of duction testing?

    <p>To identify the affected muscle in strabismus</p> Signup and view all the answers

    What is the primary difference between concomitant and nonconcomitant strabismus in terms of treatment?

    <p>The presence or absence of restriction in ocular movements</p> Signup and view all the answers

    What is the primary purpose of Hering's Law of Equal Innervation?

    <p>To illustrate the equal innervation of contralateral synergists</p> Signup and view all the answers

    Which of the following cranial nerves innervates the Superior Oblique muscle?

    <p>CN4 (Trochlear)</p> Signup and view all the answers

    What is the primary indication of an abnormal head position in a patient with strabismus?

    <p>Ocular torticollis</p> Signup and view all the answers

    What is the purpose of the patch test in strabismus diagnosis?

    <p>To determine if the head tilt is due to ocular or skeletal problem</p> Signup and view all the answers

    What is the primary purpose of version testing in strabismus diagnosis?

    <p>To observe changes in eye position in each diagnostic action field</p> Signup and view all the answers

    What is the primary purpose of Sherrington's Law?

    <p>To illustrate the contraction of a muscle accompanied by relaxation of its antagonist</p> Signup and view all the answers

    Which of the following is a characteristic of concomitant strabismus?

    <p>The amount of deviation is the same in all directions of gaze</p> Signup and view all the answers

    What is the primary purpose of the three-step method for isolating the affected muscle?

    <p>To identify the affected muscle</p> Signup and view all the answers

    What is the primary difference between anatomical and optical causes of strabismus?

    <p>Anatomical causes are related to muscle imbalance, while optical causes are related to refractive errors</p> Signup and view all the answers

    Study Notes

    Strabismus and Amblyopia

    • Strabismus is a manifest deviation of the primary lines of sight of 1 prism diopter or more.
    • Amblyopia is a unilateral or infrequently bilateral condition with reduced visual acuity (poorer than 20/20) not correctable by refractive means, associated with form deprivation, strabismus, anisometropia, or other ambliogenic refractive errors.

    Epidemiology

    • Strabismus has a higher incidence in affected families (23-70%), and is the most common visual abnormality found in children aged 6-17, with a global prevalence of 0.13% to 4.7%.
    • Amblyopia has a prevalence of 0.2% to 6.2% in children and teens, with refractive errors being the most common cause.
    • Amblyopia causes more vision loss than trauma and other ocular diseases in the under-20 age group.

    Treatment Success

    • Functional cure vs Cosmetic cure: Flax & Duckman (1978) review found 76% functional cure rate and 86% cosmetic cure rate.
    • Kivlin & Flynn (1981) review found 60-85% of amblyopic patients reach 20/40 or better.
    • Birnbaum et al (1977) review found age is not a significant factor in success outcome.
    • Wick et al (1992) review found no age limit for treating amblyopia.
    • Pediatric Eye Disease Investigator Group (PEDIG 2002 to present) found improvement in moderate amblyopia in young children with patching or atropine.

    Benefits to the Patient

    • Single Vision
    • Cosmesis
    • Stereopsis
    • Increase in binocular field
    • Safety factor “spare eye”
    • Binocular summation (­ VA when binocular)
    • Improved kinesthetic cues
    • Reduced psychological impact

    Components of Normal Binocular Vision

    • Anatomical: Healthy sensory organs and visual pathways
    • Motor: Accurate monocular fixation of either eye, accurate bifoveal fixation
    • Perceptual: Not mentioned

    Patient Ocular History

    • Parent reports are not entirely reliable in identifying strabismus, with a sensitivity of 65% and specificity of 99% (Rosner & Rosner, 1988).
    • Infants may have a flat, wide bridge and epicanthal folds, which can confuse parents, leading to a high incidence of pseudo-esotropia (up to 50%).
    • Developmental periods of poor binocular coordination may also confuse parents, and photographs can be helpful in identifying strabismus.

    Patient Medical History

    • The duration between the onset of strabismus and treatment is critical, especially when the onset is early.
    • The patient's medical history should include information about previous treatments, such as occlusion, and the final results.

    Family Ocular History

    • The prevalence of family ocular history (FOHx) of strabismus/amblyopia is high in siblings presenting with strabismus.
    • The transmission of strabismus is likely multifactorial, with factors including high AC/A ratio, hyperopia (>1.50D), eso/exophoric tendency, and poor vergence ability.
    • Certain situations prompt the recommendation of early examinations for offspring or younger siblings, such as:
      • Parents or older siblings having strabismus.
      • Parents and siblings being normal, but having a FOHx of strabismus.
      • Parents being normal, but having low vergence ability and significant hyperopia (>1.50D).

