Anatomy And Physiology Of The Eye

Front 1

choroid (KOR-oyd)

Back 1

Vascular (major blood vessel) layer of the eye lying between the retina and the sclera. Provides nourishment to outer layers of the retina.

Front 2

cone.

Back 2

Light-sensitive retinal receptor cell that provides sharp visual acuity and color discrimination.

Front 3

conjunctiva

Back 3

Transparent muccous membrane covering the outer surface of the eyeball except the cornea, and lining the inner surfaces of the eyelids.

Front 4

conjunctivitis (kun-junk-tih-VI-tis), "pink eye."

Back 4

Inflammation of the conjunctiva. Characterized by discharge, grittiness, redness and swelling. Usually viral in origin, but may be bacterial or allergic; may be contageous.

Front 5

cornea (KOR-nee-uh).

Back 5

Transparent front part of the eye that covers the iris, pupil, and anterior chamber and provides most of an eye's optical power.

Front 6

crystalline lens.

Back 6

The eye's natural lens. Transparent, biconvex intraocular tissue that helps bring rays of light to a focus on the retina.

Front 7

cataract.

Back 7

Opacity or cloudiness of the crystalline lens, which may prevent a clear image from forming on the retina. Surgical removal of the lens may be necessary if visual loss becomes significant, with lost optical power replaced with an intraocular lens, contact lens, or aphakic spectacles. May be congenital or caused by trauma, disease, or age.

Front 8

accommodation (uh-kah-muh-DAY-shun).

Back 8

accommodation (uh-kah-muh-DAY-shun). Increase in optical power by the eye in order to maintain a clear image (focus) as objects are moved closer. Occurs through a process of ciliary muscle contraction and zonular relaxation that causes the elastic-like lens to "round up" and increase its optical power. Natural loss of accommodation with increasing age is called presbyopia.

Front 9

age-related macular degeneration (AMD, ARMD) (MAK-yu-lur).

Back 9

Group of conditions that include deterioration of the macula, resulting in loss of sharp central vision. Two general types: "dry," which is more common, and "wet," in which abnormal new blood vessels grow under the retina and leak fluid and blood (neovascularization), further disturbing macular function. Most common cause of decreased vision after age 60.

Front 10

amblyopia (am-blee-OH-pee-uh), "lazy eye."

Back 10

Decreased vision in one or both eyes without detectable anatomic damage in the eye or visual pathways. Usually uncorrectable by eyeglasses or contact lenses.

Front 11

angle, anterior chamber angle.

Back 11

Junction of the front surface of the iris and back surface of the cornea, where aqueous fluid filters out of the eye.

Front 12

anterior chamber

Back 12

Fluid-filled space inside the eye between the iris and the innermost corneal surface (endothelium).

Front 13

aqueous (AY-kwee-us), aqueous humor.

Back 13

Clear, watery fluid that fills the space between the back surface of the cornea and the front surface of the vitreous, bathing the lens. Produced by the ciliary processes. Nourishes the cornea, iris, and lens and maintains intraocular pressure.

Front 14

binocular vision.

Back 14

Blending of the separate images seen by each eye into one composite image.

Front 15

blepharitis (blef-uh-RI-tus).

Back 15

Inflammation of the eyelids, usually with redness, swelling, and itching.

Front 16

blind spot

Back 16

Sightless area within the visual field of a normal eye. Caused by absence of light sensitive photoreceptors where the optic nerve enters the eye.

Front 17

chalazion (kuh-LAY-zee-un).

Back 17

Inflammed lump in a meibomian gland (in the eyelid). Inflammation usually subsides, but may need surgical removal. Sometimes called an internal hordeolum.

Front 18

dilated pupil.

Back 18

Enlarged pupil, resulting from contraction of the dilator muscle or relaxation of the iris sphincter. Occurs normally in dim illumination, or may be produced by certain drugs (mydriatics, cycloplegics) or result from blunt trauma.

Front 19

diopter (D) (di-AHP-tur).

Back 19

Unit to designate the refractive power of a lens.

Front 20

diplopia, double vision.

Back 20

Perception of two images from one object; images may be horizontal, vertical or diagonal.

