Podcast
Questions and Answers
What happens to astigmatism when scoping off-axis?
What happens to astigmatism when scoping off-axis?
How do you scope a constant ET on axis?
How do you scope a constant ET on axis?
What is the recommended working distance for the Near Retinoscopy Method (Mohindra)?
What is the recommended working distance for the Near Retinoscopy Method (Mohindra)?
What is the dosage of Cyclopentolate for a 3-year-old?
What is the dosage of Cyclopentolate for a 3-year-old?
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What is one way to determine if you have adequate cycloplegia?
What is one way to determine if you have adequate cycloplegia?
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What happens to the spherical component when scoping off-axis?
What happens to the spherical component when scoping off-axis?
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What is the purpose of subtracting 1.25 D from the sphere value in the Near Retinoscopy Method (Mohindra)?
What is the purpose of subtracting 1.25 D from the sphere value in the Near Retinoscopy Method (Mohindra)?
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What is the recommended dosage of Cyclopentolate for an 8-month-old?
What is the recommended dosage of Cyclopentolate for an 8-month-old?
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What is the primary purpose of keratometry?
What is the primary purpose of keratometry?
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In non-cycloplegic static retinoscopy, what is done for out-of-phoropter refraction for children and deviations > 15∆?
In non-cycloplegic static retinoscopy, what is done for out-of-phoropter refraction for children and deviations > 15∆?
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What is the working distance in the Near Retinoscopy Method (Mohindra)?
What is the working distance in the Near Retinoscopy Method (Mohindra)?
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What is the duration of action of Tropicamide?
What is the duration of action of Tropicamide?
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What is the dosage of Cyclopentolate for children under 1 year?
What is the dosage of Cyclopentolate for children under 1 year?
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What is the toxicity symptom of Atropine?
What is the toxicity symptom of Atropine?
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How is the adequacy of Cycloplegia determined?
How is the adequacy of Cycloplegia determined?
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What amount of hyperopia is associated with the future development of esotropia (ET) and amblyopia?
What amount of hyperopia is associated with the future development of esotropia (ET) and amblyopia?
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What factor needs to be controlled when performing retinoscopy on a patient with strabismus?
What factor needs to be controlled when performing retinoscopy on a patient with strabismus?
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What is the characteristic of Tropicamide?
What is the characteristic of Tropicamide?
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What percentage of children with strabismus have abnormal refractions?
What percentage of children with strabismus have abnormal refractions?
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What is the refractive power difference between the two eyes that commonly causes amblyopia?
What is the refractive power difference between the two eyes that commonly causes amblyopia?
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What is the effect of increased accommodation on refractive error?
What is the effect of increased accommodation on refractive error?
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What is the percentage of amblyopia cases caused by anisometropia?
What is the percentage of amblyopia cases caused by anisometropia?
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What is the refractive error that increases the risk of strabismus by 20 times in children at 1 year?
What is the refractive error that increases the risk of strabismus by 20 times in children at 1 year?
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What is the effect of retinal eccentricity on astigmatism?
What is the effect of retinal eccentricity on astigmatism?
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What is the degree of visual axis deviation to avoid significant errors in astigmatic and spherical components?
What is the degree of visual axis deviation to avoid significant errors in astigmatic and spherical components?
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What percentage of comitant esotropias resolve with corrective lenses?
What percentage of comitant esotropias resolve with corrective lenses?
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Study Notes
Refractive Status in Strabismus and Amblyopia
Importance of Refractive Status
- Refractive status is a crucial factor in the etiology of strabismus and amblyopia
- Strabismus is often caused by refractive issues
- Amblyopia is commonly caused by anisometropia (unequal refractive power between the two eyes)
Key Findings
- One-third of comitant esotropias (ETs) resolve with corrective lenses
- Approximately 50% of amblyopia cases are caused by anisometropia
- 72% of children with strabismus have abnormal refractions
- Refractive errors leading to strabismus and amblyopia:
- Hyperopia > +2.00 D
- Anisometropia > +1.00 D in any meridian
- Children with hyperopia > +2.50 D at 1 year are 20 times more likely to develop strabismus
- Hyperopia > +3.50 D at 6-8 months increases the risk of strabismus by 13 times and amblyopia by 6 times 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 degrees (~17∆) of the visual axis to avoid significant errors in astigmatic and spherical components
Controlling Accommodation
- Increased accommodation results in an artificial increase in negative or decrease in positive refractive error
- Indicators of accommodation:
- Abnormally small pupils or decreasing pupil size beyond normal miosis during retinoscopy
- Use projected targets or cartoons to control accommodation effectively
Keratometry
- Purpose: Confirm astigmatic power and axis found by retinoscopy
Noncycloplegic Static Retinoscopy
- Procedure:
- Initial screening
- Scoping strabismic patients:
- For ETs and vertical deviations: Hold correcting prism in front of the fixating eye
- For XTs: Align Purkinje's images or use a corrective prism base in (BI)
- Considerations:
- Out-of-phoropter refraction for children and deviations > 15∆
- Astigmatism increases and spherical power decreases as you go off-axis
Near Retinoscopy Method (Mohindra)
- Procedure:
- Patient sits in a chair or on a parent's lap
- 50 cm working distance with room lights out
- Patient fixates on the retinoscope; monitor corneal reflex to ensure scoping on axis
- One eye occluded
- Neutralize primary meridians and subtract 1.25 D from the sphere value (for children > 2 years, subtract 1.00 D)
- Comparison: Correlates with cycloplegic methods about 35% of the time
- Improvements: Use 1.00 D for children and 0.75 D for infants instead of 1.25 D; NRM may slightly underestimate hyperopia
Cycloplegic Retinoscopy
- Tropicamide:
- Characteristics: Short duration of action, brief peak time, poor at eliminating high accommodative tonus of childhood
- Not recommended for cycloplegia
- Response: Mydriasis in 20-40 min, Cycloplegia in 60-180 min
- Cyclopentolate (Cyclogyl):
- Dosage:
- < 1 year: 0.5% solution, 2 drops (1 drop, wait 5 min, add 1 drop)
- 1 year: 1.0% solution, 2 drops (1 drop, wait 5 min, add 1 drop)
- Response: Mydriasis within 30-60 min, Cycloplegia max in 30-45 min
- Duration: Mydriasis for ~24 hours, Cycloplegia for 8-24 hours
- Toxicity symptoms: Restlessness, hallucinations, memory loss, etc
- Dosage:
- Atropine:
- Dosage:
- < 1 year: 0.5% ointment/solution BID x 3 days before exam
- 1 year: 1.0% ointment/solution BID x 3 days before exam
- Response: Mydriasis in 30-45 min, Cycloplegia max in 3-6 hours
- Duration: Mydriasis for up to 12 days, Cycloplegia for 10-18 days
- Toxicity symptoms: Dry skin, fever, tachycardia, delirium
- Dosage:
Determining Adequacy of Cycloplegia
- Pupil size is not an indicator
- Look for < 2D accommodative amplitude or a +2.00D lag in dynamic retinoscopy
- Use a single line of threshold Snellen at distance; if adding -0.75 D reduces visual acuity (VA), adequate cycloplegia is achieved
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Description
Learn about the importance of refractive status in strabismus and amblyopia, including their causes and effects. Discover how corrective lenses can resolve comitant esotropias and more.