    Risk Factors for Strabismus

    • Low birth weight, maternal cigarette smoking, and increasing maternal age are associated with an increased risk of strabismus (Chew et al, 1994).
    • Neurologic abnormalities, seizure states, central nervous system, and skeletal conditions are also associated with an increased risk of strabismus.

    Strabismus and Diplopia

    • The patient's symptoms, such as diplopia, can be affected by various factors, including the position of the images, head movements, and distance.
    • The patient's general health should also be considered when assessing strabismus and diplopia.

    Strabismus without Symptoms

    • Patients with long-standing strabismus may have sensory adaptations, such as suppression or anomalous correspondence.
    • These patients may not recognize symptoms associated with their vision.

    Reduced Visual Acuity

    • Functional amblyopia is generally monocular, associated with early form deprivation, uncorrected refractive error, strabismus, or a combination.
    • It is essential to rule out congenital or pathological causes of reduced visual acuity.

    Time and Type of Onset

    • Congenital (infantile) strabismus is critical in determining prognosis.
    • Congenital esotropia is not present at birth but develops between 2 and 4 months (Archer et al, 1989).
    • Acquired strabismus can be divided into early acquired (< 5 years old) and late acquired (> 5 years old).
    • Sudden onset of strabismus can be due to trauma or may signal a life-threatening situation.

    Diagnosis - Case History

    • The 7 components of a strabismus/amblyopia case history are:
      • Chief Complaint (CC)
      • Signs and Symptoms (S/S)
      • Onset
      • Patient Ocular History (POHx)
      • Patient Medical History (PMHx)
      • Family Ocular History (FOHx)
      • Goals

    Introduction to Strabismus/Amblyopia Diagnosis

    • Refractive status is an important etiological factor in strabismus and amblyopia.
    • 1/3 of all comitant ET's resolved by corrective lenses.
    • ~50% of all amblyopia caused by anisometropia.
    • 72% of children with strabismus had abnormal refractions.

    Refractive Status and Future Development of ET and Amblyopia

    • > 2.00 D Hyperopia associated with future development of ET and amblyopia.
    • > 1.00 D Anisometropia, any meridian associated with future development of ET and amblyopia.
    • > +2.50 D at 1 year = 20x more likely to develop strabismus than emmetropic children.
    • > +3.50 D at 6-8 months = 13x more likely to develop strabismus and 6x more likely to become amblyopic by age 4.

    Scoping off Axis

    • Astigmatism increases progressively with retinal eccentricity and is nearly independent of central refraction.
    • Spherical component decreases as a function of retinal eccentricity.
    • Stay within 10 deg (~17Δ) of visual axis to avoid significant errors both in astigmatic and spherical components.

    Controlling Accommodation

    • Increased accommodation by patient results in artificial increase in (-) or decrease in (+).
    • Look for abnormally small pupils or decreasing pupil size beyond normal miosis from light during retinoscopy.
    • Try to control accommodation by using projected targets or cartoons.

    Keratometry

    • Use to confirm astigmatic power and axis found by retinoscopy.

    Noncycloplegic Static Retinoscopy

    • Initial screening procedure.
    • Scoping strabismic patients.
    • Hold correcting prism in front of fixating eye for ET's and verticals.
    • Align Purkinje's images or use corrective prism BI for XT's.

    Near Retinoscopy Method (Mohindra)

    • Patient sits in chair or on parents lap at 50cm working distance.
    • Room lights out, patient fixates retinoscope, monitor corneal reflex to make sure scoping "on axis".
    • One eye occluded, neutralize primary meridians, subtract 1.25 D from the sphere value.
    • Correlation with cycloplegic methods about 35% of the time.

    Cycloplegic Retinoscopy

    • Cyclopentolate recommended dosage:
      • < 1 year of age, 0.5% soln. 2gtts (1gtt wait 5 min, add 1 gtt).
      • > 1 year of age, 1.0% soln. 2gtts (1gtt wait 5 min, add 1 gtt).
    • Cycloplegic refraction:
      • Mydriasis within 30-60 min.
      • Cycloplegia max in 30-45 min.
      • Duration: mydriasis ~ 24 hours, cycloplegia 8-24 hours.
    • Toxicity symptoms: restlessness, aimless wandering, irrelevant talking, hallucinations, memory loss, faulty orientation to time/place.

