Eye Test Review

What percentage of all sensory receptors are located in the eye?

70% photoreceptors

How long is the eyeball in diameter?

2.5 cm

What protects and encloses the eyeball?

cushion of fat

Eyebrows

shade and protect

Eyelids

“palpebrae;” protect, cause reflex blinking

Eyelashes

many nerve endings, protect

Conjunvtiva

mucous membrane lining inner surface of eyelid

Conjunctivitis

inflammation, red and irritated eyes, “pink eye” caused by a virus

Lacrimal apparatus

produces tears

Sclera

white, protects and shapes

Pupil

black “hole,” lets light in

Cornea

clear window over iris and pupil, can be transplanted

Iris

colored ring made of smooth muscle fibers which regulate size of pupil

Lens

behind iris, biconvex, transparent, changes shape to allow focusing on retina

Retina

layer lining inside of eyeball, contains photoreceptors

What are the 2 types of photoreceptors?

rods and cones

Rods

for dim light vision and peripheral vision

Cones

for color vision

Macula

(fovea centralis) pigmented area near center of retina for detailed color vision

Ciliary Body

thick ring of tissue encircling the lens

Optic Nerve

nerve that exits back of eye, sends sight messages to brain

Optic Disc

“blindspot;” located where optic nerve exits the eye, contains no photoreceptors

What are the 2 humors (fluids) in the eyeball?

vitreous and aqueous

Vitreous Humor

posterior cavity behind iris, supports, transmits light, thick and gel-like

Aqueous Humor

anterior between iris and lens, supplies nutrients to and oxygen to lens and cornea, supports, watery substance

Myopia

nearsightedness, can see near, object is focused in front of the retina

Causes of myopia

long eyeball, cornea is too curved, lens is too thick

Hyperopia

farsightedness, can see far, object is focused behind the retina

Causes of hyperopia

flat cornea, short eyeball

Astigmatism

abnormal curvature in the lens, fuzzy vision because there are 2 or more focal points and none land on the retina like they should

Cataracts

clouding of the lens due to decreased blood flow to the eye, replace lens with artificial one

Glaucoma

series of eye diseases that damage the optic nerve; cannot be cured

Causes of glaucoma

build up of fluid (pressure) in anterior chamber

Macular Degeneration

blurred or no vision in the center of the visual field; caused by damage to macula of retina; age related

Laser Corrective Surgery (LASIK)

laser used to reshape cornea to correct vision