Glossary of Eye and Vision Terms

Common terms to help you learn more about your eyes and vision


In testing the visual field, this is the blind area corresponding to the optic disk where the optic nerve fibers exit the eye and where there are no light-sensitive cells.

Central Visual Field

The area of objects in space seen without moving the head or eyes; corresponds to an area within 30º of the fixation point (fovea).


The middle layer of the eye containing blood vessels that furnish nourishment to the other parts of the eye, especially the retina.

Ciliary Body

A ring of tissue between the iris and the choroid consisting of muscles and blood vessels that changes the shape of the lens and manufactures aqueous humor.


Cone-shaped light-sensitive cells in the retina particularly in the macula area; cone function predominates in daylight with a small pupil allowing one to make out details and shapes, especially colors.

congenital glaucoma

Congenital/childhood/pediatric glaucoma is glaucoma diagnosed early in a child’s life, as infants or young children. It causes increased intraocular pressure that can damage the optic nerve in the back of the eye. Find out more about glaucoma


Delicate tissue that lines the inside of the eyelids and covers the front part of the eye except the cornea.


The clear curved structure that comprises the front of the eye, a refractive surface through which light enters.