    Atropine

    • Recommended dosage:
      • < 1 year of age, 0.5% ung/soln BID x 3 days prior to exam.
      • > 1 year of age, 1.0% ung/soln BID x 3 days prior to exam.
    • Response:
      • Mydriasis within 30-45 min.
      • Cycloplegia within 30-50 min, max in 3-6 hours.
    • Duration:
      • Mydriasis as long as 12 days.
      • Cycloplegia 10-18 days.
    • Toxicity symptoms: dryness of skin and mouth, flushing of face, fever, tachycardia, irritability or delirium.

    Amblyopia Definition and Clinical Guidelines

    • Amblyopia is a unilateral (or infrequently bilateral) condition where the best-corrected visual acuity is poorer than 20/20 in the absence of any structural or pathologic anomalies.
    • Occurs before 6 to 8 years of age with one or more of the following conditions: significant refractive error, constant unilateral strabismus, or form vision deprivation.

    Amblyopic Behavior during Visual Acuity Testing

    • Speed of response is slow and irregular, even for letters well above the patient's acuity threshold.
    • Letters are reported correctly and incorrectly on any given line over a large range of letter sizes.
    • Letters are occasionally read out of order and sometimes skipped.
    • VA obtained with isolated letters is better than single line or full chart.
    • Letters near the borders of the VA chart are frequently read more accurately than letters in the middle of the line.
    • Reliability of VA measurements obtained by repeated testing is poor.

    Causes of Amblyopic Behavior during VA Testing

    • Sensitivity to contour interaction effects.
    • Abnormal spatial distortions and uncertainty.
    • Reduced contrast sensitivity function.
    • Unsteady and inaccurate monocular foveal fixation.
    • Poor eye tracking ability.
    • Inaccurate accommodative response.

    Assessing Visual Acuity

    • Standard Snellen Chart:
      • Not designed to provide accurate and repeatable measurement of VA in amblyopic patients.
      • Faults: different number of calls per line, varying difficulty of letters, differing influences on visual resolution, few letter calls in lower acuity ranges, and arbitrary assignment of VA based on the number of letters missed.

    Psychometric Visual Acuity Method

    • Addresses the inadequacies of Snellen charts.
    • Provides an equal number of calls per acuity level.
    • Standardized difficulty of letters (Landolt C).
    • Standardized contour interaction effect.
    • 22 slide set evaluates acuity from 20/9 to 20/355.
    • Termination determined by psychophysical method.
    • Similar results to Snellen if VA better than 20/100, but S-Chart better if VA worse than 20/200.

    Other Assessment Methods

    • Grating Acuity Assessment (Interferometer, Retinometer):
      • Projects high-contrast interference fringes onto the retina.
      • Helps determine VA prognosis for amblyopes.
      • Tends to overestimate potential acuity.
    • Contrast Sensitivity Function (Vis-Tech System):
      • Assesses visual resolution over a broad range of spatial frequencies.
    • Multiple Pinhole:
      • Rules out uncorrected refractive error or refracting surface problems.

    Overall Strategy for Assessing Amblyopia

    • Snellen full chart to initially identify amblyopia presence.
    • Psychometric VA method to determine reliable baseline VA.
    • Pinhole VA to rule out uncorrected refractive error, corneal distortion, and ocular media abnormalities.
    • Contrast sensitivity testing to give a broader picture of the loss of resolution.
    • Interferometry to help establish a reasonable prognosis.

    Functional Amblyopia

    • Definition: Intact and normal visual pathway at birth, but fails to develop or operate normally due to an abnormality in its stimulus or use.
    • Visual acuity loss is recoverable with treatment.

    Types of Functional Amblyopia

    • Form Vision Deprivation Amblyopia (Amblyopia Ex-Anopsia)
      • Caused by physical obstruction along the line of sight, preventing the formation of a well-focused, high-contrast image on the retina.
      • Prevalence: 0.1% in general population, 5-10% of all amblyopia.
      • Clinical characteristics:
        • Often severe acuity loss (>20/200)
        • Unilateral or bilateral
        • History may include: congenital cataract, traumatic cataract, corneal opacities, severe ptosis, hyphema, vitreous clouding, prolonged uncontrolled patching, and shaken baby syndrome.
    • Refractive Amblyopia
      • Caused by high but equal (isoametropic) or clinically significant unequal (anisometropic) uncorrected refractive errors.
    • Isoametropic Amblyopia
      • Caused by high but equal uncorrected bilateral refractive error.
      • Prevalence: 1-2% of refractive amblyopes.
      • Clinical characteristics:
        • Bilateral reduced visual acuity
        • Associated with high refractive error (astigmatism >2.50 D, hyperopia >5.00 D, myopia >8.00 D)
        • Corrected VA of 20/30 to 20/60
        • Often associated with strabismus and other developmental anomalies
    • Anisometropic Amblyopia
      • Caused by uncorrected refractive error in which the difference between the corresponding major meridians of the two eyes is at least 1 D.
      • Prevalence: 1/3 of all amblyopes, 1/3 combined with strab as the etiology
      • Clinical characteristics:
        • All anisometropes: ~20% amblyopic
        • Form Deprivation: lack of clear image affects neurodevelopment of cortical mechanisms involved in form and shape perception
        • Suppression (Competitive, binocular inhibitory effect): occurs cortically where binocular interaction takes place

