Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Perception Block 9 > Duplex Retina 2 > Flashcards

Duplex Retina 2 Flashcards

1
Q

A patient whose retina contains only rods views the following four patches of monochromatic light: 440, 510, 555, and 565nm. Each patch emits 20 quantal absorptions. Which is brightest

A

510nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Your patient, a rod monochromat, has asked for advice regarding tinted lenses. You should advise a darkly tinted lens of which color?

A

Red

PI=0 at 650nm. Want the smallest PI

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A patient has degenerative disease that has destroyed her cones. The expected VA for this patient is closest to

A

20/200

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Under daylight conditions, a red and green surface looks equally bright. Compared to the green surface, the red surface most likely emits

A

More energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which of the following classes of cones contributes least to the photopic spectral sensitivity curve

A

S cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Assume that the absorption of 10 quanta of 510nm by an eye that contains only rods results in vision. If the wavelength were 450nm, how many quanta would need to be absorbed to produce vision

A

> 10 quanta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Under scotopic conditions, a blue and yellow flower appear equally bright. Under photopic conditions, which flower will most likely appear brightest

A

Yellow flower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When foveal fixated by a person with trichromatic vision, a small target (o.5 degrees) of which of the following wavelengths will be least visible

A

430nm

No blue cones from 0.3-0.4 degrees, no rods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Photopic and scotopic thresholds are most similar to each other for which wavelength

A

650nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Visual systems ability to adapt to the changes in the illumination levels

A

Light adaptation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Light adaptation may be studied with an ________procedure

A

Increment threshold

Stimulus only seen when brighter than background

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is threshold determined for light adaptation

A

Determined for a flash of light-an increment-that is presented on a background of a given intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

After the threshold has been determined for the light adaptation

A

The background intensity is increased and the threshold measurement is repeated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Weber fraction for scotopic vision

A

0.14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

M=0 on the scotopic light adaptation curve

A

Dark light, neural noise internal to retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

M=1/2 on the scotopic light adaptation curve

A

Square root law: this region is limited only quantal fluctuation of the background, and has a slope of 0.5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

M=1 on the scotopic light adaptation curve

A

Weber law: the slope of the curve is equal to about 1. The ratio of increment intensity to background intentist remains constant, and covers ~4 log units range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

M=infinity on the scoptopic light adaptation curve

A

Rod saturation: the slope increases rapidly becomes infinity. The rod system starts to beceom unable to detect the stimulus with the high background luminance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

In terms of contrast, which is more sensitive, scotopic system or photopic system

A

Photopic system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Weber fraction for scotopic vision

A

0.14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Weber fraction for photopic vision

A

0.015

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

The smaller then Weber fraction

A

The more sensitive it is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Although the photopic systme is more sensitive (10x) to CONTRAST than the scoptopic system…

A

It’s absolute sensitivity is less

24
Q

Ability to resolve: photopic vision

A

Superior
1 log unit difference
20/20

25
Q

Ability to resolve: scotopic vision

A

Inferior 20/200

26
Q

Contrast sensitivity: photopic

A

10X better

Weber=0.015

27
Q

Contrast sensitivity: scotopic

A

Poor

Weber=0.14

28
Q

Ability to detect: photopic

A

Inferior

29
Q

Ability to detect: scoptopic

A

Superior

3 log units photochromatic interval

30
Q

Why the difference between visual resolution an visual sensitivity for photopic and scotopic vision

A

Scotopic is absolute more sensitive.

Photopic is more sensitive for contrast (threshold). Resolution

31
Q

Difference between visual resolution and visual sensitivity

A

Due to the manner in which the rods and cones are connected to the post-receptoral elements of the retina

32
Q

Rods are connected in such a manner as to _______ information over space. This produces great sensitivity, but poor resolution

A

Sum up

33
Q

Cones manifest connections that _____________ at the expense of sensitivity

A

Maximize visual resolution

34
Q

How many ganglion per rod

A

10-15

35
Q

How many ganglion per cone

A

1:5, or 1:1 in the fovea

36
Q

Many more rods communicate with a ganglion cell than is the case for cones. This illustrates that the scotopic system ______ information _______ to a greater extent than the photopic system, it manifests greater ___________

A

Sums up
Over space
Spatial summation

37
Q

When two spots of light are shown on rods, it does not signal the presence of two lights, this information is lost because of

A

Spatial summation

38
Q

This system has excellent sensitivity, yet poor spatial resolution

A

Scotopic system

39
Q

Under ______ conditions, the two ganglion cells each reach threshold and signal the presence of a stimulus; sonsequntly, two stimuli are seen

A

Photopic

40
Q

Excellent spatial summation

A

Scotopic system

41
Q

Excellent spatial resolution

A

Photopic system

42
Q

Scotopic and photopic vision also demonstrate significant difference in their

A

Temporal (time-related) properties

43
Q

Scotopic conditions:two lights below threshold, separates by an interval greater than 100ms

A

No stimulus seen

44
Q

Scotopic vision: 2 lights shown under threshold, but within 100ms

A

They will be summed up to reach threshold, stimulus seen, but only one flash of light

45
Q

Scotopic vision: two lights shown that go beyond threshold and within the interval period

A

Still just one flash seen. The scotopic systems high degree of temporal summation limits its availability to resolve distinct temporal events

46
Q

Scotopic vision: when two suprathreshold pulses are separated by greater than the interval period (greater than 100mn)

A

Two flashes seen

47
Q

Which has a shorter period of temporal summation

A

Photopic, 10ms

48
Q

Photopic: when a light shown at a longer interval than 10s and neither reach threshold

A

No flash seen

49
Q

Photopic: two lights shown within the 10s, but do not reach threshold

A

One flash seen

50
Q

Photopic: When two lights are shown that both reach above the threshold, but in two different time intervals

A

See two flashes

51
Q

Threshold contrast, under photopic conditions, is closest to

A

0.010

52
Q

To optimize the rod-cone break of the dark adaptation curve for clinical testing, the stimulus should be

A

5.0 degrees in diameter and green

53
Q

Consider the region of the photopic light adaptation curve that follows Weber law. As the background intensity decreases, contrast

A

Remains constant

Ratio must remains close to one

54
Q

The percentage of rhodopsin that is bleached at rod saturation is closest to

A

15%

55
Q

The photochromatic interval is expected to be smalles for a

A

Centrally fixed 0.5 degree yellow target

56
Q

An abnormal dark adaptation curve may be indicative of

A

ARMD and RP

Perception Block 9 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions