Anisometropia- Dr. Farra

Question 1

what is anisoametropia

Answer 1

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

Question 2

what is low difference and high diff classified as

at what D will the pt suppress 1 eye

Answer 2

low: < 2.00D
high: > 2.00D

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

Question 3

what is antimetropia

Answer 3

different types of refractive errors in the 2 eyes

ex. one myopic one hyper

Question 4

what are the signs and symptoms of anisoametropia

Answer 4

SYMP
-asthenopia 
-headache
-none 
SIGNS
-reduced steropsis
-abnormal binocularity
-suppression
-amblyopia

Question 5

why is anisometrpia a problem

Answer 5

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

Question 6

what is hering’s law

Answer 6

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

Question 7

what is the lag of accomadation at near

Answer 7

+0.50D lag of acc at near

Question 8

what are the amblyogenic refractive errors?

amblyo only if present in children

Answer 8

aniso

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

isoametropia

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

Question 9

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

Answer 9

anisophoria: unequal prismatic effects
aniseikonia: unequal image sizes

Question 10

for horizontal effects, what are some solutions

what about for vertical effects

Answer 10

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

Question 11

where should the location of the slab off coincide w/

Answer 11

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

Question 12

what is the power range of slab-off

Answer 12

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

Question 13

what are the symptoms of aniseikonia

Answer 13

• asthenopia (HA) -67%

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

Question 14

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

Answer 14

axial and refractive

-measure corneal curvature to tell the difference

Question 15

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

Answer 15

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

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

Question 16

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)

Answer 16

• 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)

Question 17

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

Answer 17

• 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

Question 18

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

Answer 18

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

Question 19

if amblyopia is present, do you perform binocular balance?

Answer 19

fk no