    Amblyogenic Mechanisms

    • Two major mechanisms involved in functional amblyopia:
      • Form Deprivation
      • Suppression (Competitive, binocular inhibitory effect)

    Organic Vision Loss

    • Definition: Occurs when the components of the visual pathway fail to develop or become impaired due to structural defects or metabolic/toxic disturbances.
    • Can be either bilateral or unilateral, irreversibly reduced vision attributed to congenital or hereditary anomalies in the visual receptors or visual pathways.

    Psychogenic Vision Loss

    • Definition: Vision loss that occurs from emotional or psychological rather than physiological origin.
    • Symptoms are not under voluntary control.
    • Clinical features:
      • Bilateral reduced VA (20/70 – 20/200)
      • Normal ocular health
      • Minor symmetric refractive error (usually emmetropia or hyperopia)
      • Normal binocular vision (no strabismus, but may report diplopia)
      • Orthophoria or small heterophoria
      • Abnormal visual fields
    • Treatment: Reassurance, referral to psychologist or psychiatrist, low plus lenses often help.

    Relative Amblyopia

    • Strabismic Amblyopia
      • Caused by early onset (< 6 or 8 years of age) constant unilateral strabismus.
      • Prevalence: 1/3 of amblyopes, another 1/3 combined with anisometropia etiology.
      • Clinical characteristics:
        • No relationship between depth of amblyopia and size of strabismus
        • Mean VA of strabismic amblyopes: ~20/70
    • Amblyogenic Mechanisms
      • Minor: accommodation controlled by fixating eye, so foveal image of deviating eye may be out of focus some of the time
      • Major: corresponding points in the two retinas receive different stimuli, creating confusion and diplopia.

    Diagnostic Tests

    • Normal in functional amblyopia:
      • Ophthalmoscopy
      • Pupils
      • Amsler grid
      • Visual field
      • Photostress Test
    • Neutral Density Filter:
      • Take VA, use 3.0 Neutral Density filter, dark adapt patient (5min), recheck VA
      • Normal eyes drop between 20-50% Snell-Sterling
      • Functional amblyopia: VA will stay about the same
      • If pathology or organic etiology: see drastic decrease in VA

    Eccentric Fixation (EF)

    • EF is the use of an off-foveal site during monocular viewing
    • There is a relationship between the amount of EF and the reduced VA in amblyopia
    • EF may mask or fool us when evaluating for strabismus
    • EF contaminates our evaluation of:
      • Magnitude of deviation (underestimation or overestimation)
      • Angle of anomaly

    Incidence of EF

    • High for Strab/Amb (~60-80%)
    • Low for Aniso/Amb (~10-20%)

    Classification of EF

    • Localization
    • Location (part of the retina used for fixation, e.g. temporal, nasal, superior, inferior)
    • Magnitude (measured in prism diopters, e.g. parafoveolar, paramacular, peripheral)
    • Stability (steady vs. unsteady)

    Diagnostic Methods

    • Visuoscopy
      • Objective evaluation
      • Projection of calibrated target on the retina
      • Instructions: demo first with good eye, project into amblyopic eye, assess location of retina used to fixate target
    • Haidinger's Brushes Test
      • Subjective evaluation
      • Entopically perceived pattern of closely packed radiating lines
      • Instructions: patient wears blue gelatin filter, locates brush in relationship to fixation target
      • EF = Brush and Fixation mark not coincident
    • Brock-Givner After Image Transfer Test
      • Based on assumption that patient has normal correspondence
      • Instructions: flash vertical AI on fovea of normal eye, occlude normal eye, direct patient to fixation mark with amblyopic eye, determine direction and magnitude of EF

    Key Concepts

    • Eccentric Fixation is NOT the same as eccentric viewing
    • Eccentric Fixation (Monocular) is NOT the same as Fixation Disparity (Binocular)
    • Only 10% of time is EF opposite in direction to the strabismus (post-surgical)
    • Can use low light level or green filter to reduce glare for patient during visuoscopy testing

