Amblyopia (M2) Flashcards
(41 cards)
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