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By: Gary M. Kawesch, MD - Exclusive
to EyeWorld
Phototherapeutic keratectomy is a valuable technique
for treating corneal opacities, but its usefulness
is limited to the anterior cornea. Traditionally,
deeper scars have required lamellar or penetrating
keratoplasty. I recently had an interesting case.
A 26-year-old patient underwent hyperopic automated
lamellar keratoplasty in September 1994, by another
surgeon. His preoperative refraction was +4 +1.25
x60 right eye and +3.5 +3 x107 left eye, with
best-corrected acuity of 20/20 in each eye. Surgery
in the left eye was uneventful, but in the right
eye the surgeon created a free cap, inadvertently
replaced it inside-out (epithelium against stromal
bed) and sutured it in place. Four days later,
the surgeon realized his error when the free cap
would not epithelialize well; he took the patient
back to the operating room, removed the cap and
replaced it properly. I first saw the patient
for a second-opinion consultation several days
after this second surgery. I noted extensive epithelial
ingrowth, and recommended immediate removal, which
was performed without incident.
After 6 months, the patient had uncorrected vision
of 20/60 in the right eye, and with a refraction
of +2 +3.75 x75, corrected only to 20/50. A dense
haze was noted in the interface, and keratometric
mires were distorted. The patient underwent a
traditional surface excimer PTK in July 1995 at
the Jules Stein Eye Institute, University of California,
Los Angeles, but had no improvement in best-corrected
vision. A trial of a rigid gas-permeable contact
lens provided vision of only 20/50. Pinhole acuity
was no better. The patient understood his only
traditional option to rehabilitate vision would
be lamellar or penetrating keratoplasty. I discussed
with the patient a unique, but completely unproven,
technique to improve his vision. If it failed,
keratoplasty could still be performed. The proposed
procedure was an intrastromal PTK. A deep keratectomy
would be performed using the Chiron Automated
Corneal Shaper, creating a flap to access the
plane of scarring. An excimer laser, using PTK
mode with a beam diameter of cleared 5 mm, would
then be used to ablate the stromal bed and the
undersurface of the flap.
I performed this procedure in April
1996 with a 400-,um plate and a 5.6-mm lens, setting
the keratome stop to leave a very small hinge.
Eleven microns of tissue were ablated from the
bed and 7 um from the flap's undersurface. The
flap was replaced without sutures. Five days postop,
he was 20/2' uncorrected, refracting to 20/20
with +1.25 +1 x120. Two months postop, he was
20/30+, refracting 20/25 with +1.5 sphere. Postoperative
slit lamp photographs reveal a clearing of much
of the central, deep haze.
Iatrogenic keratoconus secondary to a deep lamellar
cut, or hyperopic shift secondary to laser photoablation,
are concerns with this approach, but a good result
will save the patient from needing a much more
invasive technique.
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