Visual Acuity And Emmetropia II

Question 1

The forefathers of VA

Answer 1

Francisco Cornelius donders and Herman snellen

Question 2

Sharpness of vision can be expressed in terms of the ______ of letter size to viewing distance

Answer 2

Ratio

Question 3

Who determined we can see up to 1 arcmin

Answer 3

Robert Hooke

Question 4

How is VA calculated

Answer 4

Reciprocal of minimum angle

Question 5

What can recognize an optotype when its detail subtended 1 arcmin

Answer 5

The vision of the standard eye

Question 6

Difference between minimum angle of resolution and magnification requirement

Answer 6

Nothing, essential the same thing

Question 7

Optical aspects of vision, resolution

Answer 7

Minimum angle of resolution MAR

Question 8

Magnification required to compensate for reduce vision; actual measurement

Answer 8

Magnification requirement MAR

Question 9

What is the standard of optotype

Answer 9

1 arcmin spearation between black and white

Question 10

Optotype detail size

Answer 10

h=6m x (tan1’)=1.746mm

Question 11

Overall character size

Answer 11

D=6m=20ft

5 x 1.746mm=8.73mm

Question 12

Why 6m or 20ft distance?

Answer 12

• large enough to approximate the optical infinity for the optical system of the human eye
• vergence is negligible
• accommodation is relaxed

Question 13

What is optical infinity

Answer 13

6m

Question 14

Eye chart used in testing near VA

Answer 14

Jager Chart

Question 15

Why is jager chart not the best

Answer 15

Distance is variable in this type of chart

Question 16

To determine VA

Answer 16

We find the smallest optotype that they can read