Glossary of Terms

Ophthalmologist: An ophthalmologist is either a medical doctor (M.D.) or an osteopathic physician (D.O.) who is qualified and especially trained to diagnose and treat all eye and visual system problems, both medically and surgically, as well as diagnose general diseases of the body. Training involves four years of undergraduate college, four years of medical school and four years of residency training specializing in medical and surgical care of the eyes.

Optometrist: An eye care professional who is a graduate of optometry school who provides non-surgical visual care. Specifically educated and trained to examine the eyes and to determine visual acuity as well as other vision problems and ocular abnormalities. An optometrist prescribes glasses and contact lenses to improve visual acuity.

Optician: An expert who designs, verifies and dispenses lenses, frames and other fabricated optical devices upon the prescription of an ophthalmologist or an optometrist.

Anterior Chamber: The space between the cornea and the iris and lens.

Aqueous Humor: Transparent fluid that fills the anterior chamber and maintains eye pressure. It is also essential in providing nutrition to the cornea and lens.

Ciliary Body: Part of the eye that produces aqueous humor and maintains eye pressure. It also is attached to the lens and aids in accommodation (the ability to focus between distant objects and near objects).

Conjunctiva: The mucous membrane lining the inner surface of the eyelids and covering the front part of the sclera (white part of the eye), responsible for keeping the eye moist.

Cornea: The transparent tissue that forms the front part of the eyeball, covering the iris and pupil. The cornea is the first part of the eye that bends (or refracts) light and provides most of the focusing power.

Iris: The colored part of the eye. It is an elastic, pigmented, muscular tissue in front of the crystalline lens that regulates the amount of light that enters the eye by adjusting the size of the pupil in the center.

Lens: A double convex, clear structure of the eye that is located behind the iris and in front of the vitreous humor. It serves to refract light rays entering the eye to help form a focused image on the retina.

Pupil: The black circular opening in the center of the iris through which light passes into the crystalline lens. It changes size in response to how much light is being received by the eye; it is larger in dim lighting conditions and smaller in brighter lighting conditions.

Optic Nerve: A bundle of nerve fibers that connect the retina to the brain (the “cable” from the eye to the brain). The optic nerve carries signals of light from the retina to a part of the brain known as the visual cortex. Here, these light signals are assembled into images known as vision.

Retina: An extension of brain tissue, this fine sensory tissue lines the inside wall of the eye and is composed of light sensitive cells known as rods and cones. The retina acts like the film to a camera; it captures images and transforms these images into electrical signals that are transmitted to the brain by the optic nerve.

Sclera: White part of the eye. Tough covering that (with the cornea) forms the external, protective coat of the eye.

Vitreous Humor: The jelly-like, transparent substance that fills the large cavity in the back of the eye, between the lens and the retina. The natural degeneration of this jelly is what causes the “floater” that one often sees.