Colored circular membrane that is in front of the lens and controls the size of the opening at its center (pupil), thereby regulating the amount of light entering the eye.
Glossary of Eye and Vision Terms
Common terms to help you learn more about your eyes and vision
keratitis acanthamoeba
Acanthamoeba keratitis is sometimes referred to incorrectly as “keratitis acanthamoeba.” Find out more about acanthamoeba keratitis
Laser
Surgical tool using an intense beam of light energy to close rips, make holes, destroy new vessels (photocoagulation), or to open channels as in the treatment of glaucoma.
Legal Blindness
Visual acuity that does not exceed 20/200 in the better eye with correcting lens; field of vision no greater than 20 degrees in its widest angle (Visual acuity of 20/200
Lens
The transparent disc in the middle of the eye behind the pupil that brings rays of light into focus on the retina.
Low-Vision Aids
Powerful optical devices useful to persons with vision impairments that are not successfully corrected by the usual prescription lenses.
Macula
The region of the retina that helps provide best central vision. The fovea is at the center of the macula.
Matricular degeneration
This is a common misspelling of macular degeneration. Find out more about age-related macular degeneration
Myopia
Myopia (my-OH-pea-uh), or nearsightedness, is a vision condition in which distant objects appear blurred – such as roadway signs, the board at school, faces, or the television set across the
Near Vision
The ability to perceive objects distinctly at normal reading distance (usually about 14 inches from the eye).
Nearsightedness
Myopia (my-OH-pea-uh), or nearsightedness, is a vision condition in which distant objects appear blurred – such as roadway signs, the board at school, faces, or the television set across the
Night Blindness
Condition in which sight is good by day but deficient at night and in any faint light.
