Duplex Retina

Question 1

What makes it possible for the human eye to see something very bright and very feeble in the night sky?

Answer 1

Pupil changing diameter in response to light

Question 2

Consider a white page with luminance of 100 nits. Compute the reitnal luminance for a 9mm diameter pupil. (Now what about a pupil with 2 diameter pupil)

Answer 2

Pir^2
(3.14)(4.5)^2=63.62
td= (100)(63.62)= 6,362 td

(3.14)(1^2)= 3.14mm^2
td= (100)(3.14)= 314 td

Question 3

Pupillary diameter account for about 10% of light adaptation, what does the rest?

Answer 3

Rods and cones

Question 4

Scotopic vision distinctions:

Answer 4

REPN scotopic vision:
RODS
Exquisite sensitivity to very dim lights
Poor VA (20/200 vision)
NO color discrimination

Question 5

Photopic vision

Answer 5

PECC (imPECCable) VA with photopic
Poor sensitivity to dim lights
Excellent VA
Color discrimination
CONES

Question 6

The existence of 2 classes of photoreceptors, each operating under diff lighting conditions is known as:

Answer 6

Duplex Retina

Question 7

The photopigment ________ is contained within the discs of the rod’s outer segment.

Answer 7

Rhodopsin

captures light and contributes to our sensitivity to dim lighting

Question 8

Quanta of ____nm have the highest probability of absorption.

Answer 8

507nm

Question 9

Once a quantum of light is absorbed, all info regarding its wavelength is lost, this is referred to as:

Answer 9

Univariance

Question 10

A molecule of rhodopsin becomes ______ when it absorbs light.

Answer 10

bleached

Question 11

The absorption of _____________ of light is required to bleach a molecule of rhodopsin.

Answer 11

one quantum

Question 12

The half life of rhodopsin regeneration is _________..

Answer 12

5 minutes (50% of bleached rhodopsin molecules will recover in 5 minutes)

Question 13

3 cone photopigment colors and nm for each

Answer 13

Blue: 426nm
Green: 530nm
Red: 557nm

Question 14

Which cones make little contribution to spectral sensitivity?

Answer 14

s-cones

Question 15

The difference in sensitivity between scotopic and photopic systems, for a given wavelength, is referred to as the:

Answer 15

photochromatic interval.

Question 16

The scotopic is more sensitive than the photopic system in all wavelengths except what?

Answer 16

red region

Question 17

T/F: Photochromatic intervals increase with retinal eccentricity

Answer 17

True

Question 18

As lighting conditions change from scotopic to photopic, the wavelength to which we are most sensitive increases from ___ to ___.

Answer 18

507 to 555nm

Question 19

The relative increase in the brightness of longer wavelength stimuli as lighting conditions change from scotopic to photopic.

Answer 19

Purkinje shift

Question 20

Human retina contains approx _____ rods and ______ cones

Answer 20

120 million rods

6 million cones

Question 21

After _____ minutes in the dark the eye is ________ times more light sensitive.

Answer 21

35 min

100,000 times

Question 22

T/F: Rods recover faster than cones

Answer 22

False, cones recover faster than rods

Question 23

The lower the threshold the _______ the sensitivity.

Answer 23

higher

threshold is inverse of sensitivity

Question 24

____________ is the difference between the cone plateau (min photopic threshold) and the rod plateau (min scotopic threshold)

Answer 24

Photochromatic interval
(is ~3 log units)

Question 25

True/False: Rods are not more sensitive than cones for long wavelengths.

Answer 25

True

Question 26

Weber fraction for scotopic vision is what?.

Answer 26

~0.14

Question 27

Wener fraction for photopic vision is what?

Answer 27

~0.015

Question 28

T/F: Photopic system is more sensitive to contrast than scotopic, its absolute sensitivity is less.

Answer 28

True