Undercorrection
A complication of refractive surgery where the achieved amount of correction is less than desired.

Visual Acuity
The clearness of vision; the ability to distinguish details and shapes.

Overcorrection
A complication of refractive surgery where the achieved amount of correction is more than desired.

Kerato
Prefix indicating relationship to the cornea.

Keratotomy
A surgical incision (cut) of the cornea.

Farsightedness
The common term for hyperopia.

PRK
The acronym for photorefractive keratectomy which is a procedure involving the removal of the surface layer of the cornea (epithelium) by gentle scraping and use of a computer-controlled excimer laser to reshape the stroma.

Snellen Visual Acuity Chart
One of many charts used to measure vision.

Epithelium
The outermost layer of cells of the cornea and the eye's first defense against infection.

FDA
The abbreviation for the Food and Drug Administration. It is the United States governmental agency responsible for the evaluation and approval of medical devices.