Glossary

astigmatism

A term used to describe the shape of the cornea. With astigmatism the cornea is more curved in one direction like a football, instead of round like a basketball and often occurs with nearsightedness or farsightedness. This causes light to focus on more than one point resulting in blurry and distorted vision.

cornea

The clear, avascular cornea tissue acts as the window of the eye. It provides two-thirds of the refractive power of the eye.

diopter

A unit of measurement used by eye doctors and opticians to communicate the degree of refractive error with respect to nearsightedness, farsightedness, and astigmatism.

excimer laser

A high-energy, cold laser that is used to reshape or sculpt the cornea surface to change the refractive power of the cornea.

hyperopia

The medical term for the refractive error known as farsightedness. It is a condition where the eye is shorter than usual or the cornea and lens lack the focusing power needed so that images are in contact with the retina before coming into sharp focus, causing the near vision to appear blurred.

LASIK:

A type of refractive eye surgery. It stands for laser assisted in situ keratomileusis. The procedure combines the use of an instrument known as a microkeratome to create a flap across the front surface of the cornea, and the excimer laser to remove the tissue from the exposed surface.

myopia

The medical term for the refractive error known as nearsightedness. It is a condition where the eye is longer than usual or the cornea and lens have too much focusing power. In this condition images are in focus in front of the retina causing blurred distance vision.

PRK

The refractive procedure known as photorefractive keratectomy. A high-powered, computer-controlled beam of ultraviolet light is used to sculpt the cornea surface.

PTK

A therapeutic use of the excimer laser known as phototherapeutic keratectomy to treat superficial corneal scars, opacities, and smooth irregularities. May help to eliminate or delay the need to have a corneal transplant.

presbyopia

A natural aging of the eye when the lens begins to lose its elasticity, making it difficult to focus on close objects. Bifocals or reading glasses are needed to correct this refractive error which typically begins around age 40. There currently are no approved refractive surgery procedures to correct this condition.

RK

The refractive procedure known as radial keratotomy. A calibrated diamond blade is used to make radial incisions in the cornea to reduce low levels of myopia.