Front 21

dry eye syndrome.

Back 21

Corneal and conjunctival dryness due to deficient tear production, predominantly in menopausal and post-menopausal women. Can cause foreign body sensation, burning eyes, filamentary keratitis, and erosion of conjunctival and corneal epithelium.

Front 22

ectropion (ek-TROH-pee-un).

Back 22

Outward turning of the upper or lower eyelid so that the lid margin does not rest against the eyeball, but falls or is pulled away. Can create corneal exposure with excessive drying, tearing, and irritation. Usually from aging.

Front 23

entropion (en-TROH-pee-un).

Back 23

Inward turning of upper or lower eyelid so that the lid margin rests against and rubs the eyeball.

Front 24

esotropia (ee-soh-TROH-pee-uh), cross-eyes.

Back 24

Eye misalignment in which one eye deviates inward (toward nose) while the other fixates normally.

Front 25

exotropia (eks-oh-TROH-pee-uh), wall-eyes.

Back 25

Eye misalignment in which one eye deviates outward (away from nose) while the other fixates normally

Front 26

extraocular muscles (eks-truh-AHK-yu-lur).

Back 26

Six muscles that move the eyeball (lateral rectus, medial rectus, superior oblique, inferior oblique, superior rectus, inferior rectus).

Front 27

eyelids.

Back 27

Structures covering the front of the eye, which protect it, limit the amount of light entering the pupil, and distribute tear film over the exposed corneal surface.

Front 28

floaters.

Back 28

Particles that float in the vitreous and cast shadows on the retina; seen as spots, cobwebs, spiders, etc. Occurs normally with aging or with vitreous detachment, retinal tears, or inflammation.

Front 29

fovea (FOH-vee-uh).

Back 29

Central pit in the macula that produces sharpest vision. Contains a high concentration of cones and no retinal blood vessels

Front 30

fundus.

Back 30

Interior posterior surface of the eyeball; includes retina, optic disc, macula, posterior pole. Can be seen with an ophthalmoscope.

Front 31

glaucoma (glaw-KOH-muh).

Back 31

Group of diseases characterized by increased intraocular pressure resulting in damage to the optic nerve and retinal nerve fibers. A common cause of preventable vision loss. May be treated by prescription drugs or surgery.

Front 32

hyphema (hi-FEE-muh).

Back 32

Blood in the anterior chamber, such as following blunt trauma to the eyeball.

Front 33

intraocular pressure

Back 33

Fluid pressure inside the eye. 2. The assessment of pressure inside the eye with a tonometer. Also called tension.

Front 34

IOL (intraocular lens).

Back 34

Plastic lens that may be surgically implanted to replace the eye's natural lens.

Front 35

iris.

Back 35

Pigmented tissue lying behind the cornea that gives color to the eye (e.g., blue eyes) and controls amount of light entering the eye by varying the size of the pupillary opening.

Front 36

keratometry (kehr-uh-TAH-mih-tree).

Back 36

Obtaining corneal curvature measurements with a keratometer.

Front 37

lacrimal gland

Back 37

Almond-shaped structure that produces tears. Located at the upper outer region of the orbit, above the eyeball.

Front 38

lens, crystalline lens.

Back 38

The eye's natural lens. Transparent, biconvex intraocular tissue that helps bring rays of light to a focus on the retina.

Front 39

macula.

Back 39

Small central area of the retina surrounding the fovea; area of acute central vision.

Front 40

myopia (mi-OH-pee-uh), nearsightedness

Back 40

Focusing defect in which the eye is overpowered. Light rays coming from a distant object are brought to focus in front of the retina. Requires a minus lens correction to "weaken" the eye optically and permit clear distance vision.

Front 41

optic disc, optic nerve head

Back 41

Ocular end of the optic nerve. Denotes the exit of retinal nerve fibers from the eye and entrance of blood vessels to the eye.

Front 42

optic nerve

Back 42

Largest sensory nerve of the eye; carries impulses for sight from the retina to the brain.

Front 43

peripheral vision

Back 43

Side vision; vision elicited by stimuli falling on retinal areas distant from the macula.

Front 44

presbyopia (prez-bee-OH-pee-uh).

Back 44

Refractive condition in which there is a diminished power of accommodation arising from loss of elasticity of the crystalline lens, as occurs with aging. Usually becomes significant after age 45.

Front 45

ptosis (TOH-sis).

Back 45

Drooping of upper eyelid. May be congenital or caused by paralysis or weakness of the 3rd cranial nerve or sympathetic nerves, or by excessive weight of the upper lids.

Front 46

pupil.

Back 46

Variable-sized black circular opening in the center of the iris that regulates the amount of light that enters the eye.

Front 47

retina (RET-ih-nuh

Back 47

Light sensitive nerve tissue in the eye that converts images from the eye's optical system into electrical impulses that are sent along the optic nerve to the brain. Forms a thin membranous lining of the rear two-thirds of the globe

Front 48

rod

Back 48

Light-sensitive, specialized retinal receptor cell that works at low light levels (night vision). A normal retina contains 150 million rods.

Front 49

Schlemm's canal (shlemz).

Back 49

Circular channel deep in corneoscleral junction (limbus) that carries aqueous fluid from the anterior chamber of the eye to the bloodstream

Front 50

sclera (SKLEH-ruh).

Back 50

Opaque, fibrous, protective outer layer of the eye ("white of the eye") that is directly continuous with the cornea in front and with the sheath covering optic nerve behind.

Front 51

strabismus (struh-BIZ-mus).

Back 51

Eye misalignment caused by extraocular muscle imbalance: one fovea is not directed at the same object as the other

Front 52

sty, stye

Back 52

Acute pustular infection of the oil glands of Zeis, located in an eyelash follicle at the eyelid margin.

Front 53

trabecular meshwork (truh-BEK-yu-lur).

Back 53

Mesh-like structure inside the eye at the iris-scleral junction of the anterior chamber angle. Filters aqueous fluid and controls its flow into the canal of Schlemm, prior to its leaving the anterior chamber

Front 54

uvea, uveal tract (YU-vee-uh).

Back 54

Pigmented layers of the eye (iris, ciliary body, choroid) that contain most of the intraocular blood vessels

Front 55

vitreous (VlT-ree-us), vitreous humor

Back 55

Transparent, colorless gelatinous mass that fills the rear two-thirds of the eyeball, between the lens and the retina

Front 56

zonules (ZAHN-yoolz).

Back 56

Radially arranged fibers that suspend the lens from the ciliary body and hold it in position.

Front 57

wall-eyes

Back 57

Eye misalignment in which one eye deviates outward (away from nose) while the other fixates normally

Front 58

corneal abrasion

Back 58

A tearing, scrape or puncture of the cornea, sometimes accompanied by a loss of epithelium, the outer tissue layer of the cornea. Although a corneal abrasion can be very painful, the corneal layer of the eye heals more quickly than most other tissues in the human body

Front 59

corneal ulcers

Back 59

Wound on the surface of the eye similar to a scrape or cut on the skin. The cornea is covered by a layer of tissue called the epithelium which, when damaged can result in infection if left untreated. Corneal ulcers have many causes including injury, abnormal eyelashes, absence of tear production and infections. Persistent irritation or redness is reason to see an eye doctor.

Front 60

crossed eyes

Back 60

Also known as strabismus, this condition is a visual defect in which the eyes are misaligned and point in different directions. Strabismus usually occurs in childhood, but it can occur later in life. Children with crossed eyes usually adapt when the brain learns to ignore the image of the misaligned eye, although they lose depth perception. Adults who develop the problem often have double vision because the brain is already trained to see two images.

Front 61

absorption spectrum

Back 61

The relationship between wavelengths of light striking a pigment and how strongly the light is absorbed.

Front 62

amacrine cell

Back 62

A type of neuron seen in the retina.

Front 63

anterior

Back 63

Front or forward area of an object.

Front 64

anterior segment

Back 64

Front third of eyeball, including the cornea, anterior chamber, iris and ciliary body.

Front 65

Bell’s Palsy and the eye

Back 65

Paralysis of muscles controlled by the facial cranial nerve. Eyelid on affected side does not close properly, so corneal drying may become a problem

Front 66

diplopia

Back 66

The condition whereby a single object appears as two objects. Occurs because the eye muscles do not act equally. Also called double vision

Front 67

drooping eyelids

Back 67

Condition (usually hereditary) in which the upper eyelid(s) sag. May be congenital or caused by a later problem associated with a nonfunctioning levator muscle

Front 68

ectropion

Back 68

An abnormal turning out of an eyelid.

Front 69

emmetropia

Back 69

Refractive condition in which no refractive error is present. In other words, perfect 20/20 vision. Distant images are focused sharply on the retina without the need for corrective lenses

Front 70

enucleation

Back 70

Surgical removal of a diseased or damaged eyeball, leaving eye muscles and remaining orbital contents intact.

Front 71

epiphora

Back 71

Overflow of tears down the cheek caused by defective tear drainage system or by excessive flow of tears.

Front 72

eye

Back 72

A sensitive, sphere-shaped sense organ that acts as a “window,” allowing light waves to enter the body and be sent to the brain where they are converted into images. The eye works much like a camera with two lenses. Light entering the eye passes first through the cornea where it is focused through the pupil on the inner lens. The inner lens “fine tunes” and focuses the light on the retina at the back of the eye, which acts much like the film in a camera. The retina then transmits the light pattern to the brain through the optic nerve where an image is created.

Front 73

eyelid

Back 73

Structures covering front of the eye that protect the eye, limit the amount of light entering the pupil, and distribute tear film over the exposed corneal surface.

Front 74

inferior

Back 74

In eyecare terminology, referring to the lower half of the eye

Front 75

iris

Back 75

Ring of pigmented tissue lying behind the cornea that gives color to the eye and controls the amount of light entering the eye by varying the size of the pupil

Front 76

iritis

Back 76

Inflammation of the iris causing pain, tearing, blurred vision, small pupil, and a red congested eye.

Front 77

lateral geniculate nucleus

Back 77

Structure in the thalmus, which is a major recipient of axons from the retina

Front 78

luminance

Back 78

The amount of light coming off a surface.

Front 79

lysozyme

Back 79

A basic protein that is present in egg white, saliva, and tears.

Front 80

medial

Back 80

Medical term used to indicate “nasal or towards the nose

Front 81

meibomian gland

Back 81

Little glands in the eyelids that make a fatty lubricant which they discharge through tiny openings in the edges of the lids. The meibomian glands can become inflamed, a condition termed meibomianitis or meibomitis. Chronic inflammation of the meibomian glands leads to a cyst, also called chalazion, which is a pimple in the margin of the eyelid. The meibomian glands are also known as the palpebral glands, tarsal glands, or tarsoconjunctival glands.

Front 82

melanin

Back 82

Black pigment in the pigment epithelium cells that absorbs light not captured by the retina, thereby preventing the light from being reflected off the back of the eye.

Front 83

mesopic

Back 83

Intensities of light under which both cones and rods operate.

Front 84

mucoprotein
mucoid

Back 84

Any of a group of various complex conjugated proteins that occur in body fluids and tissues.

Front 85

mydriasis

Back 85

Increase in pupil size (dilation) occurring normally in the dark. May occur artificially through the use of drugs.

Front 86

nasal lacrimal system

Back 86

That portion of the lacrimal (tear producing) system that includes ducts which drain tears from the eye into the nose.

Front 87

nasal lacrimal duct

Back 87

Tear drainage channel that extends from lacrimal sac to opening in mucous membrane of nose.

Front 88

occlusion

Back 88

The transient approximation of the edges of a natural opening, i.e., occlusion of the eyelids

Front 89

ocular

Back 89

Of, pertaining to, or affecting the eye

Front 90

ocular hypertension

Back 90

Condition in which the intraocular pressure of the eye is elevated above normal without any obvious optic nerve damage or visual field defects. Over time, ocular hypertension may develop into glaucoma

Front 91

ocular motility

Back 91

The movement of the eye.

Front 92

opsin

Back 92

Protein portion of the visual pigment of rod cells.

