Chapter 50: The Eye: I. Optics of Vision

Question 1

Equipment used in Measuring Intraocular Pressure

Answer 1

Tonometer

Question 2

The average normal intraocular pressure

Answer 2

15 mmHg or 12-20mmHg

Question 3

The average amount of fluid leaving the eye via the canal of Schlemm

Answer 3

2.5 μl/min and equals the inflow of fluid from the ciliary body

Question 4

These are cells that have an extremely high capacity for engulfing debris and digesting it into small molecular substances that can then be absorbed in the canal of Schlemm

Answer 4

reticuloendothelial cells

Question 5

This is a disease of the eye in which the intraocular pressure becomes pathologically high, sometimes rising acutely to 60 to 70 mm Hg

Answer 5

glaucoma

Question 6

Which cell types is most likely to play a central role in lateral inhibition to enhance visual contrast?

Answer 6

Horizontal cells

Question 7

This pertains to a displacement in the apparent position of an object viewed along two different lines of sight, used by the eyes in determining distance

Answer 7

moving parallax

If a person looks off into the distance with the eyes completely still, he or she perceives no moving parallax, but when the person moves the head to one side or the other, the images of nearby objects move rapidly across the retinas, whereas the images of distant objects remain almost completely stationary.

Question 8

Three main means that a person normally perceives distance (depth perception):

Answer 8

1. size of the image in the retina
2. moving parallax
3. stereopsis

Question 9

This is a type of parallax that is always present when both eyes are
being used. It is almost entirely this binocular parallax (or stereopsis)
that gives a person with two eyes far greater ability to
judge relative distances when objects are nearby than a person
who has only one eye. However, stereopsis is virtually useless
for depth perception at distances beyond 50 to 200 feet.

Question 9

This is a type of parallax that is always present when both eyes are being used. This is almost entirely what gives a person with two eyes far greater ability to judge relative distances when objects are nearby than a person who has only one eye. However, this is virtually useless for depth perception at distances beyond 50 to 200 feet.

Answer 9

binocular parallax (or stereopsis)

Question 10

What receptors are blocked by atropine?

Answer 10

muscarinic receptors

Question 11

When the eyes fixate on a near object, the signals that cause accommodation of the lens, and those that cause convergence of the two eyes, cause a mild degree of pupillary constriction at the same time. This phenomenon is called the:

Answer 11

pupillary reaction to accommodation

Question 12

What is the total refractive power of the reduced eye when the lens is accommodated in distal vision?

Answer 12

59 diopters

Question 13

Refractive index of the cornea

Answer 13

1.38

Question 14

Refractive index of the aqueous humor

Answer 14

1.33

Question 15

Refractive index of the lens

Answer 15

1.40 on average

Question 16

Refractive index of the vitreous humor

Answer 16

1.34

Question 17

The total refractive power of the internal lens of the eye, as it normally lies in the eye surrounded by fluid on each side, is only:

Answer 17

20 diopters (1/3 of 59)

cornea = 2/3 = 39