Vision Terms |
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| 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. |
| AQUEOUS HUMOR, AQUEOUS FLUID |
Clear, watery fluid that fills the front of the eye. |
ASTIGMATISM |
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. |
HYPEROPIA  |
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. |
MYOPIA  |
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. |
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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