During the healing process, a number of factors occur that allow the corneal flap to stick back onto the eye.
- The corneal flap made during the LASIK procedure is able to lay flat and aligned for 2 reasons:
The corneal flap is created with a superiorly located hinge. When the flap is laid back down (after the procedure is completed), this hinge allows the flap to remain attached and aligned.
When the corneal flap is created, a trough (the "bed") is created in the cornea which is the exact same size as the flap. A flap that is replaced properly will lie perfectly in this trough. This is more stable than a contact lens which sits on top of the cornea and moves with each blink.
- The Hinge:
- The sequence of events for corneal flap adherence is as follows:
During the first few seconds to the first few hours after surgery, the corneal flap begins to stick with the help of negative suction pressure exerted by the cornea. This is the same suction that allows contact lenses to stick to your eyes.
If the eye is too dry during this time, the eyelid can spontaneously stick to the flap. Friction with the surface can cause the flap to move. This can occur in about 0.1-0.5% of patients. For this reason, it is important that patients ensure that their eyes are well lubricated with artificial tears. Hitting the flap can also gently move it. This is why it is important not to rub your eyes after surgery.
During the first few minutes and up to 24 hours after the surgery, the surface epithelium (the transparent surface skin) grows over the incision and seals the flap. Simple lid contact with the flap should not move a flap with sealed epithelium. Moderately hitting the flap (with a finger, mascara, or a drop bottle) will move it.
Cornea stromal scarring:
Finally, after a few weeks to a few months, a scar begins to form around the edge of the flap. This results in the flap being well sealed. Only a severe blow (punch, squash ball) can now move the flap. After 6 months, surgical instruments are required to move a flap.
- Negative suction: