Glossary

  • Rod Cell

    A photoreceptor cell responsible for black and white, night and peripheral (side) vision.

    A rod cell is a rod-shaped photoreceptor cell that is located throughout the retina but is more common outside of the central macular region of the retina (i.e., is found in the periphery of the retina). The rod cell is particularly important for black and white, night and peripheral (side) vision. In many forms of RP, rod cell loss leads to what is sometimes referred to as "tunnel vision."

  • Sclera

    The tough, outer, protective shell of the eye.

    The sclera, also called the "white of the eye" is the tough outer protective shell of the eye. If the eye is like a camera, consider the sclera to be like the camera body.

  • Sex Chromosomes

    The chromosomes inherited from both parents that contain the genetic material that determines the sex of an individual. X-linked diseases are caused by mutations of genes on the X chromosome.

  • Stargardt Disease

    Stargardt disease is the most common form of inherited juvenile macular degeneration. The progressive vision loss associated with Stargardt disease is caused by the death of photoreceptor cells in the central portion of the retina called the macula.

  • Stem Cell

    A self-renewing, unspecialized cell that is capabile of becoming any one of a number of more specialized cells.

  • Strabismus

    A misalignment of the eyes (pointing in and/or out). This situation may be due to eye muscle problems.

    A misalignment of the eyes in which each eye, simultaneously can point in a different direction. Crossed eyes (esotropia) are one type of strabismus; "wall-eyes" (exotropia) are another. The exact cause is unknown, but it appears to be a problem with the eye muscles. Strabismus can affect depth perception.

  • Ultraviolet (UV) light

    A radiant component of sunlight, invisible to the eye, that is characterized by short wavelengths and high energy. It will damage the retina (as well as the skin) with lengthy, unprotected exposure. If you use nutritional supplementation, please consult with your personal physician and ophthalmologist as your personal health situation may require monitoring or a non-typical approach and nutritional supplements may interfere with prescribed medicines.

  • Usher Syndrome

    Usher syndrome is an inherited condition characterized by hearing impairment and progressive vision loss. Balance may also be affected. Symptoms vary from person to person and progress at different rates.

    There are at least three different forms of Usher syndrome. People with Usher syndrome type 1 (USH1) are born completely deaf and experience problems with balance. The first signs of RP - night blindness and loss of peripheral vision - usually appear in early adolescence.

  • Vector

    The "vehicle" or carrier for delivering genes or genetic information into the cell, particularly useful for gene therapy.

  • VEGF (Vascular Endothelial Growth Factor)

    A class of proteins that causes new blood vessel growth (angiogenesis) and maintains the natural "leakiness" inherent in vessels. These are normal body functions, which, if they happen where they shouldn't (such as in the retina), can cause disease, such as AMD.

  • Visual Acuity

    A measure of the ability to distinguish fine visual details.

    Visual acuity is the clarity of vision held by an individual and is measured as a fraction of normal vision: 20/20 vision indicates an eye that sees at 20 feet what a normal, "standard" eye should see at 20 feet; 20/400 vision indicates an eye that sees at 20 feet what a normal eye sees at 400 feet. Usually measured with a letter chart (Snellen), it can also be measured using pictures, black and white lines or visual evoked potentials.

  • Visual Field

    The entire area that the eye can see from side to side without physically moving the eyes or head (includes peripheral vision).

    The portion of the environment that the eye sees, on fixed forward gaze, includes the entire field of vision (central and peripheral) and is measured by a perimetry test. The normal field of vision is about 140 degrees for each eye (monocular vision) and about 180 degrees for both eyes (binocular vision).

  • Vitamin C (Ascorbic Acid)

    An anti-oxidant found in certain fruits and vegetables (and as a commercial supplement) that is used as part of a nutritional treatment of AMD.

  • Vitamin E

    An anti-oxidant found in certain oils, nuts, and other foods (and as a commercial supplement) that is also used as part of a nutritional treatment of AMD.

  • Vitreous

    The clear, jelly-like substance found in the middle of the eye that helps to regulate eye pressure and shape.

    The vitreous is the clear, jelly-like substance found in the middle of the eye that helps to regulate eye pressure and shape. Light must pass through the vitreous to fall upon the retina, so it must be as transparent as possible to avoid vision distortion or disruption.

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