glaucoma: a disease in which the optic nerve becomes damaged. This is most often caused by an elevated pressure inside the eye (intraocular pressure) due to the build up of a liquid substance called the aqueous humor. This condition is the leading cause of blindness among African-Americans.
high index: a term used to describe a type of spectacle lens that has a higher index of refraction than standard glass or plastic lenses. Because theses lenses are more dense than standard glass or plastic, light rays pass more quickly through the lens to the eye and do so with less material (i.e. thinner, lighter lenses).
hyperopia: farsightedness; vision of nearby objects is impaired, while distance objects remain in relative focus. Light is focused on a point that lies behind the retina.
iris: the muscular diaphragm that controls the size of the pupil. The iris itself is NOT responsible for eye color, but rather allows the pigmentation of the choroid (a layer beneath the sclera or white portion of the eye) to be visible.
keratoconus: a progressive thinning of the cornea which results in a cone-shaped bulge that causes blurry or distorted vision. This condition may result from heredity, injury, or certain eye or other diseases. Usually the cornea heals and regains stability without causing severe visual impairment, but in few instances the cornea will gradually deteriorate and require a corneal transplant.
LASIK: Laser-Assisted In Situ Keratomileusis; a type of refractive surgery in which a thin layer of corneal tissue is removed via laser to correct certain degrees of myopia.
lens: transparent structure within the eye that focuses light rays upon the retina.
