Duplex Retina 2

Question 1

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

Answer 1

510nm

Question 2

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

Answer 2

Red

PI=0 at 650nm. Want the smallest PI

Question 3

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

Answer 3

20/200

Question 4

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

Answer 4

More energy

Question 5

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

Answer 5

S cones

Question 6

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

Answer 6

> 10 quanta

Question 7

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

Answer 7

Yellow flower

Question 8

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

Answer 8

430nm

No blue cones from 0.3-0.4 degrees, no rods

Question 9

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

Answer 9

650nm

Question 10

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

Answer 10

Light adaptation

Question 11

Light adaptation may be studied with an ________procedure

Answer 11

Increment threshold

Stimulus only seen when brighter than background

Question 12

How is threshold determined for light adaptation

Answer 12

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

Question 13

After the threshold has been determined for the light adaptation

Answer 13

The background intensity is increased and the threshold measurement is repeated

Question 14

Weber fraction for scotopic vision

Answer 14

0.14

Question 15

M=0 on the scotopic light adaptation curve

Answer 15

Dark light, neural noise internal to retina

Question 16

M=1/2 on the scotopic light adaptation curve

Answer 16

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

Question 17

M=1 on the scotopic light adaptation curve

Answer 17

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

Question 18

M=infinity on the scoptopic light adaptation curve

Answer 18

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

Question 19

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

Answer 19

Photopic system

Question 20

Weber fraction for scotopic vision

Answer 20

0.14

Question 21

Weber fraction for photopic vision

Answer 21

0.015

Question 22

The smaller then Weber fraction

Answer 22

The more sensitive it is

Question 23

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

Answer 23

It’s absolute sensitivity is less

Question 24

Ability to resolve: photopic vision

Answer 24

Superior
1 log unit difference
20/20

Question 25

Ability to resolve: scotopic vision

Answer 25

Inferior 20/200

Question 26

Contrast sensitivity: photopic

Answer 26

10X better | Weber=0.015

Question 27

Contrast sensitivity: scotopic

Answer 27

Poor | Weber=0.14

Question 28

Ability to detect: photopic

Answer 28

Inferior

Question 29

Ability to detect: scoptopic

Answer 29

Superior | 3 log units photochromatic interval

Question 30

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

Answer 30

Scotopic is absolute more sensitive. Photopic is more sensitive for contrast (threshold). Resolution

Question 31

Difference between visual resolution and visual sensitivity

Answer 31

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

Question 32

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

Answer 32

Sum up

Question 33

Cones manifest connections that _____________ at the expense of sensitivity

Answer 33

Maximize visual resolution

Question 34

How many ganglion per rod

Answer 34

10-15

Question 35

How many ganglion per cone

Answer 35

1:5, or 1:1 in the fovea

Question 36

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 ___________

Answer 36

Sums up Over space Spatial summation

Question 37

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

Answer 37

Spatial summation

Question 38

This system has excellent sensitivity, yet poor spatial resolution

Answer 38

Scotopic system

Question 39

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

Answer 39

Photopic

Question 40

Excellent spatial summation

Answer 40

Scotopic system

Question 41

Excellent spatial resolution

Answer 41

Photopic system

Question 42

Scotopic and photopic vision also demonstrate significant difference in their

Answer 42

Temporal (time-related) properties

Question 43

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

Answer 43

No stimulus seen

Question 44

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

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

Two flashes seen

Question 47

Which has a shorter period of temporal summation

Answer 47

Photopic, 10ms

Question 48

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

Answer 48

No flash seen

Question 49

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

Answer 49

One flash seen

Question 50

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

Answer 50

See two flashes

Question 51

Threshold contrast, under photopic conditions, is closest to

Answer 51

0.010

Question 52

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

Answer 52

5.0 degrees in diameter and green

Question 53

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

Answer 53

Remains constant Ratio must remains close to one

Question 54

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

Answer 54

15%

Question 55

The photochromatic interval is expected to be smalles for a

Answer 55

Centrally fixed 0.5 degree yellow target

Question 56

An abnormal dark adaptation curve may be indicative of

Answer 56

ARMD and RP