glossary

Also known as Dyschromotopsia. A general term for color vision abnormalities. Heritable dyschromatopsias include red (protan), green (deutan), and blue (tritan) color vision deficits. These deficits may be partial (-omaly) or complete (-opia). Red and green color vision defects are X-linked while loss of the blue receptor (tritanopia) is inherited in an autosomal recessive fashion. Also see: Protanomalous Decreased ability to determine differences between colors, especially shades of red and green. Usually hereditary.

A redundant folds in the conjunctiva typically located between the globe and the lower eyelid. Loose bulbar conjunctiva that may become pinched between the lids and cause tearing and inflammation. Frequently age-related. Usually found along the lower lid margin. It interferes with the normal distribution of tears causing dry eye and epiphora.

Structural defects of the eye in which the light rays from a viewed object do not meet in a single focal point, resulting in blurred images being sent to the brain. An astigmatic cornea is not perfectly rounded like a basketball but has an irregular shape more like the side of a football. Astigmatism is most often combined with myopia or hyperopia . A difference in the focal point of the eye in one meridian from another (eg between the horizontal and vertical planes). It can usually be corrected with a cylindrical (toric) lens. An irregularity in the curvature of the cornea, resulting in unequal blur in the two principle meridians. A Refractive Error of the eye in which refractive power is not uniform in all directions (meridians). Light rays entering the eye are refracted unequally through different meridians, which prevents formation of a sharp image focus on the retina. Correctable with a cylindrical lens.