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B9 PERCEPTION > Duplex Retina > Flashcards

Flashcards in Duplex Retina Deck (28):
1

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

Pupil changing diameter in response to light

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)

Pi*r^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

3

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

Rods and cones

4

Scotopic vision distinctions:

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

5

Photopic vision

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

6

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

Duplex Retina

7

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

Rhodopsin
(captures light and contributes to our sensitivity to dim lighting)

8

Quanta of ____nm have the highest probability of absorption.

507nm

9

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

Univariance

10

A molecule of rhodopsin becomes ______ when it absorbs light.

bleached

11

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

one quantum

12

The half life of rhodopsin regeneration is _________..

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

13

3 cone photopigment colors and nm for each

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

14

Which cones make little contribution to spectral sensitivity?

s-cones

15

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

photochromatic interval.

16

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

red region

17

T/F: Photochromatic intervals increase with retinal eccentricity

True

18

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

507 to 555nm

19

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

Purkinje shift

20

Human retina contains approx _____ rods and ______ cones

120 million rods
6 million cones

21

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

35 min
100,000 times

22

T/F: Rods recover faster than cones

False, cones recover faster than rods

23

The lower the threshold the _______ the sensitivity.

higher
(threshold is inverse of sensitivity)

24

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

Photochromatic interval
(is ~3 log units)

25

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

True

26

Weber fraction for scotopic vision is what?.

~0.14

27

Wener fraction for photopic vision is what?

~0.015

28

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

True