    Anomalies of Binocular Vision - Strabismus/Amblyopia Diagnosis

    Diagnostic Characteristics of Ocular Motor Deviation

    • Direction: esotropia, exotropia, vertical, cyclo
    • Frequency: intermittent, constant
    • Magnitude: measured in prism diopters at distance and near
    • Laterality: unilateral, alternating with preferred eye
    • AC/A Ratio: low, normal, high
    • Cosmesis: poor, fair, good
    • Concomitancy: magnitude in all fields of gaze with either eye fixating
      • Concomitant Esotropia: CE, BE, DI
      • Concomitant Exotropia: CI, BX, DE

    Diagnostic Methods

    • Direct Observation
      • Cosmesis of eye turn: grade as Good, Fair, Poor
      • Lid fissure: ptosis vs. non-ptosis

    UCT Testing

    • 20D esophoria: ?
    • 20D exotropia: ?
    • 10D right hyperphoria: ?
    • 10D left hypotropia: ?

    Primary and Secondary Vertical

    • Difference between primary and secondary vertical

    4DBO Test

    • Results on a patient with normal Binocular Vision (BV)
    • Results on a patient with 8D constant Left Eye Trope (LET)

    Double Maddox Rod Method

    • Patient with right ex-cyclodeviation of 10°: reports ?

    Strabismus

    • Concomitant deviation: angle of deviation remains the same throughout all positions of gaze and with either eye fixating
    • Nonconcomitant deviation: angle of deviation changes in different fields of gaze or with either eye fixating

    Causes of Strabismus

    • Anatomical: effects of tendons, abnormalities of EOM’s, check ligaments, orbital contents (low prevalence)
    • Optical: refractive anisometropia, high refractive error, media opacities (high prevalence)
    • Innervational: muscle tonus or innervational changes from intoxication, medications, trauma or disease, innervational anomalies, congenital, high or low AC/A ratios (high prevalence)

    Characteristics of Deviations

    • If the magnitude of the deviation cannot be overcome by fusional vergence, the deviation may manifest
    • Any disruption of the sensory fusion system may result in the deviation being manifest
    • Most concomitant deviations are supranuclear in origin, where most nonconcomitant deviations are nuclear or infranuclear

    Etiologies of Acquired 3,4,6 Nerve Paresis

    • 26.2% cause undetermined
    • 19.7% head trauma
    • 17.2% vascular
    • 14.3% neoplasm
    • 7.1% aneurysm
    • 15.4% other

    Most Common Causes of Strabismus

    • Adults: trauma, vascular, neoplasm
    • Children: acute viral illness, trauma, congenital nerve paresis

    Physiological Principles

    • Hering’s Law of Equal Innervation: contralateral synergists are equally innervated
    • Sherrington’s Law: contraction of a muscle is accompanied by a simultaneous and proportional relaxation of its antagonist
    • Innervation of EOM’s:
      • CN3 (Oculomotor) innervates MR, SR, IR, IO
      • CN4 (Trochlear) innervates SO
      • CN6 (Abducens) innervates LR

    Diagnostic Testing Methods

    • Direct observation to identify an obvious abnormal head position
    • Patch Test: to differentiate between ocular and congenital torticollis
    • Version Testing: to detect any change in eye position (underacting-UA, overacting-OA)
    • Hirschberg testing: to assess the integrity of oculomotor innervation balance between the two eyes

    Muscle Actions

    • 3 main reasons for muscle underactions:
      • Muscles themselves may be paretic as in cases of direct traumatic injury
      • Mechanical reasons such as faulty muscle insertions and ligament or tendon abnormalities
      • Innervational deficiencies due to impairment of the cranial nerves (3, 4, 6)
    • Possible reasons for muscle overactions:
      • Mechanical reasons, faulty muscle insertion giving mechanical advantage to particular muscle
      • MORE OFTEN - overaction can be explained by Hering’s law of equal innervation

    Isolating Muscle Actions

    • Rectus Muscles: 23° angle between the lines of insertion and the visual axis, inserted forward of the equator of the eye
    • Oblique Muscles: 51° angle between the lines of insertion and the visual axis, inserted behind the equator of the eye
    • How to isolate the action of single muscles or yoked muscle pairs: position eyes so the visual axis and the lines of insertion are coincident

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    Description

    Learn about the basics of strabismus and amblyopia diagnosis, including their definitions, prevalence, and leading causes. This introductory lecture covers key concepts in binocular vision anomalies.

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