Eye Physiology

Question 1

Which nerves control the pupillary reflex?

Answer 1

Cranial nerves II and III.

Autonomic nervous systems

Question 2

Stimulation of the parasympathetic nerves ________ the pupillary sphincter muscle, thereby ________ the pupillary ________.

Answer 2

Stimulation of the parasympathetic nerves excites the pupillary sphincter muscle, thereby decreasing the pupillary aperture (miosis)

Question 3

Sympathetic stimulation _______ the pupil.

Answer 3

Dilates (mydriasis)

Question 4

Direct Response

Answer 4

Pupil constricts when being illuminated.

Question 5

Consensual Response

Answer 5

Pupil constricts when contralateral pupil is illuminated.

Question 6

Accomodation

Answer 6

• Response to looking at something moving toward the eye.

- The ability to adjust the refractive power of the lens.

Question 7

Afferent pupillary defect

Answer 7

Decreased direct response caused by decreased visual function in one eye. The affected pupil will DILATE in response to light.

Question 8

Why do we have eyelashes?

Answer 8

Primarily to keep sweat out of the eye.

Question 9

3 things that can block pupillary reflex.

Answer 9

Alcoholism, Encephalitis, CNS Syphilis

Question 10

Which muscles does CN III (occulomotor) innervate?

Answer 10

Medial rectus: Turns medially
Superior rectus: Elevates eye and rolls upward.
Inferior rectus: Depresses eye and rolls down
Inferior oblique: Elevates eye and turns lateral

Question 11

Which muscle does CN IV (trochlear) innervate?

Answer 11

Superior oblique: Turns the eye down and out.

Question 12

Which muscle does CN VI (Abducens) innervate?

Answer 12

Lateral rectus: Moves eye laterally

Question 13

Conjugate Gaze

Answer 13

Refers to the use of both eyes to look steadily on one direction.

Question 14

Saccadic Eye Movements

Answer 14

Consists of small jumping movements that represent rapid shift in conjugate gaze orientation.

Question 15

Hippus

Answer 15

A reflex response of the pupil to light that is completely normal. Do not confuse with afferent pupillary defect.

Question 16

Nystagmus

Answer 16

The sequence of slow ocular rotation, a saccade, and slow rotation.

Question 17

T of F: The lens of the eye is extremely vascular.

Answer 17

False, the lens is Avascular

Question 18

The lens is ______ for distance vision.

Answer 18

Flattened. Sympathetic input relaxes the ciliary muscle, tightening the ciliary zonule and flattening the lens.

Question 19

The lens _______ for close vision.

Answer 19

Bulges. Parasympathetic input contracts ciliary muscle, loosening the ciliary zonule, allowing the lens to bulge.

Question 20

When light rays strike an interface that is perpendicular to the beam, rays ______ deviate from the course.

Answer 20

Do not.

Question 21

Which CN in in control of accommodation of the lens?

Answer 21

Parasympathetic division of CN III is in control.

Question 22

Suspension of the lens.

Answer 22

Occurs via 70 suspensory ligaments that attach radially around the lens. The hold constant tension of the lens, and if they were not there, the lens would assume a spherical shape.

Question 23

Meridional and circular fibers make up the?

Answer 23

Ciliary muscle

Question 24

What happens to the lens when the ciliary body contracts?

Answer 24

The ligaments relax, and the lens becomes more spherical, which is good for close vision.

Question 25

What controls the ciliary muscle?

Answer 25

Parasympathetic nerve signals from CN III.

Question 26

T of F. Sympathetic stimulation plays a large role in accommodation.

Answer 26

False, sympathetic fibers play almost no role in accommodation.

Question 27

Emmetropia

Answer 27

Normal vision.

Question 28

Presbyopia

Answer 28

``` Old Eyes. As a person grows older: -The lens grows larger and thicker -Lens becomes less elastic -Ability of lens to change shape decreases. -Less power for accommodation ```

Question 29

Hyperopia

Answer 29

Far-Sightedness (distant objects are seen clearly) | -Eyeball is too short so focal point is behind the retina.

Question 30

Myopia

Answer 30

Near-sightedness (Can see close objects) - Eyeball is too long so focal point is in front of retina. - The ciliary muscle can't relax enough to extend the focal point any further.

Question 31

Which type of lens will correct myopia?

Answer 31

Concave (bowtie)

Question 32

Which type of lens will correct hyperopia?

Answer 32

Convex (oval)

Question 33

Astigmatism

Answer 33

This is an abnormally shaped lens. Should be a golfball, but is an egg. No degree of accommodation can correct the error.

Question 34

Rods

Answer 34

Black and white vision

Question 35

Cones

Answer 35

Color vision. | There are blue, green and red cones that are specific for each of those colors.

Question 36

Disease of peripheral retina affects _____ cones.

Answer 36

Blue

Question 37

Diseases of the more central retina affect _____ and _____ cones because?

Answer 37

Red and Green because blue cones are not present in the central fovea.

Question 38

Males are more frequently affected with which color blindness?

Answer 38

Red, Green and Red/Green

Question 39

Moving Parallax

Answer 39

Relative distance of an object can be determined by the extent to which they move when the person moves their head back and forth. The farther it is, the less it moves across the retina.

Question 40

Stereopsis

Answer 40

Binocular vision. The distance of an object will determine the relative locations on the retina for each eye. -The closer, the further separated on the retina.

Question 41

Aqueous Humor

Answer 41

Intraocular fluid that is in front of the lens. | -freely flowing fluid.

Question 42

Vitreous Humor

Answer 42

Intraocular fluid that lies between the posterior surface of the lens and the retina. -Gelatinous mass, slow diffusion and very little fluid flow.

Question 43

Role of the intraocular fluid

Answer 43

Maintains sufficient pressure to keep eyeball distended.

Question 44

What forms the aqueous humor?

Answer 44

The ciliary body, at 2-3 microliters/minute.

Question 45

Average Intraocular Pressure

Answer 45

12-20mm Hg

Question 46

Glaucoma

Answer 46

One of the most common causes of blindness. -Intraocular pressure becomes pathologically high (as high as 60-70 mmHg) -Generally results from an increase in outflow resistance. Tx: Decrease production or increase absorption