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Vision science > Duplex retina > Flashcards

Duplex retina Flashcards

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Biology 101 flashcards
1
Q

Pupil size accounts for

A

1 log unit

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2
Q

Scotopic vision

A

Low levels of light, rod sensitive

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3
Q

Photopic vision

A

Bright levels of light, cone sensitive

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4
Q

Mesopic vision

A

Intermediate light levels, both cones and rods operate

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5
Q

Peak density of rods

A

150,000 at 20 degrees from fovea

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6
Q

Peak density of cones

A

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

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7
Q

Peak density of s-cones

A

2,000 at 0.5 degrees from foveal center

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8
Q

How much rhodopsin in each eye

A

10^15

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9
Q

Retinal

A

Chromophore part of rhodopsin made from vitamin A

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10
Q

Opsin

A

Protein part of rhodopsin

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11
Q

Bleached state

A

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

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12
Q

What is the half life of rhodopsin

A

5 minutes

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13
Q

Rhodopsin absorbs at

A

507 nm

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14
Q

Principle of univariance

A

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

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15
Q

Detection threshold

A

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

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16
Q

L-cone pigment and peak absorption

A

Erythrolabe
565 nm
Red

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17
Q

M-cone pigment and peak absorption

A

Chlorolabe
535 nm
Green

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18
Q

S-cone pigment and peak absorption

A

Cyanolabe
430 nm
Blue

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19
Q

Photopic peak absorption

A

555nm

S-cones make no contribution

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20
Q

Photochromatic interval

A

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

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21
Q

Purkinje shift

A

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

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22
Q

Half-life of cones

A

1.5 minutes

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23
Q

Dark adaptation

A

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

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24
Q

When is the rod-cone break the steepest?

A

At wavelengths with large photochromatic intervals

25
Q

Rod monochromacy

A

Condition characterized by a near absence of cones in the retina

26
Q

Retinal densitometry

A

Measures the amount of bleached rhodopsin in percentages

27
Q

Dowling-rushton equation

A

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

28
Q

Light adaptation

A

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

29
Q

Increment threshold procedure

A

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

30
Q

Increment

A

Difference between background luminance and stimulus luminance

31
Q

Section one of light adaptation function

A

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

32
Q

Neural noise

A

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

33
Q

Section two of light adaptation function

A

De-Vries rose law

Sensitivity is limited by quantal fluctuations inherent in the background light source

34
Q

De-Vries rose law

A

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

35
Q

Section three of light adaptation function

A

Weber’s law

Relative sensitivity stays constant while absolute sensitivity decreases

36
Q

Weber’s law

A

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

37
Q

Section 4 of light adaptation function

A

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

38
Q

Section 5 of light adaptation function

A

Photopic section

Follows weber’s law with an increased contrast sensitivity

39
Q

Absolute sensitivity

A

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

40
Q

Relative sensitivity

A

When a subject can detect a target against the background

Photopic

41
Q

Static perimetry

A

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

42
Q

Good spatial summation

A

Scotopic

43
Q

Poor spatial resolution

A

Scotopic

44
Q

Good resolving capacity

A

Photopic

45
Q

Poor spatial summation

A

Photopic

46
Q

Poor sensitivity to target detection in dim light

A

Photopic

47
Q

Larger receptive fields

A

Scotopic

48
Q

Scotopic system critical period

A

100ms

49
Q

Photopic system critical period

A

10ms

50
Q

Ricco’s law

A

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

51
Q

Bloch’s law

A

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

52
Q

Relative luminous efficiency

A

The apparent brightness of the light to an individual

53
Q

Stiles Crawford Effect 1

A

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

54
Q

Intraocular scatter

A

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

55
Q

Duration of dark adaptation for experiment

A

At least 40 minutes

56
Q

Where in visual field should test flash be presented?

A

20 degrees temporal to the fovea due to peak rod density

57
Q

Size of the test flash?

A

10 arc minutes in diameter due to Ricco’s law

58
Q

Duration of test flash?

A

1 millisecond due to bloch’s law

59
Q

Stimulus wavelength for experiement?

A

510 nm due to scotopic sensitivity curve

Vision science (13 decks)

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