THE LASIK FLAP
The eye surgeon starts the LASIK procedure by making a flap in the cornea. Many people become anxious when they hear this, because they don’t like the idea of surgery in the delicate tissues of their outer eye. I can understand that feeling, but I want you to understand that this “flap approach” to surgery is a wonderful thing because it results in very rapid healing. The flap includes the epithelium, the outer layer of the cornea, and part of the underlying stroma, the middle, fibrous layer of the cornea. The epithelium is basically a clear skin over the eye. The epithelium has a huge number of nerves, more than any other part of your body. When the epithelium is injured, it hurts. Perhaps you’ve had a corneal abrasion from a contact lens or from trauma. If so, you know how painful an injury to the epithelium is.
When we make a flap on your eye, we lift the epithelium intact. When the flap is replaced at the end of the LASIK procedure, the epithelium is then replaced uninjured. This has great advantages: within a couple of hours your eyes are quite comfortable, and your vision is excellent in a few hours, too. And, as mentioned, using the flap approach means a very fast recovery.
There are two ways to make the flap. Traditionally, the flap was made with a specialized knife called a microkeratome. In concept, the microkeratome is similar to a deli meat slicer, with a vibrating cutting blade and a slot through which the flap emerges. The microkeratome is a reasonable way to make a LASIK flap, but it has two limitations. The first limitation is that the flap is not of uniform thickness. This may result in a less precise correction afterward. The second limitation is that occasionally the microkeratome can cut a hole through the flap. This complication requires terminating the LASIK procedure. The better way to make the flap is with all-laser LASIK.
All-Laser Lasik
