Refractive Errors

Question 1

To do a spherical equivalent ___.

Answer 1

Take half of the cylinder and algebraically add it to the sphere power, vertex as necessary and that is your beginning power.

Question 2

Spherical (sphere) lenses are lenses with a single dioptric value and have what in all meridians?

Answer 2

The same curvature

Question 3

The orientation of powers (curves) on the surface of lenses are what?

Answer 3

Meridians

Question 4

This prescription exhibits what type of astigmatism? -2.50 +1.50 X 180

Answer 4

Compound myopic astigmatism

Question 5

This prescription exhibits what type of astigmatism? -2.50 +2.50 X 180

Answer 5

Simple hyperopic astigmatism

Question 6

This prescription exhibits what type of astigmatism? +2.50 -3.50 X 180

Answer 6

Mixed astigmatism

Question 7

This prescription exhibits what type of astigmatism? -2.50 -1.50 X 180

Answer 7

Compound myopic astigmatism

Question 8

This prescription exhibits what type of astigmatism? +2.50 -1.50 X 180

Answer 8

Compound hyperopic astigmatism

Question 9

This prescription exhibits what type of astigmatism? +2.50 +1.50 X 180

Answer 9

Compound hyperopic astigmatism

Question 10

Transposing a prescription changes the value of the lens and makes it more accurate. (True/False)

Answer 10

False

Question 11

In placing the following prescription on an optical lens cross, please identify the powers in the principle meridians. -2.50 -1.00 X 180.

Answer 11

-2.50 @ 180 / -3.50 @ 090

Question 12

Irregular astigmatism is the condition whereby ___.

Answer 12

The principle meridians are not at right angles to one another and are better corrected with the use of contact lenses.

Question 13

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 180 / -2.50 @ 180 / -4.00 @ 090

Answer 13

With the rule astigmatism

Question 14

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 135 / -2.50 @ 135 / -4.00 @ 045

Answer 14

Oblique astigmatism

Question 15

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 090 / -2.50 @ 090 / -4.00 @ 180

Answer 15

Against the rule astigmatism

Question 16

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 180 / -2.50 @ 180 / -4.00 @ 090

Answer 16

Corneal astigmatism

Question 17

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 180 / -2.50 @ 180 / -2.50 @ 090

Answer 17

Lenticular astigmatism

Question 18

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 180 / -2.50 @ 180 / -4.00 @ 090

Answer 18

Regular astigmatism

Question 19

This prescription exhibits what type of astigmatism?
Rx: -2.50 -1.50 X 180 / -2.50 @ 180 / -4.00 @ 060

Answer 19

Irregular astigmatism

Question 20

Based upon the following prescription what information can we determine about it?
Rx: -2.50 -1.50 X 180 / -2.50 @ 180 / -4.00 @ 090
(List)

Answer 20

Regular astigmatism / compound myopic astigmatism / with the rule astigmatism / corneal astigmatism

Question 21

Based upon the following prescription what information can we determine about it?
Rx: +2.50 -1.50 X 180 / +2.50 @ 180 / +1.00 @ 090

Answer 21

Regular astigmatism / compound hyperopic astigmatism / against the rule astigmatism / corneal astigmatism