Dispelling the Myths - Corneal flap healing

If you've done any research on this subject on the internet you've no doubt come across some very scary information. "The flap never heals", "your vision will regress", "lasik suicides", etc. I decided to research each of these claims prior to my surgery and will post my findings. I determined that the majority of this information is meant simply to scare people. Period. I joked with my wife that it was a conspiracy by a group of ophthalmologists who want to scare people so they can keep selling glasses and contacts. ;)

Myth #1: "The flap never heals"

Quite simply, yes it does! It happens in stages and continues over a long time but yes it does eventually heal completely.

Quoted from http://www.usaeyes.org/lasik/faq/lasik-flap-heal.htm:

Many potential and post-conventional or wavefront custom Lasik and All-Laser Lasik patients are concerned about the degree to which the flap ultimately heals and re-bonds to the underlying stromal bed. Here is a synopsis of current thinking on the subject. Of course, due to individual healing differences, the time-line below will vary from person to person.

Hopefully this information reassures some of you that the flap eventually does heal quite securely, and does not just lie there flapping in the breeze, indefinitely. If you still have doubt, remember that corneal transplants, despite being much more invasive than Lasik flaps and consisting of imperfectly cross-matched cadaver tissue, ultimately heal so completely that they provide strength and structural integrity for the eye. This is additional evidence that Lasik flaps do heal very securely and eventually contribute at least to some degree to the bio-mechanical strength of the cornea.

The process of flap healing is similar if the flap is created with a mechanical microkeratome or a laser microkeratome (All-Laser Lasik).

Phase I

Days 1 to 3 post-op Immediately post-op as the flap is re-positioned and the doctor "squeegees" out excess moisture under the flap, a negative osmotic pressure is created that "sucks" the flap onto the stromal bed and holds it there. The flap is held in place fairly well at this time, barring physical trauma such as rubbing the eye or a poke in the eye. Of course, this is a very vulnerable period because any trauma to the flap could easily dislodge it, hence the importance of wearing eye shields at night and similar protections.

Phase II

Days 4 to 14 post-op During this period the epithelium re-generates along the perimeter of the flap, sealing and bonding the flap more securely in place. This is still a vulnerable time, but less so than in Phase I, where only osmotic pressure secured the flap.

Phase III

Days 15 to 60 post-op During this period the re-generated perimeter epithelium lays down a basement membrane that firmly adheres the newly regenerated epithelium to the underlying stromal bed.

Phase IV

Days 61 to 180 post-op During this period the keratocyte cells of the stromal bed and the flap produce an adhesive protein (glycos-aminoglycan) that bonds or "glues" the flap to the stromal bed. By the 180th day, these processes have generally rather strongly secured the flap to the stromal bed. Trauma or surgical instruments can still dislodge or lift the flap, but a good deal of healing and re-bonding of the flap to the stromal bed has occurred.

Phase V

Day 181 to 24+ months post-op During this period collagen slowly begins to form at the interface between the flap and the underlying stromal bed. This collagen includes fibril infiltrates that extend from the flap into the stromal bed, in effect suturing the flap to the underlying stromal bed. At the conclusion of this process the flap is both "glued" and "stitched" into place, as well as "sealed" and secured by the surface perimeter epithelium and basement membrane. Although still not as strong as an untouched cornea of the same thickness, the flap and stromal bed are nevertheless now very securely bonded together. At this time, any trauma strong enough to dislodge the flap would also do damage to an eye without Lasik. It is also believed by many researchers that by the 24th month post-op the flap has begun to contribute to some degree to the bio-mechanical strength of the cornea thus reducing the risk of late-onset ectasia.

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