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Vision Terms

EyeSearch is a Guide to Vision and the Eye, including information on glasses, contact lenses, eye diseases, eye surgery, laser surgery, including laser vision correction, and directories of eye specialists nationwide, including ophthalmologists, optometrists, opticians and low vision services

Refractive Disorders

Eye Anatomy

ACCOMMODATION The ability of the eye to change its focus from distant to near objects; this occurs when the lens inside the eye changes its shape.
Clear, watery fluid that fills the front of the eye.
A condition in which the surface of the cornea is not spherical; creates blurriness or "distortion" at all distances because light is not focused symmetrically on the retina.
BLIND SPOT (1) A small area of the retina where the optic nerve enters the eye; occurs normally in all eyes.
(2) Any gap in the visual field corresponding to a area of the retina where no visual cells are present; associated with eye disease.
CENTRAL VISION The area of vision used for fine detail straight ahead; perfect vision measures 20/20.
CILIARY MUSCLES The muscles that enable the lens to change shape for focusing.
CONES One of two types of light receptor cells in the retina. Cones see fine detail and color best.
CONJUNCTIVA The mucous membrane lining the inner surfaces of the eyelids and the outer surface of the white of the eye.
CORNEA The clear, strong surface layer of the eye covering the iris and pupil.
DILATION Enlarging the pupil, usually with eyedrops
FUNDUS The interior of the eye, seen best after dilation.
Farsightedness; (usually seeing at distance better than at near)
INTRAOCULAR PRESSURE (IOP) The fluid pressure inside the eye.
IRIS The colored part of the eye surrounding the pupil.
LENS The eye's natural internal focusing structure.
LEGAL BLINDNESS In the U.S.,  visual acuity of 20/200 or worse in the better eye with corrective lenses.
MACULA The central area of the retina where most of the cones are located - provides fine detail vision.
Nearsightedness; (usually seeing at near better than at distance.)
OPTIC DISC The area where the optic nerve connects to the retina.
OPTIC NERVE The nerve that sends messages from the eye to the brain.
PERIPHERAL VISION Side vision; seeing objects or movement to the side of the direction of gaze.
PRESBYOPIA The gradual loss of the eye's ability to change focus from distance to near; occurs in almost everyone sometime after age 40.
PUPIL The black circle in the center of the iris that opens and closes to allow light into the eye.
Normal Retina
The layer of light receptor cells at the back of the eye which forms an image that is sent to the brain.
RODS, ROD CELLS One of two types of light receptor cells in the retina; rods see in dim light and provide side vision.
SCLERA The tough, white, outer layer of the eyeball; with the cornea, it protects the entire eyeball.
TRABECULAR MESHWORK The area where fluid drains out of the eye.
VISUAL ACUITY The ability to see fine detail - "perfect" visual acuity is 20/20.
VISUAL FIELD The entire area that the eye can see from side to side (includes peripheral vision).
VITREOUS The thick gelatinous material that fills the back of the eye in front of the retina.

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