Unit 2

Question 1

What is the standard prism tolerance in eyeglasses?

Answer 1

1/2 prism

Question 2

If two images of an object fall on identical points on the retina, the object is seen as ______.

Answer 2

One

Question 3

If 2 vertical prisms are in the same direction, do we add them or do they cancel each other out?

Answer 3

Cancel

Question 4

We split a prism between the eyes when it is ___ or more diopters.

Answer 4

2

Question 5

Two horizontal prisms going in the same direction - do we add them together or do they cancel each other out?

Answer 5

add

Question 6

Two horizontal prisms going in opposite directions - do we add them together or do they cancel each other out?

Answer 6

cancel

Question 7

Comparing the eye to a camera, the retina would be the _____.

Answer 7

film

Question 8

Comparing the eye to a camera, the cornea is the ____ of the eye.

Answer 8

lens

Question 9

How tall are the Snellen letters at the 20/20 line?

Answer 9

8.87 mm

Question 10

Glasses are prescribed for which 3 reasons?

Answer 10

1. refractive errors
2. comfort
3. safety

Question 11

Define asthenopia.

Answer 11

uncomfortable vision

Question 12

Define orthophoria.

Answer 12

the eyes are aligned straight

Question 13

At age 10, our eyes can accommodate ____ diopters.

Answer 13

14

Question 14

A plus lens decentered down produces prism base ____.

Answer 14

down

Question 15

What is the Prentice’s Rule for calculating prism?

Answer 15

prism = Dd/10

Question 16

How do we calculate decentration?

Answer 16

decentration = 1/2( frame PD - patient’s PD)

Question 17

How do we calculate monocular decentration?

Answer 17

mono. dec. = 1/2(frame PD) - patient’s mono PD

Question 18

Prisms deviate light towards the _____.

Answer 18

base

Question 19

Prisms displace images toward the _____.

Answer 19

apex

Question 20

Prisms are prescribed for phorias and _____.

Answer 20

tropias

Question 21

A tendency of the eye to turn in or out.

Answer 21

phoria

Question 22

The eye is permanently turned in or out.

Answer 22

tropia

Question 23

How do we calculate the amount of decentration needed to produce a prescribed prism?

Answer 23

decentration = A10/D

A=prism

Question 24

For plus lenses, the direction of decentration is in the _______ direction.

Answer 24

same

Question 25

For minus lenses, the direction of decentration is in the _______ direction.

Answer 25

opposite

Question 26

A minus lens decentered down produces prism base _____.

Answer 26

up

Question 27

How tall are the Snellen letters at 20/40?

Answer 27

17.74 mm

Question 28

Presbyopia is a refractive error.

Answer 28

False - it is a condition, not an error.

Question 29

A hyperopic child tends to ____ - converge and ____ accommodate.

Answer 29

over, over

Question 30

A hyperopic child's eyes may lead to _______ if not corrected.

Answer 30

esophoria (tendency to turn in)

Question 31

A myope tends to ______ converge and ____ accommodate.

Answer 31

under, under

Question 32

An uncorrected myopic child's eyes may have the tendency to turn ______.

Answer 32

out (exophoria)

Question 33

At age 40, we have the ability, on average, to accommodate ____ diopters.

Answer 33

4.5