LASIK involves the creation of a superficial partial thickness corneal flap (see figure). The flap is created with a "microkeratome", a specilaised highly refined instrument which uses an oscillating blade.

Laser is performed underneath the flap, and then the flap is replaced.

The disadvantage compared to ASA is that it is a slightly more complicated and invasive procedure.

A thick and very regular cornea is required for this technique.