Glossary of AMD Terms

Age-Related Macular Degeneration (AMD): A degenerative eye disease that causes loss of central vision.

Amsler Grid: A chart resembling graph paper used in some cases to detect central visual field distortions symptomatic of AMD.

Angiogenesis: The formation of new blood vessels.

Antioxidants: Micronutrients that combat the stimulation of abnormal cellular reproduction (cancer) and cellular destruction (aging).

Aqueous Humor: Fluid contained in the anterior and posterior chambers of the eye.

Carotenoids: Family of vitamins including beta-carotene, lutein and zeaxanthin, believed to serve as antioxidants and reduce abnormal cell formation or degeneration of normal cells.

Choroid: Vascular layer of the eye lying between the retina and the sclera, it provides nourishment to outer layers of the retina.

Choroidal Neovascularization (CNV): Abnormal formation of new blood vessels under the retina. CNV in AMD is characterized by one of three locations: subfoveal, (lies directly below the fovea); juxtafoveal; and extrafoveal (lying progressively further away from the center of the macula).

Cornea: The transparent tissue that covers the iris and pupil at the front of the eye and helps focus incoming light.

Diode: A type of laser used for treatment of wet macular degeneration.

Drusen: Tiny, white or yellow, hyaline (clear, glassy like) deposits lying beneath the retinal pigment epithelium (RPE).

Dry AMD (Non-exudative or non-neovascular AMD): Accumulation of drusen and/or thinning and loss of retinal pigment epithelial cells.

Fluorescein Angiography: A photographic imaging test used to detect the composition, size and location of CNV. Vegetable dye is injected into a vein, and then circulates within the eye allowing photographs of the intraocular circulation to be recorded.

Fovea: Central pit in the macula that produces sharpest vision. The location of CNV (blood vessels) under or near the center of the fovea impacts the success of laser treatments of wet AMD.

Iris: Pigmented tissue lying behind the cornea that gives color to the eye (e.g., blue or brown eyes) and contracts or expands to let more or less light into the eye through the pupil.

Laser: A very narrow, high intensity light, which can burn tissue, activate light-sensitive dyes, or join structures together.

Legal Blindness: The definition for legal blindness may vary among countries. Millions of people have partial or complete loss of vision in Canada, where normal vision is defined as 20/20 and legal blindness is defined as worse than or equal to 20/200 with best correction in the better eye or a visual field extent of less than 20 degrees in diameter. In Canada, a visual acuity worse than 20/50 disqualifies people from obtaining a driver?s license or restricts their driving to daytime only, as do some visual field deficits.

Lens: The clear biconvex (curved on both sides) lens of the eye helps focus light through the vitreous to the retina.

Macula: The small central layer of tissue in the retina, responsible for central vision.

Neovascularization: Abnormal formation of new blood vessels usually on or under the retina.

Ophthalmologist: An eye-care specialist who graduated medical school followed by one year of general medical/surgical internship and three to four years of additional residency training in the refractive, medical and surgical treatment of eye diseases.

Ophthalmoscope: An instrument used to examine the internal structures of the eye by an illumination and magnification system.

Optic Nerve: The largest sensory nerve of the brain, it carries visual information from the retina to the brain.

Optometrist: An eye-care specialist who went to a university based professional optometry school for four years of training in the diagnosis and treatment of eye diseases.

Photocoagulation: A surgical procedure involving the application of intense light to burn or destroy selected intraocular structures such as abnormal blood vessels and tumors.

Photodynamic Therapy (PDT): The use of a light activated drug together with a cold (low energy)-laser treatment to close blood vessels found in wet AMD.

Photoreceptor: A nerve end-organ or receptor sensitive to light.

Pupil: The variable-sized black circular opening in the center of the iris regulating the amount of light that enters the eye.

Retina: The lining of the rear two-thirds of the eye, it converts images from the eye?s optical system into electrical impulses sent along the optic nerve to the brain.

Retinal Pigment Epithelium (RPE): Pigment cell layer just outside the retina that nourishes retinal visual cells; it is firmly attached to underlying choroid and overlying retinal visual cells and composed of one layer of cells that are densely packed with pigment granules.

Sclera: Opaque, fibrous, protective outer layer of the eye ("white of the eye") that is directly continuous with the cornea in front and with the sheath covering optic nerve behind.

Scotoma: An area of partial or complete loss of vision surrounded by an area of normal vision, which can occur in advanced AMD.

Vascular Endothelial Growth Factor (VEGF): Protein produced by the RPE thought to promote excessive CNV formation.

Visual Acuity: The clearness of vision that depends upon the sharpness of the retinal image.

Visual Field: The complete area of vision that includes what is seen above, below, to the sides and in the center. There is a central visual field that is directly in front of us, and a peripheral visual field that we perceive in our "side" vision.

Vitreous: Transparent, colorless gel that fills the rear two-thirds of the interior of the eyeball, between the lens and the retina.

Wet AMD (Exudative or Neovascular AMD): Caused by the growth of CNV under the macula. The leaky blood vessels cause distortion and loss of central vision.

Source: AMD Alliance International