lecture 3: the duplex retina

A patient whose retina contains only rods (i.e., a rod monochromat) views the following four patches of monochromatic light: 440, 510, 555, and 565 nm. Each patch emits 20 quanta absorptions. Which is brightest?

510 nm

Threshold contrast, under photopic conditions, is closest to:

0.010

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

5.0 degrees in diameter and green

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

remains constant

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

10 quanta

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

red

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

the yellow flower

What percentage of cone photopigment has regenerated 3.0 minutes following a 100% bleaching?

75%

When foveally fixated by a person with trichromatic vision, a small target (0.5 degrees) of which of the following wavelengths will be least visible?

430 nm

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

20/200

Assuming visual fields are obtained under lighting conditions that fall in the Weber region, a reduction in retinal illumination caused by nuclear sclerosis is expected to result in visual field thresholds that are:

unchanged

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

more energy

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

650 nm

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

15%

The photochromatic interval is expected to be smallest for a:

centrally fixated 0.5 degree yellow target

Sensitivity regulation is most associated with the portion of the light adaptation curve that has a slope of:

1

A patient has a condition that results in the total elimination of his SWS cones without affecting any other retinal structure. The patient's expected visual acuity is:

20/20

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

s-cones

An abnormal dark adaptation curve may be indicative of:

c) both

For points that fall on an isopter, visual sensitivity is:

the same

If the fovea is destroyed by disease, the expected visual acuity is closest to:

20/200