Lecture 2 - Duplex Retina

Question 1

A source with which of the following color temperature will appear most red?

Answer 1

2000K

Question 2

The color temperature of an incandescent bulb is 3300K. This means that:

Answer 2

The bulb’s spectral distribution matches that of a blackbody radiator whose temperature is 3300K

Question 3

A neutral density filter transmits 50% of 450nm light that is incident upon it. If 40W of 550nm are incident on the filter, how many watts are transmitted?

Answer 3

20

Question 4

The least amount of distortion is present with sunglasses made with a:

Answer 4

Neutral-density filter

Question 5

Which of the following light sources has more energy concentration in the blue region of the spectrum?

Answer 5

LEDs

Question 6

What makes it possible for the human eye to see something very bright and something very feeble in the night sky?

Answer 6

The pupil, by changing its diameter in response to light, helps to control the amount of light that falls upon the retina (in sun, it gets smaller; in dark, it gets bigger)

Question 7

Consider a white page with a luminance of 100 nits. Compute the retinal illuminance for a 9-mm diameter pupil

Answer 7

td = (nits) x (pupil area in mm)
Pupil area = (pi)r^2 = (3.14)(4.5)^2 = 63.62 mm^2
td = (100)(63.62) = 6,362 td

Question 8

Consider a white page with a luminance of 100 nits. Compute the retinal illuminance for a 2-mm diameter pupil

Answer 8

td = (nits) x (pupil area in mm)
Pupil area = (pi)r^2 = (3.14)(1)^2 = 3.14 mm^2
td = (100)(3.14) = 314 td

Question 9

What is the ratio of retinal illuminations between a 9-mm pupil and a 2-mm pupil?

Answer 9

20:1 (about equal to 1.3 log units = 13dB)

Question 10

How can the eye adjust to a 10-log unit range of retinal luminance if the pupil only accounts for 1.3 log units at max?

Answer 10

About 10% is how much the pupil has an effect for your retinal luminance

Question 11

Since pupillary diameter only accounts for about 10% of retinal illuminance (adaptation), where does the remaining adaptation come from?

Answer 11

The existence and properties of 2 classes of retinal photoreceptors, rods and cones

Question 12

Scotopic vision occurs under what kind of lighting conditions?

Answer 12

Dim

Question 13

VA for scotopic vision?

Answer 13

Poor VA (20/200 vision)

Question 14

What does scotopic vision have an absence of?

Answer 14

Color discrimination due to no cones being activated

Question 15

Scotopic vision is mediated by what?

Answer 15

Rods

Question 16

Photopic vision occurs under what kind of lighting conditions?

Answer 16

Bright light

Question 17

VA’s for photopic vision

Answer 17

Excellent VA’s (20/20)

Question 18

What does photopic vision have that scotopic vision does not?

Answer 18

Color discrimination (no rods are activated)

Question 19

What mediates photopic vision?

Answer 19

Cones

Question 20

What is meant by a duplex retina?

Answer 20

The existence of 2 classes of photoreceptors, each operating under different lighting conditions

Question 21

What contributes to vision under mesopic (twilight) conditions?

Answer 21

Both rods and cones

Question 22

What photopigment is contained within the discs of the rod’s outer segment?

Answer 22

Rhodopsin

Question 23

How many rods does one eye contain?

Answer 23

120 million rods

Question 24

How many disks does one rod contain?

Answer 24

1000

Question 25

How many rhodopsin molecules does one disk contain?

Answer 25

10,000

Question 26

The absorption of how many photons is sufficient to activate a rod?

Answer 26

1

Question 27

This is the first step in a sequence of events that ultimately leads to vision, where the absorption of light quanta by the photosensitive pigment in the outer segment causes the photoreceptor to become what?

Answer 27

Hyperpolarized

Question 28

Step one towards vision

Answer 28

Hyperpolarized