Amblyopia (M2) Flashcards
What is the idea that resolution ability is related to the proximity of the acuity targets? 1. What can this cause an abnormality in? 2
- crowding phenomenon
2. contour interaction
What is the ATS Visual acuity protocol?
- screening until one missed
- phase I: start 2 LogMAR levels above missed in screening and determine lowest level with 3 of 4 or better
- reinforcement: 3 larger letters shown
- phase II: repeat last level missed in phase I and continue until fail
- VA: lowest level passed in phase I or II
What population is ETDRS VA used for? 1. HOTV? 2
- 7yo and older
2. younger kids
Do HOTV VA’s over or underestimate VA (and by how much)?
- overestimates by 0.68 lines in amblyopic eye
2. over by 0.25 in good eye
What is the S chart procedure measuring? 1. How is the measurement found? 2
- psychometric VA
2. VA is where line intersects 5 correct in the S
What is used for amblyopia assessment in infants (how do the tests compare)?
- Teller acuity cards
2. Vernier acuity cards (higher sensitivity)
Is the optotype VA or the grating VA better in amblyopic eyes?
grating acuity
What are the ways to assess fixation preference in an amblyopic patient?
- binocular fixation pattern in strabismus
- induced tropia test in children with small angle or no strab
- assess monocular fixation under binocular conditions
4.
Describe the grade 0 fixation preference? 1. Grade 1? 2. Grade 2? 3. Grade 4? 5
- fixating eye immediately resumes fixation after removal of the occluder (absolute)
- deviating eye can hold fixation momentarily (strong)
- deviating eye can hold fixation until the next blink (moderate)
- deviating eye can hold fixation through the next blink (slight)
- equal alternation between two eyes (none)
What is the contrast sensitivity like for an aniso amblyope? 1. Strabismic amblyope? 2
- loss over entire spatial frequency range (more uniform and extensive)
- loss of primarily high frequencies (more asymmetric and less severe)
What kind of refraction should be done on an amblyope?
binocular
What are the effects of amblyopia on the pupils?
some patients have mild APD with a longer latency of contraction
What should be used to determine if the fixation is central or eccentric?
- visuoscopy
2. MITT box or Maxwell’s spot
What is used to determine suppression in amblyopic patient?
- orthoscope
2. Worth dot
What is the suppression like in anisometropic amblyopia? 1. Isoametropic amblyopia? 2
- small relative (not absolute) foveal suppression area
2. can have no suppression, suppression in either eye or suppression in amblyopic eye
What patients are at an increased risk of amblyopia?
- prematurity
- low birth weight
- retinopathy of prematurity
- mental retardation
- cerebral palsy
- maternal smoking or drug use during pregnancy
How is amblyopia clinically defined with base don findings?
- VA 20/40 or less in one eye
2. two line difference between the two eyes
What are the retinal characteristics of an amblyope?
- abnormal ERG findings
- no NFL difference
- normal retinal function
- subfoveal choroid of eyes with hyper aniso is thicker
What are the characteristics of the structures post retina (brain, etc)?
- delayed neural conduction in postretinal visual pathways
- shrinkage of cells in LGN
- visual cortex has shift of dominance to nondeviating eye and inc in cortical response to amblyopic eye for a unilateral strab
What is the susceptibility period from 0 to 3yo for amblyopia development called? 1. 3 to 10yo? 2. After 10yo? 3
- critical period
- sensitive period
- plastic period
What was found to be the age when you would stop treating aniso amblyopia?
none. treat all ages
What percentage of amblyopes improve with optical correction alone for ages 7 to 18?
25%
What was found to be the results of additional amblyopia treatment beyond just optical correction for ages 7 to less than 13? 1. Ages 13 to 18? 2
- additional improvement seen with patching and atropine
2. additional improvement only seen if patient had never been treated for amblyopia before
What is the minimum hyperopic refractive error that can lead to anisometropic amblyopia? 1. Myopic RE? 2. Astigmatic RE? 3
- over 1D
- over 2D
- over 1.5D
What is the minimum hyperopic refractive error that can lead to isoametropic amblyopia? 1. Myopic RE? 2. Astigmatic RE? 3
- over 5D
- over 8D
- over 2D
How is the telescopic visual acuity used to predict improvement of amblyopia with treatment?
2X telescope should improve VA by a factor of two or more (if does means favorable prognosis)
How is the visual evoked potential (VEP) used to predict improvement of amblyopia with treatment?
waveform of amblyopic eye has dec amplitude and inc latency. When compare monocular and binocular, if have binocular summation and binocular response similar to good eye then good prognosis
What type of lens material should always be prescribed to amblyopes and why?
polycarb or trivex because greater risk of blindng injury to good eye
What are the important aspects of a patients glasses that need to be measured in the correction of RE for an amblyope?
- measure pd
- meausre vert pupil height
- check frame fit, temple length
- B size
What percentage of aniso, strabismic and combined ambyopes will not need further treatment beyond correcting refractive error? 1. How long do you follow this? 2
- 25 to 33%
2. follow with glasses only until 2 stable acuities 4 weeks apart or 16 weeks
What are the important aspects that the parent must understand about their child’s amblyopia?
- Diagnosis - Use Demo’s
- Each plan and rationale
- Need to adapt to Rx
- Further treatment may be needed
- Refinements in Rx
- Advise parent if risk of consecutive exotropia
What is the follow up schedule for a patient being treated for amblyopia?
every 4 to 6 wks until 2 visits with stable VAs or about 4 months
What a common the potential side effect of patching?
skin irritation
What must you do before prescribing atropine as a treatment for amblyopia?
- measure VA of each eye with full cycloplegic correction
2. educate parent on dilated pupil and 1gtt only
What is the effect of amblyopia therapy on ocular alignment?
similar for atropine and patching. May deteriorate alignment or improve to ortho
What are the considerations for choosing atropine or patching?
- preference of family (tend to like atropine)
- refractive correction of good eye (if myopic)
- latent nystagmus (atropine better for these people)
What are the thoughts on the use of Bangerter’s foil as therapy for amblyopia?
- Not as good as patching or atropine
2. reasonable option though for moderate amblyopia
What are good ways to prevent regression in children under 8yo?
- Rx wear
- orthoptic therapy
- tapering occlusion
- maintenance therapy
Should patients be weaned off patching?
yes if 6 or more hours of daily patching was Tx
What is the percentage of recurrence over 1 year after treatment of amblyopia? 1. When do most recurrences occur? 2. What children are at higher risk of this? 3
- 25%
- 3 months
- combined amblyopia
What are the residual deficits of treated amblyopes?
- residual amblyopia
- stereoacuity often below normal
- reading rate, accuracy and fluency worse in treated amblyopic eye compared to good eye
