Visual Acuity

Question 1

What is the definition of legal blindness?

Answer 1

Best-corrected visual acuity of 20/200 or less in the better eye, or a visual field of no more than 20 degrees

Question 2

Amblyopia

Answer 2

Lazy eye. Neurological development disorder that present with deficits in spatio-temporal vision processing.

Question 3

20/20 vision assumes how many minutes of arc?

Answer 3

1 minute

Question 4

What would “perfect” vision actually be recorded in snellen and minutes of arc?

Answer 4

20/10 and 30 seconds of arc.

Question 5

What is the optimal pupil size?

Answer 5

3mm

Question 6

Large pupils experience reduced ________ so resolution is limited by _______

Answer 6

Reduced Diffraction, Limited by Aberrations

Question 7

Small pupils experience reduced _________ so resolution is limited by _________

Answer 7

Reduced Aberrations, Limited by Diffraction

Question 8

Where is the concentration of rods in the eye greatest?

Answer 8

15 degrees from the fovea

Question 9

Where is the concentration of cones in the eye the greatest?

Answer 9

on the fovea

Question 10

How fast do cones regenerate photopigments?

Answer 10

5 - 10 minutes

Question 11

How fast do rods regenerate photopigments?

Answer 11

30-50 minutes

Question 12

What is the current standard for VA charts?

Answer 12

LogMAR spacing, Sloan optotypes, at a distance of 4m

Question 13

What is the formula for optotype size in relation to test distance?

Answer 13

Height (mm) = tan (min of arc/60) x distance (mm)

Question 14

For Snellen, how many letters need to be read correctly in order to record that baseline?

Answer 14

3 or more

Question 15

For LogMAR charts, when do you stop recording a patient’s score?

Answer 15

If he/she misses 4 out of 5 letter on a given line

Question 16

What is a Landolt C VA chart?

Answer 16

Has a series of rings with a 1 min arc gap. Guess position of gap

Question 17

When is Tumbling E VA chart used?

Answer 17

Sometimes with children, illiterate patients

Question 18

How do you convert from logMAR to snellen?

Answer 18

MAR = 10 ^(logMAR value)

Question 19

How do you convert from snellen to logMAR?

Answer 19

20/MAR = x then take the log10 of MAR

Question 20

True/False. Patients typically do better on logMAR when compared to snellen.

Answer 20

True

Question 21

What’s on both sides of an ICO Near Vision Card?

Answer 21

One side = logMAR

Other side = Lea symbols

Question 22

What’s on both sides of a Lighthouse Near Vision Card?

Answer 22

One side = Words

Other side = Numbers

Question 23

What’s on both sides of a Runge Near Vision Card?

Answer 23

One side = logMAR moving horizontally

Other side = True snellen

Question 24

How do you record low vision?

Answer 24

M-units: 20/20 equivalent @ 40 cms is 0.4M

Question 25

Define Amplitude of Accomodation

Answer 25

Maximum amount a patient can accommodate

Question 26

How do you record the Push-Up Method?

Answer 26

Measure the distance of “sustained blur” and take 100 / distance (cms).

Question 27

What is Hofstetter’s Formula?

Answer 27

For Push-Up Method: Minimum Amp = 15 - (Age/4)

Question 28

For 3-year-olds, what Lea card do you use?

Answer 28

10/20

Question 29

For 4-year-olds and beyond, what Lea card do you use?

Answer 29

10/16

Question 30

Ametropia

Answer 30

Refractive error

Question 31

Emmetropia

Answer 31

Zero refractive error

Question 32

Myopia is corrected with + or - lenses?

Answer 32

-

Question 33

Hyperopia is corrected with + or - lenses?

Answer 33

+

Question 34

Define Presbyopia

Answer 34

Cannot resolve detail at close distances