Front 93

optic nerve pathways

Back 93

The left and right branches of the optic nerves join behind the eyes, just in front of the pituitary gland, to form a cross-shaped structure called the optic chiasma. Within the optic chiasma, some of the nerve fibers cross. The fibers from the nasal (inside) half of each retina cross over, but those from the temporal (outside) half do not. Specifically, the fibers from the nasal half of the left eye and the temporal half of the right eye form the right optic tract; and the fibers from the nasal half of the right eye and the temporal half of the left form the left optic tract. The nerve fibers then continue along in the optic tracts. Just before they reach the thalamus of the brain, a few of the nerve fibers leave to enter nerve nuclei that function in visual reflexes. Most of the nerve fibers enter the thalamus, forming a junction (synapse) in the back of the thalamus. From there the visual impulses enter nerve pathways called the optic radiations, which lead to the visual (sight) cortex of the occipital (back) lobes of the brain

Front 94

orbit

Back 94

Pyramid-shaped cavity in the skull containing the eyeball, its muscles, blood supply, nerve supply and fat.

Front 95

photoreceptor

Back 95

Cells specialized for receiving light.

Front 96

pole

Back 96

Posterior pole refers to back curvature of eyeballs, usually to the retina between optic nerve and macular area. Anterior pole refers to center of front surface of cornea.

Front 97

posterior

Back 97

Back area of an object.

Front 98

posterior chamber

Back 98

In referring to the eye, that space between the back which is filled with aqueous fluid between the iris and front face of the vitreous

Front 99

sclera

Back 99

Tough outermost layer of the eye that is visible as the white of the eye.

Front 100

scotoma

Back 100

Nonseeing area, or blind spot, within visual field, resulting from damage to visual pathways or to the retina. Blind spots exist normally in all eyes and mark the site of the optic nerve

Front 101

segment

Back 101

Term used in designating different areas of eye, as in “posterior segment” or “anterior segment

Front 102

spots

Back 102

Particles that float in the vitreous, which is jelly-like substance that fills the center cavity of the eye, and cast shadows on the retina. Some spots are formed before birth while others occur normally with aging. The sudden appearance of many spots can be an indication of a serious eye disorder and should be checked by your eye doctor

Front 103

superior

Back 103

In eye care terminology, referring to the upper half of the eye.

Front 104

superior colliculus

Back 104

Part of the brain that constitutes a primitive center for vision. Also called optic lobe, optic tectum.

Front 105

sympathetic ophthalmia

Back 105

Inflammation of one eye following inflammation in the other eye.

Front 106

tapetum

Back 106

Silvery lining behind the retina in some animals active in dim light. Reflects light back through the eye and allows the photoreceptors a second chance to absorb photons.

Front 107

tarsal glands
tarsoconjunctival glands

Back 107

Little glands in the eyelids that make a fatty lubricant which they discharge through tiny openings in the edges of the lids. The meibomian glands can become inflamed, a condition termed meibomianitis or meibomitis. Chronic inflammation of the meibomian glands lead to a cyst, also called chalazion, which is a pimple in the margin of the eyelid. The meibomian glands are also known as the meibomian glands, or palpebral glands.

Front 108

temple

Back 108

Side pieces of an eyeglass frame that hook over or behind the ear to hold the glasses firmly in place

Front 109

temporal

Back 109

Eye care terminology referring to the direction leading toward the ear or temple, away from the nose.

Front 110

trachoma

Back 110

Severe, chronic, contagious conjunctival eyelid and corneal infection caused by a virus. Leads to corneal blood vessel formation, corneal clouding, conjunctival and eyelid scarring and dry eyes. Leading cause of blindness in the world

Front 111

uveitis

Back 111

A disease, often misdiagnosed, that causes inflammation of the structures of the uveal tract: iris, ciliary body or choroid. Inflammation may occur suddenly, be chronic, or be recurrent. Symptoms include eye pain, sensitivity to light, blurred vision, tearing and redness. Uveitis is often related to a systemic condition such as rheumatoid arthritis, multiple sclerosis, sarcoidosis and ankylosing spondylitis. Usual treatment is administration of eye drops to relieve symptoms and reduce inflammation.