Ophthalmology: Visual Physiology, Cues and Illusions ("Not Testable")

Question 1

Cranial Nerves involved with the eye

Answer 1

CN 2 = sight

CN 3/4/6 = movement

CN 5 = cornea sensation and iris

CN 7 = lid closure and lacrimal gland

Question 2

Ganglion cells respect _____ visual field

Answer 2

Horizontal (think optic n)

Question 3

+Gz lead to…

Answer 3

reduced perfusion of choroid/retinal vessels

• Grey-out at approx 4Gz (loss of peripheral color vision)*
• Black-out at approx 5-9Gz**
• *Variable delta between LOV and LOC*

Question 4

-Gz lead to….

Answer 4

increased blood congestion

Red-out at -3 to -8Gz

Question 5

Acquired red green deficiency is caused by:

Answer 5

• Mercury
• Organic Solvents
• Toluene
• Styrene
• Alcohol
• n-hexane
• Carbon Disulfide
• Perchlorethylene
• Meds
• Brain Tumors

Question 6

Acquired blue deficiency is caused by…

Answer 6

• Cataract
• Glaucoma
• Retinopathy
• Meds
• Infection

Question 7

Scotopic vision

Answer 7

Vision of the eye under low-light levels

RODS

Question 8

Photopic vision

Answer 8

Vision of the eye under well-lit conditions (allowing color perception)

CONES

Question 9

Mesopic vision

Answer 9

Vision at low light dusk/dawn

RODS and CONES

Question 10

How long does dark adaptation take

Answer 10

30 minutes (80%)

Question 11

True/False

Bright sunlight exposure reduces night vision up to 48 hours

Answer 11

True

Avoid beach prior to night missions

Question 12

Rhodopsin

Answer 12

Biological pigment found in RODS of the retina (extremely sensitive to light and enables vision in low-light conditions)

• When rhodopsin is exposed to light it photobleaches*
• Regenerates with Vit A and Carrots/Leafy greens*

Question 13

____ light can speed night adaptation

Answer 13

Red light

Question 14

True/False

There is a difference in dark adaptation for smokers

Answer 14

False (no difference)

Question 15

_____ gives best dim-light detection

Answer 15

“Off-gazing” (rods off center)

Question 16

Night Blindness Etiology

Answer 16

aka Nyctalopia

Vit A & Zinc deficiency (reduced)

Retinitis Pigmentosa (rod dystrophy)

Question 17

Red light preserves _____ while Green/Low White light perserves _____.

Answer 17

Red light perserves night ROD vision

Green/Low White light perserves CONE vision (central)

Question 18

What 3 visual factors give stereovision in the brain

Answer 18

Stereopsis (retinal overlap disparity - requires two aligned eyes with good vision)

Ocular convergence (biological “range-finder”)

Accommodation (“focus” to see object)

Question 19

Stereopsis is only effective to ____ m.

Answer 19

200m

Question 20

Navy standard for stereopsis

Answer 20

40 arcsec

Question 21

Best acuity with a static target is as the ______

Answer 21

Fovea (densest cones)

Question 22

“Motion sensor” of the eye

Answer 22

Peripheral retina (very sensitive to movement)