Duplex retina

Question 1

Pupil size accounts for

Answer 1

1 log unit

Question 2

Scotopic vision

Answer 2

Low levels of light, rod sensitive

Question 3

Photopic vision

Answer 3

Bright levels of light, cone sensitive

Question 4

Mesopic vision

Answer 4

Intermediate light levels, both cones and rods operate

Question 5

Peak density of rods

Answer 5

150,000 at 20 degrees from fovea

Question 6

Peak density of cones

Answer 6

115,000-225,000 at foveal center with the absence of S-cones

Question 7

Peak density of s-cones

Answer 7

2,000 at 0.5 degrees from foveal center

Question 8

How much rhodopsin in each eye

Answer 8

10^15

Question 9

Retinal

Answer 9

Chromophore part of rhodopsin made from vitamin A

Question 10

Opsin

Answer 10

Protein part of rhodopsin

Question 11

Bleached state

Answer 11

When molecule of rhodopsin absorbs a photon of light, unable to absorb another photon

Question 12

What is the half life of rhodopsin

Answer 12

5 minutes

Question 13

Rhodopsin absorbs at

Answer 13

507 nm

Question 14

Principle of univariance

Answer 14

Ability to match the response of a photoreceptor to a lower intensity light at a preferred wavelength to that of a higher intensity light at a less efficient wavelength

Question 15

Detection threshold

Answer 15

The dimmest light stimulus of any given wavelength that a subject can detect

Question 16

L-cone pigment and peak absorption

Answer 16

Erythrolabe
565 nm
Red

Question 17

M-cone pigment and peak absorption

Answer 17

Chlorolabe
535 nm
Green

Question 18

S-cone pigment and peak absorption

Answer 18

Cyanolabe
430 nm
Blue

Question 19

Photopic peak absorption

Answer 19

555nm

S-cones make no contribution

Question 20

Photochromatic interval

Answer 20

Difference in sensitivity between the scotopic and photopic systems for a given wavelength

Question 21

Purkinje shift

Answer 21

Shift in relative brightness of suprathreshold stimuli as peak sensitivity moves from 555 to 507nm

Question 22

Half-life of cones

Answer 22

1.5 minutes

Question 23

Dark adaptation

Answer 23

Recovery of visual sensitivity over time following exposure to a bright light

Question 24

When is the rod-cone break the steepest?

Answer 24

At wavelengths with large photochromatic intervals

Question 25

Rod monochromacy

Answer 25

Condition characterized by a near absence of cones in the retina

Question 26

Retinal densitometry

Answer 26

Measures the amount of bleached rhodopsin in percentages

Question 27

Dowling-rushton equation

Answer 27

log(threshold at given time/threshold after complete da) = 20 for rods or 3 for cones * proportion of bleached photopigment

Question 28

Light adaptation

Answer 28

Process of the visual system adjusting its performance to the ambient level of illumination when going from dark to light

Question 29

Increment threshold procedure

Answer 29

Used to measure light adaptation, must detect a faint light stimulus against a uniform background as it grows progressively lighter

Question 30

Increment

Answer 30

Difference between background luminance and stimulus luminance

Question 31

Section one of light adaptation function

Answer 31

Dark light Sensitivity is limited by neural nose inherent in the visual system Theoretical

Question 32

Neural noise

Answer 32

Visual light phenomena when in a completely dark room or with eyes closed

Question 33

Section two of light adaptation function

Answer 33

De-Vries rose law | Sensitivity is limited by quantal fluctuations inherent in the background light source

Question 34

De-Vries rose law

Answer 34

Increase in threshold is equal to the square root of background intensity

Question 35

Section three of light adaptation function

Answer 35

Weber's law | Relative sensitivity stays constant while absolute sensitivity decreases

Question 36

Weber's law

Answer 36

Increase in background intensity leads to a constant ratio of increment intensity to background

Question 37

Section 4 of light adaptation function

Answer 37

Rod saturation Rods unable to signal the presence of a stimulus even with infinite increase in brightness At 10% bleached rhodopsin

Question 38

Section 5 of light adaptation function

Answer 38

Photopic section | Follows weber's law with an increased contrast sensitivity

Question 39

Absolute sensitivity

Answer 39

How well a subject can go from seeing nothing to seeing something Scotopic

Question 40

Relative sensitivity

Answer 40

When a subject can detect a target against the background | Photopic

Question 41

Static perimetry

Answer 41

Computes the increment thresholds at different locations of the visual field holding the background luminance constant

Question 42

Good spatial summation

Answer 42

Scotopic

Question 43

Poor spatial resolution

Answer 43

Scotopic

Question 44

Good resolving capacity

Answer 44

Photopic

Question 45

Poor spatial summation

Answer 45

Photopic

Question 46

Poor sensitivity to target detection in dim light

Answer 46

Photopic

Question 47

Larger receptive fields

Answer 47

Scotopic

Question 48

Scotopic system critical period

Answer 48

100ms

Question 49

Photopic system critical period

Answer 49

10ms

Question 50

Ricco's law

Answer 50

When the threshold number of quanta are within 10 minutes of arc, there is complete spatial summation and stimulus is detected Stimulus intensity times area equals constant

Question 51

Bloch's law

Answer 51

Within the critical duration, the total number of quanta required to reach threshold remains constant for different flash durations If flash duration exceeds critical, total quanta required increases Stimulus intensity times duration equals constant

Question 52

Relative luminous efficiency

Answer 52

The apparent brightness of the light to an individual

Question 53

Stiles Crawford Effect 1

Answer 53

Directional sensitivity of cones Light that enters straight through the center of the pupil is more effective in cone stimulation than if it enters peripherally

Question 54

Intraocular scatter

Answer 54

Scattered light that strikes the cones at large oblique angles Minimized due to SCE1

Question 55

Duration of dark adaptation for experiment

Answer 55

At least 40 minutes

Question 56

Where in visual field should test flash be presented?

Answer 56

20 degrees temporal to the fovea due to peak rod density

Question 57

Size of the test flash?

Answer 57

10 arc minutes in diameter due to Ricco's law

Question 58

Duration of test flash?

Answer 58

1 millisecond due to bloch's law

Question 59

Stimulus wavelength for experiement?

Answer 59

510 nm due to scotopic sensitivity curve