Glossary of Terms

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Albinism: A lack of pigment in the eyes, skin, or hair. While there are different types of albinism, many people with albinism are visually impaired and, in some cases, are legally blind. Individuals with albinism are sensitive to bright light and glare and often have other vision problems. For example, Albinism is often accompanied by nystagmus or strabismus.

Assistive Technology (AT): Technology that enables people who are blind or visually impaired to more easily access computers and the Internet. Columbia Lighthouse for the Blind’s “AT Center” in Silver Spring, MD, provides access to voice synthesizers, navigators, scanners, text enlargement software, and Braille output devices.

Braille: A system of writing or printing, devised by Louis Braille in 1824, for use by people who are blind or visually impaired. The system uses raised dots that are read by touch.

Cataracts: A cloudy area in the lens of the eye that blocks light from reaching the retina and may cause vision problems. It is common in older adults and associated with aging. Cataracts can cause blindness, although this is rare.

Diabetes: A disease in which the body does not produce or properly use insulin. It is the leading cause of blindness. (See diabetic retinopathy.)

Diabetic Retinopathy: The result of high blood sugar that, if left untreated, can lead to blindness. Too much blood glucose can destroy the blood vessels in the back of the eye, preventing the retina from receiving the proper amount of nutrients it needs to maintain vision.

Glaucoma: An eye disorder that damages the nerve at the back of the eye (optic nerve), resulting in loss of eyesight, especially peripheral (side) vision. If glaucoma is not treated, loss of vision may continue and lead to blindness.

Legally Blind: Anyone with vision worse than 20/200 that cannot be improved with corrective lenses. In addition, people with a visual field of less than 20 degrees diameter (10 degrees radius) are also considered legally blind.

Low Vision or Visual Impairment: A severe visual impairment that cannot be corrected with conventional glasses or contacts, surgery or medication. Low vision is still usable vision and can be improved with the use of visual aids.

Low Vision Specialist: A trained professional who helps patients use their remaining vision to the fullest potential.

Macula: The small, central portion of the retina.

Macular Degeneration: The leading cause of severe vision loss in people over age 60. It occurs when the small central portion of the retina, known as the macula, deteriorates. Macular degeneration is a type of retinal degenerative disease. There are two forms: “wet” and “dry.”

Macular Hypoplasia: The fovea, a tiny area in the center of the macula region of the retina, the most sensitive area of vision in the retina, fails to fully develop.

Nyctalopia: Loss of night vision.

Nystagmus: Eye movement that cannot be controlled or stopped.

Ophthalmologist: A medical doctor who specializes in eye and vision care. Specially trained to provide the full spectrum of eye care, from prescribing glasses and contact lenses to complex and delicate eye surgery.

Optometrist: Doctors of optometry (ODs) examine, diagnose, treat, and manage diseases, injuries, and disorders of the visual system, the eye, and associated structures as well as identify related systemic conditions affecting the eye. They do not perform surgery.

Optic Nerve: The nerve in the back of the eye that carries the signal from the retina to the brain.

Optic Neuropathy: Loss of the optic nerve function causing loss of central vision, field loss and color vision abnormalities.

Retina: The light-sensitive inner lining of the back of the eye.

Retinitis Pigmentosa (RP): A family of eye diseases that cause gradual deterioration of the retina and can lead to blindness. The most common form of RP follows a progressive pattern: loss of night vision (nyctalopia), loss of side (peripheral) vision and finally, very restricted tunnel vision.

Stargardt’s Disease: The most common form of inherited juvenile macular degeneration that often begins in late childhood and leads to blindness.

Strabismus: When the eyes do not work together. For example, an eye may cross in or turn out.