LASIK is in 2 steps.

The first step involves fashioning a corneal flap. This hinged flap, as shown in the figure, is lifted to expose the inside of the cornea. In the second step, the excimer laser is used to remove corneal tissue selectively, and thereby reshape the cornea to correct the eye’s power.

The figures (1-3) illustrate these steps of LASIK.

Normally, the hinged flap is created using a special instrument known as a microkeratome. This delicate instrument uses an oscillating blade to cut the cornea and create the flap.

While LASIK is a safe procedure, most complications that can occur are due to the use of the microkeratome to create the flap. Since the microkeratome is a mechanical instrument, and a rather delicate one at that, all kinds of problems can occur. These include:

a) Irregular Flaps: Flaps which are not uniformly thick throughout their diameter, and worse, which are too thin or too thick at places.

b) Excessive variation between intended and achieved flap thickness:  Safe LASIK needs a predictable flap thickness. This is not always possible with a microkeratome.

c) Free Caps: