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.
Special thanks to Bryce Carlson for this research.
If you are ready to choose a doctor to be evaluated for conventional
or wavefront custom Lasik, All-Laser Lasik,
PRK,
LASEK,
Epi-Lasik,
NearVision CK,
RLE, or any
refractive surgery procedure, we highly recommend you consider
a doctor who has been evaluated and certified by the USAEyes
nonprofit organization. Locate a USAEyes Evaluated & Certified
Lasik Laser Eye Surgery Doctor.
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