Glossary of Vision & Contact Lens Terms

astigmatism: a form of defective vision resulting from incorrect curvature of the cornea. This causes light to scatter rather than focus into a single point on the retina, which in turn creates blurred vision.

color tint: a significant tint added to a contact lens in order to change the apparent color of the wearer's eye.

contact lens: a roughly hemispherical sheet of plastic sometimes worn against the cornea. Contact lenses are inserted to help clarify defective vision.

cornea: a thin transparent coating of the iris and sclera.

enhancement tint: a slight tint added to a contact lens in order to intensify the wearer's natural eye color.

hyperopia: a form of defective vision in which light rays are brought to a focus behind the retina of the eye, which results in headaches, eyestrain, and/or blurred vision of nearby objects. Also known as "far-sightedness."

iris: the colored part of the eye.

lasik: or "laser-assisted in-situ keratomileusis," a surgical procedure in which a tiny flap is cut into the cornea, the tissue underneath is trimmed by laser, and the flap is closed shut. Lasik corrects astigmatism, hyperopia, and myopia.

lens: the part of the eye that focuses light onto the retina.

light-filtering lens: a tint added to an athlete or sportsman's contact lens that intensifies one specific color (e.g., the yellow of a tennis ball) while muting all surrounding colors.

locator tint: see "visibility tint."

myopia: a form of defective vision in which light rays are brought to a focus ahead of the retina of the eye, which results in headaches, eyestrain, and/or blurred vision of distant objects. Also known as "near-sightedness."

phosphorylcholine (PC): a substance found naturally in the membranes surrounding human cells. PC attracts water and is used to help lubricate certain brands of contact lens.

plano: a contact lens shaped for normal eyes, i.e., spherical curvature for eye care patients who are neither near-sighted nor far-sighted.

polymethylmethacrylate (PMMA): the rigid plastic material used to make hard contact lenses.

presbyopia: a condition in which the eye of an elderly person is unable to focus on nearby objects. This condition typically sets in around age 40. Additional symptoms may include eyestrain, headaches and/or squinting.

pupil: the black, circular aperture in the eye that admits light to the retina.

retina: the thin tissue at the back of the eye that receives an image formed by the lens and converts it into electrical impulses, which are then carried to the brain by the optic nerve.

saline (solution): aterile salt water used to clean and store soft contact lenses.

sclera: the white part of the eye.

toric lens: a lens that has been shaped in such a way as to correct astigmatism.

visibility tint: a very slight blue or green tint added to a contact lens in order to help the wearer see it after losing it. A locator tint is invisible once the lens has been reinserted into the eye.