Eye Health Glossary
Pinkeye: See conjunctivitis.
Presbyopia: The loss of the eye's ability to change its focus to see objects that are near. Presbyopia is not a disease, but a part of the natural aging process of the eye that affects everybody at some point in life. It generally starts to appear around age 40 to 45.
Pupil: The round, dark, central opening of the eye through which light enters.
Refraction: The ability of the eye to bend light so that an image focuses directly on the retina.
Refractive error: A condition in which light bends incorrectly, causing an image to be out of focus. The most common refractive errors are astigmatism, farsightedness, and nearsightedness. When you receive a prescription for glasses or contact lenses from your eye doctor, it's to correct a refractive error.
Retina: The thin layer of nerves that lines the back of the eye. The retina senses light and transmits light impulses to the optic nerve and then the brain.
Retinitis pigmentosa: Any of a number of inherited disorders in which there is a progressive loss of vision. In general, patients with this disorder first experience a loss of night vision, which is then followed by tunnel vision and eventually a loss of central vision.
Retinoblastoma: A malignant tumor that forms on the retina. Retinoblastoma most often affects children under the age of 5. It can occur in one or both eyes.
Sclera: The outer coat of the eyeball that forms the whites of a person's eyes.
Strabismus: A condition in which the eyes are misaligned and unable to point in the same direction at the same time. Crossed eyes is an example of strabismus.
Tunnel vision: A condition in which a person lacks any peripheral vision. Tunnel vision can be caused by any number of conditions including retinitis pigmentosa, untreated glaucoma, and stroke.
Visual acuity: How well a person sees.
Visual field: The entire range in which a person can see, including peripheral vision.
Vitrectomy: A procedure in which the vitreous humor is removed from the eyeball and replaced with a clear gel or liquid. Vitrectomies are done when scarring or blood in the vitreous is causing blockage of vision.
Vitreous humor: The clear gel-like substance found inside the center of the eyeball.