Before the appearance of computers and lasers, the main tools available to an ophthalmologist were a scalpel, a steady hand, and some engineering knowledge. The premise was that if the doctor could modify the shape of the cornea, then he or she could make a permanent improvement in a patient’s vision.

With RK, the doctor uses a diamond-bladed instrument to make incisions in the cornea. The incisions are made in a spoke-like pattern which allow the eye to flatten so vision becomes clearer.

Unfortunately, RK has some limitations and drawbacks. The main drawback is that the incisions can weaken the cornea and, over time, the cornea continues to change shape.

Although RK continues to be used in special cases, it has declined in use since the introduction of PRK.