Anisometropia- Dr. Farra Flashcards Preview

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what is anisoametropia

condition in which the refractive status of one eye differs from that of another (>1D)


what is low difference and high diff classified as

at what D will the pt suppress 1 eye

low: < 2.00D
high: > 2.00D

>5D not usually a problem bc pt will most likely suppress 1 eye


what is antimetropia

different types of refractive errors in the 2 eyes
ex. one myopic one hyper


what are the signs and symptoms of anisoametropia

-reduced steropsis
-abnormal binocularity


why is anisometrpia a problem

if not fully corrected, may lead to amblyopia or poor binocularity


what is hering's law

the 2 eyes accommodate equally, therefore, an uncorrected anisometrope can nver have clear retinal images in both eyes simultaneously


what is the lag of accomadation at near

+0.50D lag of acc at near


what are the amblyogenic refractive errors?

amblyo only if present in children

-astig > 1.5D
-hyperopia > 1.00D
-myopia > 3.00D

-asig >2.5D
-hyper > 5.00D
-myopia > 8.00D


if aniso is fully corrected, it still may lead to...

anisophoria: unequal prismatic effects

aniseikonia: unequal image sizes


for horizontal effects, what are some solutions
what about for vertical effects

horiz: go with a small lens
-pt ed to move head instead of eyes

vert: NVO for reading, w/ ocs lowered 5-10mm from distance position
-prescribe "slab off" if pt needs a bifocal


where should the location of the slab off coincide w/

the locatino of the slab off should coincide w/ the location of the bifocal line height


what is the power range of slab-off

prism power range you could get with slabbing is about 1-6 diopter range


what are the symptoms of aniseikonia

-asthenopia (HA) -67%
-perceptual distortions of space: vertigo/dizziness (a less common incidence, but is most diagnostic) -6%


there are 2 types of anisometropia. what are they and what do you measure to tell the difference?

axial and refractive
-measure corneal curvature to tell the difference


according to knapp's law what do you correct an axial aniso w/? what about refractive?
in reality what do you correc t/

axial: theory is correct w/ specs
realiality is correct w/ cl

refractive: theory is correct w/ cl, reality correct w/ fl


if you need compensate for anisekonia...
-_____ the base curve to magnify the img
-______ the center thickness to magnify the image
-always ______ the vertex distance to equalize the imgs better (contact lens theory)

-steepen/increase the bc to magnify the img
-increase the center thickness to magnify the img
-always minimize the vertex distance to equalize the imgs better (cl theory)


when should you be worried about aniseikonia???!?!?
consider a ____% img size difference for every diopter of aniso
-generally, a _____% img size difference (ISD) can be fused but it is not happy fusion
- >__% ISD is poor fusion w/ symptoms
- > ___% ISD is no fusion-a set up for diplopia, suppresion, and optical confusion

-1% img size diff every every D of anisometropia
-1-2.5% img size diff can be fused but it is not happy fusion
- >3% ISD is poor fusion w/ symptoms
- >5% is no fusion-a set up for diplopia, suppression, and optical confusion


what does the tolerance for aniso Rx depend on (4)

1. pt age
2. amt of aniso
3. prior spec history
4. fusion capability


if amblyopia is present, do you perform binocular balance?

fk no