Spectacle Magnification and Unequal Refractive Errors

Question 1

What does the prefix “a” or “an” indicate?

Answer 1

Not, or without

Question 2

What does the prefix “iso” indicate?

Answer 2

equal

Question 3

A wildly fluctuating refraction is frequently caused by what?

Answer 3

Diabetes

Question 4

Vertical imbalances are caused by anisometropia in which meridian?

Answer 4

90th

Question 5

The problem of unequal retinal image sizes is called what?

Answer 5

aniseikonia

Question 6

If the optical center of a minus lens is moved nasally, it creates prism whose base is in which direction?

Answer 6

Out

Question 7

If the rx is OU +3.00 sphere, and both eyes deviate 10mm upward, what is the prismatic effect at that point?

Answer 7

Zero - there is no prismatic effect

Question 8

In the rx pl +2.00 x180, what is the total power in the 30th meridian? Remember the Percentage Cylinder Power chart!

Answer 8

+0.50

Question 9

In the rx -3.00 -3.00 x090, what is the total power in the 30th meridian? Remember the Percentage Cylinder Power chart!

Answer 9

-4.50

Question 10

One of the common problems experienced by anisometropic spectacle wearers is what?

Answer 10

motility/diplopia

Question 11

Anisometropia is almost always a problem with which type of patient?

Answer 11

Presbyope

Question 12

Bicentric grinding (slab-off) in bifocals result in prism. Which direction does this prism go?

Answer 12

Base up

Question 13

Slab-off should not be ordered for imbalance under what dioptric power?

Answer 13

1.5

Question 14

Slab-off can be measured by using what device?

Answer 14

Lens clock

Question 15

Slab-off is placed in which lens?

Answer 15

Most minus, least plus

Question 16

In selecting frames for anisometropic presbyopic patients, what parameter should be followed? Symmetrical lens, small eye size, proper centration

Answer 16

All of these shapes

Question 17

For large increments of rx change, increasing the power in gradual, temporary steps may be more economically feasible by using what?

Answer 17

Fresnel lenses

Question 18

Anisometropic symptoms may include all of the following except for what? Headaches, pulling and drawing sensations, increased intraocular pressure, burning and itching

Answer 18

Increased intraocular pressure

Question 19

The preferred method of prismatic compensation for patients who cannot tolerate looking below the optical centers is what?

Answer 19

Slab-off

Question 20

The uncorrected anisometrope will generally learn to adjust by doing what?

Answer 20

Dropping the head to read

Question 21

The following rx is an indication of what type of disorder?
OD: -5.00 -1.00 x180
OS: +2.00 -1.00 x180

Answer 21

Antimetropia

Question 22

The following rx is an indication of what type of disorder?
OD: +5.00 -1.00 x180
OS: +2.00 -1.00 x180

Answer 22

Anisometropia

Question 23

What is the name of the condition whereby two unequal images are sent by the eyes to the brain?

Answer 23

Aniseikonia. It can be sub-divided into two different conditions: Antimetropia, where one eye is myopic and the other eye is hyperopic; and Anisometropia, where both eyes are either myopic or hyperopic but there is a sizable difference in prescription.

Question 24

What variables are used to produce iseikonic lenses?

Answer 24

base curve, center thickness, index of refraction, vertex distance

Question 25

Left uncorrected, aniseikonia may result in what condition?

Answer 25

Amblyopia, or lazy eye

Question 26

As a plus lens is moved further away from the eye, the effect on magnification is what?

Answer 26

Magnification increases

Question 27

As a minus lens is moved further away from the eye, the effect on magnification is what?

Answer 27

Magnification increases

Question 28

As a rule of thumb, differences in magnification over ___ from eye to eye are usually problematic to the wearer.

Answer 28

5%

Question 29

In addition to magnification/minification problems, a wearer with unequal refractive errors may experience what visual disturbance?

Answer 29

Vertical imbalance

Question 30

Correction for visual imbalance could include all of the following except: Slab-off, two pairs of eyewear, aniseikonic lenses, or dissimilar segments

Answer 30

Aniseikonic lenses