Lecture 16 - Anisometropia & Anisikonia

Question 1

define anisometropia

Answer 1

a condition of unequal refractive state for the two eyes, one eye requiring a diff lens correction from the other

Question 2

when is anisometropia clinically significant

Answer 2

when the spherical equivalent of the two eyes differ by a 1 D or more

Question 3

Two types of ametropia are ____ametropia which includes hyperopia (eye is too short) and myopia (eye is too long), also _____ ametropia which includes hyperopia (the refractive power is too low) and myopia (the refractive power is too high)

Answer 3

axial; refractive

Question 4

In axial ametropia, the image size is almost without magnification with _____. Image size with ____ is greater for myopes and less for hyperopes

Answer 4

spectacles; contacts

Question 5

In refractive ametropia, image size is almost without magnification with _____. Image size is greater with _____ for hype ropes and less for myopes.

Answer 5

contacts; spectacles

Question 6

The ____ eye will have a larger retinal image with contact lenses if its _____ ametropia

Answer 6

myopic; axial

Question 7

The ____ eye will have a smaller retinal image with contact lenses.

Answer 7

hyperopic

Question 8

what is the major contributing factor in regards to high anisometropia?

Answer 8

axial length

Question 9

If the corneal power is the same or very similar between the two eyes what type of anisometropia is it?

Answer 9

axial

Question 10

If the corneal power is greater in one eye what type of anisometropia is it?

Answer 10

refractive

Question 11

What are the two main reasons for amblyopia?

Answer 11

1. anisometropia

2. strabismus

Question 12

What are signs of uncorrected anisometropia

Answer 12

1. Reduced depth perception
2. Unequal accommodation
3. Images between the eyes differ in clarity, contrast and size
4. Amblyopia

Question 13

Refractive amblyopia occurs in myopic patients who have an anisometropia of greater than _____ D

Answer 13

3.00

Question 14

Refractive amblyopia occurs in hyperopic patients who have an anisometropia of greater than ____D

Answer 14

1.00

Question 15

Refractive amblyopia occurs in astigmatic puts who have an anisometropia of greater than ____D

Answer 15

1.50

Question 16

Why is hyperopic anisometropia more problematic and more amblyogenic than myopic anisometropia?

Answer 16

Myopic puts can use mono vision and still see clearly at least at near. Hyperopic patients may not have enough accommodation to see clearly at any distance

Question 17

What are some downsides to correcting anisometropia?

Answer 17

1. vergence problems

2. anisikonia

Question 18

What is the equation for determining prismatic effect?

Answer 18

power x decantation in cm

*10 mm = 1 cm

Question 19

What plays a role in vertical imbalance?

Answer 19

distance assymmetry, NOT the seg

Question 20

what is the definition of aniseikonia

Answer 20

a relative difference in size/shape of the ocular images.

Question 21

What are signs of aniseikonia?

Answer 21

1. anisometropia
2. aphakia in one eye
3. large amounts of astigmatism
4. reduced stereo acuity
5. strabismus
6. amblyopia

Question 22

what are types of aniseikonia

Answer 22

1. refractive
2. axial
3. meridional

Question 23

With spectacle magnification, the retinal image will be larger in the direction of the ___ of the minus cylinder

Answer 23

axis

Question 24

For spectacle lenses, for each 1.0 D of cylinder difference between the two principal meridians, there is about _____ % difference in SM

Answer 24

1.5%

Question 25

For contact lenses, for each 1.0D of cylinder difference between the two principal meridians, there is about ____% difference in SM

Answer 25

0.3

Question 26

Minimal change in the image size will occur in ____ ametropia with spectacle correction

Answer 26

axial

Question 27

Minimal change in the image size will occur in ___ ametropia with contact lenses

Answer 27

refractive

Question 28

For a patient with normal binocular vision, an image sizes difference between the two eyes of greater than ____% is rarely found

Answer 28

5