Principles Of And Problems With Vision

Question 1

RODS AND CONES

Answer 1

Cones=Day

Rodes=night

Question 2

DAY BLIND SPOT

Answer 2

Compensated for via binocular vision. 5.5-7.5 degrees and is located 15 degrees from the fovea, originating where the optic nerve attaches to the retina.

Question 3

TYPES OF VISION

Answer 3

Photopic:

Question 4

TYPES OF VISION

Answer 4

Photopic: Day vision
Mesopic: Experienced at dawn, dusk, and full moonlight
Scotopic: Night vision, partial moonlight and starlight conditions

Question 5

NIGHT BLIND SPOT

Answer 5

Occurs when the fovea becomes inactive in low light conditions and involves an area 5-10 degrees wide in the center of the visual field. Peripheral vision is used to overcome the effects of Scotopic vision.

Question 6

VISUAL DEFICIENCIES

Answer 6

Myopia=nearsightedness
Night Myopia=night blue and green wavelengths
Hyperopia=farsightedness
Astigmatism=inability to focus different meridians simultaneously: unequal curvature of the cornea or eye lens.

Question 7

DARK ADAPTATION

Answer 7

30-45min.
Exposure of 1sec or longer to high intensity light or repeated exposure, re-adaption time can take several to 45min.
Exposure to bright sunlight for 2-5hrs decreases visual sensitivity for up to 5 hrs.

Question 8

NIGHT VISION/DARK ADAPTATION TIME

Answer 8

30-45min. Occurs due to the build-up of rhodopsin. When fully adapted rod cells become 10,000x more sensitive to light. With fully dilated pupils 100,000x more sensitive.