Ch 2. Pt 2

Question 1

Use monochromatic light to determine threshold at different wavelengths

Answer 1

threshold for light is lowest in the middle of spectrum

Question 2

wats to mesure visual acuity

Answer 2

Interdot separation
Snellen eye chart
Lea test (children)
Landolt rings
Tumbling E

Question 3

Purkinje Shift

Answer 3

rods more sentive then cones (endency for the peak luminance sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels.) Reds get darker

Question 4

Dark adaption

Answer 4

ability to see is poor at first then it studies out and at 5 minutes starts getting progressively better as rods take over

Question 5

Scotopic Vision

Answer 5

• rod dominated
• sensitive in dim light
• poor visual acuity
• no colour sensation

Question 6

Photopic Vision

Answer 6

• cone dominated
• insensitive in dim light
• good visual acuity
• good colour vision

Question 7

Duplex retnia

Answer 7

-refers to the fact that the eye contains two sets of different photosensitive receptors - the rods and the cones
-increases the dynamic range over which the eye can function
-is consistent with
.dark adaptation
.purkinje shift
.visual acuity
.visual sensitivity

Question 8

Ganglion convergence

Answer 8

• More convergence for rods
• More convergence in peripheral retina
• More convergence = greater sensitivity to light
• More convergence = Lower acuity

Question 9

receptive field

Answer 9

area of the retina which when stimulated influences the activity of the cell (excititory=on centre, inhibitory=off centre)

Question 10

lateral inhibition

Answer 10

Three lightness perception phenomena explained by lateral inhibition (or edge enhancement)

• The Hermann Grid: Seeing spots at an intersection
• Mach Bands: Seeing borders more sharply
• Simultaneous Contrast: Seeing areas of different brightness due to adjacent areas

Question 11

Diabetic Retinopathy

Answer 11

Damage to retinal blood vessels causes leakage, neovascularisation and potentially, retinal detachment

Question 12

Macular Degeneration

Answer 12

Disease of old age
Central part of visual field deteriorates
Results in loss of central vision (macula = fovea)

Question 13

Retinitis Pigmentosa

Answer 13

Hereditary retinal degeneration
Starts in retinal periphery
Initial symptom night-blindness and loss of
 peripheral vision, then tunnel vision, then
 total blindness

Question 14

Glaucoma

Answer 14

Eye disease usually associated with increase in intraocular pressure
Untreated can lead to blindness
Several different forms