PRK is an outpatient
procedure generally performed with local anesthetic eye drops.
This type of refractive surgery gently reshapes the cornea by
removing microscopic amounts of tissue from the outer surface
with a cool, computer-controlled ultravioletbeam of light. The
beam is so precise it can cut notches in a strand of human hair
without breaking it, and each pulse can remove 39 millionths
of an inch of tissue in 12 billionths of a second. The procedure
itself takes only a few minutes, and patients are typically back
to daily routines in one to three days.
Before the procedure
begins, the patient's eye is measured to determine the degree
of visual problem, and a map of the eye's surface is constructed.
The required corneal change is calculated based on this information,
and then entered into the laser's computer.
Since 1995, a limited
number of laser systems has been approved by FDA to treat various
refractive errors, both with PRK and LASIK.
