Guyton Chapter 49

Front 1

Speed of light through air

Back 1

300,000 km/s

Front 2

If light travels 200,000 through glass, what is the reflective index of the glass?

Back 2

1.5 = 300k/200k

Front 3

bending of light rays at an angulated interface is known as

Back 3

refraction

Front 4

degree of refraction increases as a function of

Back 4

(1) the ratio of the two refractive indices of the two transparent media and (2) the degree of angulation between the interface and the entering wave front.

Front 5

What kind of lens focuses light rays?

Back 5

Convex Lens

Front 6

Outer rays bending more and more toward the center is called?

Back 6

Convergence

Front 7

if the lens has exactly the proper curvature, parallel light rays passing through each part of a convex lens will be bent exactly enough so that all the rays will pass through a single point, which is called?

Back 7

Focal point

Front 8

What kind of lens diverges light rays?

Back 8

Concave

Front 9

The more a lens bends light rays, the greater is its?

Back 9

refractive power

Front 10

Refractive power is measured in?

Back 10

diopters

Front 11

Refractive power in diopters of a convex lens is equal to?

Back 11

1 meter divided by its focal length.

Front 12

Lens system of the eye is composed of how many refractive interfaces?

Back 12

Four

Front 13

Refractive interfaces of the eye

Back 13

(1) the interface between air and the anterior surface of the cornea, (2) the interface between the posterior surface of the cornea and the aqueous humor, (3) the interface between the aqueous humor and the anterior surface of the lens of the eye, and (4) the interface between the posterior surface of the lens and the vitreous humor.

Front 14

Index of each medium in the eye

Back 14

The internal index of air is 1; the cornea, 1.38; the aqueous humor, 1.33; the crystalline lens (on average), 1.40; and the vitreous humor, 1.34.

Front 15

If all the refractive surfaces of the eye are algebraically added together and then considered to be one single lens, the eye has a total refractive lower of how many diopters?

Back 15

59 diopters

Front 16

The total refractive power of the internal lens of the eye?

Back 16

20 diopters

Front 17

Curvature of the internal lens can be increased by nervous signals from the brain. This is called?

Back 17

Accommodation

Front 18

Lateral attachment to the lens?

Back 18

70 suspensory ligaments

Front 19

Lateral attachment to the lens suspensory ligaments?

Back 19

Ciliary muscle

Front 20

Ciliary muscle is composed of what fibers?

Back 20

two separate sets of smooth muscle fibers—meridional fibers and circular fibers

Front 21

effect of ciliary muscle contraction on lens ligaments?

Back 21

Relaxes

Front 22

Accommodation is controlled by what autonomic system?

Back 22

Parasympathetic

Front 23

Accommodation is controlled by what nerve?

Back 23

Third cranial nerve

Front 24

Accommodation allows the objects to focus on close/distant objects?

Back 24

close objects

Front 25

As a person grows older, the lens remains almost totally nonaccommodating, a condition known as?

Back 25

presbyopia

Front 26

Clinical solution for presbyopia?

Back 26

bifocal glasses

Front 27

The major function of the iris?

Back 27

to increase the amount of light that enters the eye during darkness

Front 28

Diameter of the pupil (range)?

Back 28

as small as about 1.5 millimeters and as large as 8 millimeters in diameter

Front 29

If the retina can be displaced considerably with little change in focus, this indicates a high what?

Back 29

depth of focus

Front 30

What increases depth of focus?

Back 30

Decreased pupilary diameter

Front 31

Term for normal vision?

Back 31

Emmetropia

Front 32

Term for farsighted vision?

Back 32

Hyperopia

Front 33

Term for nearsighted vision?

Back 33

Myopia

Front 34

Causes of farsighted vision?

Back 34

eyeball that is too short or, occasionally, a lens system that is too weak

Front 35

Causes of nearsighted vision?

Back 35

too long an eyeball, or a lens system with too much refractive power

Front 36

For which condition (hyperopia or myopia) can the eye use accommodation to focus?

Back 36

Hyperopia

Front 37

Correction of Myopia and Hyperopia can be accomplished by use of which types of Lenses?

Back 37

Myopia - concave lens
Hyperopia - convex lens

Front 38

Define astigmatism.

Back 38

refractive error of the eye that causes the visual image in one plane to focus at a different distance from that of the plane at right angles

Front 39

Correction of astigmatism?

Back 39

Find a spherical lens by trial and error that corrects the focus in one of the two planes of the astigmatic lens. Then an additional cylindrical lens is used to correct the remaining error in the remaining plane.

Front 40

Odd-shaped, bulging cornea making wearing eye glasses difficult is a condition called?

Back 40

keratoconus

Front 41

Define cataract.

Back 41

A cataract is a cloudy or opaque area or areas in the lens caused by coagulating proteins.

Front 42

Cataract treatment?

Back 42

Surgical removal of the lens. Replaced by a powerful convex lens in front of the eye or usually, an artificial plastic lens is implanted in the eye

Front 43

average diameter of the cones in the fovea of the retina?

Back 43

1.5 micrometers

Front 44

size of the fovea?

Back 44

less than 0.5 millimeter (less than 500 micrometers) in diameter

Front 45

Three mechanisms for depth perception

Back 45

(1) known size of the image leading to a deduction of distance, (2) moving parallax , (3) stereopsis / binocular vision

Front 46

Fluid in front of the lens is called?

Back 46

Aqueous Humor

Front 47

Fluid behind the lens is called?

Back 47

Vitreous Humor

Front 48

Which fluid regulates the total volume and pressure of the intraocular fluid?

Back 48

Aqueous Humor

Front 49

Aqueous humor is formed in the eye at an average rate of?

Back 49

2 to 3 microliters each minute

Front 50

Aqueous humor is formed by?

Back 50

ciliary processes

Front 51

area of the ciliary processes?

Back 51

6 square centimeters in each eye

Front 52

Aqueous humor contains?

Back 52

chloride and bicarbonate ions, amino acids, ascorbic acid, and glucose.

Front 53

Outflow of aqueous humor is through what structure?

Back 53

canal of Schlemm

Front 54

intraocular pressure (average and range)

Back 54

15 mm Hg, with a range from 12 to 20 mm Hg.

Front 55

Intraocular pressure is measured by what instrument?

Back 55

Tonometer

Front 56

Define glaucoma

Back 56

intraocular pressure becomes pathologically high

Front 57

Long term effect of glaucoma?

Back 57

Blindness

Front 58

Most common cause of glaucoma?

Back 58

The abnormally high pressure results from increased resistance to fluid outflow through the trabecular spaces into the canal of Schlemm.