Ophthalmology: Visual Physiology, Cues and Illusions ("Not Testable") Flashcards
Cranial Nerves involved with the eye
CN 2 = sight
CN 3/4/6 = movement
CN 5 = cornea sensation and iris
CN 7 = lid closure and lacrimal gland
Ganglion cells respect _____ visual field
Horizontal (think optic n)
+Gz lead to…
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*
-Gz lead to….
increased blood congestion
Red-out at -3 to -8Gz
Acquired red green deficiency is caused by:
- Mercury
- Organic Solvents
- Toluene
- Styrene
- Alcohol
- n-hexane
- Carbon Disulfide
- Perchlorethylene
- Meds
- Brain Tumors
Acquired blue deficiency is caused by…
- Cataract
- Glaucoma
- Retinopathy
- Meds
- Infection
Scotopic vision
Vision of the eye under low-light levels
RODS
Photopic vision
Vision of the eye under well-lit conditions (allowing color perception)
CONES
Mesopic vision
Vision at low light dusk/dawn
RODS and CONES
How long does dark adaptation take
30 minutes (80%)
True/False
Bright sunlight exposure reduces night vision up to 48 hours
True
Avoid beach prior to night missions
Rhodopsin
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*
____ light can speed night adaptation
Red light
True/False
There is a difference in dark adaptation for smokers
False (no difference)
_____ gives best dim-light detection
“Off-gazing” (rods off center)
Night Blindness Etiology
aka Nyctalopia
Vit A & Zinc deficiency (reduced)
Retinitis Pigmentosa (rod dystrophy)
Red light preserves _____ while Green/Low White light perserves _____.
Red light perserves night ROD vision
Green/Low White light perserves CONE vision (central)
What 3 visual factors give stereovision in the brain
Stereopsis (retinal overlap disparity - requires two aligned eyes with good vision)
Ocular convergence (biological “range-finder”)
Accommodation (“focus” to see object)
Stereopsis is only effective to ____ m.
200m
Navy standard for stereopsis
40 arcsec
Best acuity with a static target is as the ______
Fovea (densest cones)
“Motion sensor” of the eye
Peripheral retina (very sensitive to movement)
