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Epi-Laser vs. IntraLASIK
Three-month post-op visual acuity is better
with Epi-Laser.
Michael J. Endl, MD
Our reliance on surface ablation has been
evolving, predominantly due to heightened concern about corneal ectasia. No
one wants to see an elective surgery patient go on to a potentially
devastating complication - nor do we want to face lawsuits stemming from
post-operative ectasia.
In light of this, I have really taken a
"first, do no harm" approach, greatly expanding the role of surface
ablation.
A few years ago, I was predominantly a
LASIK surgeon, with only about 5%-10% of my cases being surface ablation.
However, once I acquired the Nidek Magellan Mapper corneal topographer, I
saw that close to 30% of my patients had an elevated risk of ectasia. The
Magellan uses artificial intelligence to compare the patient's top-bottom
symmetry to that of normal eyes and identify irregularities. It is also very
good at distinguishing between contact lens-induced changes and keratoconus
patterns, so it may help me consider as candidates some people I would
previously have ruled out for refractive surgery. For any patient flagged by
the Magellan, those with thinner corneas, or patients whose jobs or hobbies
put them at risk of late flap displacement, surface ablation is the safest
choice.
My current LASIK technique is wavefront-guided
ablation using the Alcon CustomCornea system with thin flaps made using the
femtosecond laser. For surface ablation, I have switched from
alcohol-assisted PRK to flapless Epi-Laser with the Moria Epi-K based on
clinical studies I have conducted to determine the best procedure.
In 2005, we retrospectively compared
results from our first 150 eyes treated with Epi-K to a similar number of
PRK eyes. In the Epi-Laser cases, the average flap thickness was very
predictable, at just under 50 µm.
At that time, we were still repositioning the epithelial flap after the
ablation.
We found that Epi-Laser produced
significantly less pain, photophobia, and tearing than PRK in the first four
postoperative days. Beyond the first week, as the epithelial cells
regenerated, there was little difference between the two. Since discomfort
had been the biggest disadvantage of surface ablation, this finding was
sufficient for me to move to Epi-Laser.
Discarding the
flap
Next, we began to question whether the
new "flapless" Epi-Laser could further improve the patient's post-op
experience.
I conducted a small contralateral eye
study (n=13) to compare visual recovery, epithelial regeneration, and
subjective patient experience with and without the epithelial flap. The mean
spherical equivalent was -4.25D. All patients had bilateral same-day surgery
with Alcon CustomCornea and the Moria Epi-K, Mitomycin C (MMC) was used in
98% of the eyes.
On the first day after surgery, not only
did 46% of the patients have better uncorrected acuity in the eye with the
flap removed, but there was a five-line difference between the flapless eye
and the fellow eye. By the one-week visit, all subjects either saw better
with the eye without a flap (73%) or saw equally well with both eyes (27%).
We were twice as likely to be able to remove the bandage contact lens by day
three or four post-op in the eyes in which the flap has been removed.
I expected there to be more pain in the
eyes without the epithelial flap, but that was not the case. On every single
parameter we considered, the flapless group did better. They had
substantially faster visual recovery, faster epithelial regeneration, and
less pain and discomfort in the immediate postop period, with no increase in
haze. We concluded there was no advantage in replacing the epithelial flap.
The Epi-K make a very smooth, clean edge
for the area to be ablated; removal of the epithelial flap eliminates the
devitalized cells that slow down the healing and visual recovery.
Haze prevention is very important, so I
use MMC liberally, especially with deep ablations and people who have
allergies or asthma. My threshold for using MMC prophylactically is also
very low for patients in their early 20s, who tend to have a slightly more
hyperactive immune system. Postoperatively, all patients should wear UV
blocking sunglasses during the first three months to minimize the risk of
haze.
There are also several steps that
surgeons can take to improve comfort and increase patient satisfaction with
Epi-Laser. Some tips for success include pre-treating with Motrin
(ibuprofen, Pharmacia) or similar oral NSAID (unless contraindicated by
history of stomach ulcers, etc.) to help blunt the inflammatory cycle. I
prescribe it tow to six times a day pre- and post-op, base on the patient's
weight. Vitamin C, given pre- and post-operatively, also speeds healing of
the epithelial cells.
Some have suggested using the Acuvue
Oasys contact lens as a bandage lens. Whether you prefer Oasys or a
different contact lens, it should fit tighter than one would choose for
long-term wear. A tight lens with a base curve of 8.3-8.4 will prevent it
from moving around on the eye and causing discomfort. Dilation also helps to
block the ciliary muscle spasm and reduce pain in the immediate postop
period.
With this regimen and the flapless
technique, I'm comfortable enough with Epi-Laser that 40-50% of my patients
have it instead of LASIK.
Comparing
IntraLASIK to Epi-Laser
Most recently, we retrospectively
compared our IntraLASIK and Epi-Laser results. In this study, a broad range
of myopic subjects was treated with wavefront-guided Alcon CustomCornea.
Both treatments were save and effective, but we did see some advantages to
Epi-Laser.
In the LASIK group (160 eyes), the
lamellar flaps were made with the 60-kHz femtosecond laser. In the Epi-Laser
group (58 eyes), the epithelial flaps were make with the Moria Epi-K.
Six-week follow-up was available for all patients; three-month follow-up was
available for 25% of the IntraLASIK eyes and 48% of the Epi-Laser eyes.
The two patient groups were typical of
the refractive surgery population, with a mean age of 35 and mean MRSE of
-4.39 D (LASIK) and -4.33 D (Epi-Laser), although the upper end of the range
for both sphere and cylinder was higher in the LASIK group.
Scatter plots of the attempted-versus-achieved
corrections for both groups showed a slightly wider scatter for the
Epi-Laser group; this difference disappeared by three months. At three
months, in fact, the Epi-Laser results were more accurate, although the
difference was small (Fig 1). We were using a new excimer laser with no
nomogram adjustment, which probably accounted for the slight overcorrection
in both groups.
There was a difference in the binocular
20/20 rates between the two groups. 86% of the Epi-Laser patients, compared
to 71% of the IntraLASIK patients, were 20/20 at 3 months (Fig 2). All
patients in both groups were 20/30 or better.
We also compared post-operative
higher-order aberrations in a subset of 10 eyes from each group. Both
procedures induced some aberrations. Coma and total HOA increased more in
the LASIK group than in the Epi-Laser group (Figs 3-4); trefoil was higher
in the Epi-Laser group. None of the differences was statistically
significant, given the small sample size. Spherical aberration (SA) was
reduced in both groups compared to pre-operative levels (Fig 5). In the
future, I would like to conduct contrast sensitivity and driver simulation
testing to see if the reduction in SA has any meaningful impact on night
vision.
Both Epi-Laser and IntraLASIK are safe
and effective. Patients who are drawn to either of these technologies are
safety conscious. In our practice, they understand they will either get
LASIK or flapless Epi-Laser, depending on the exam results and their
lifestyle. I tell them during the consultation that if I see anything that
concerns me, I am going to recommend Epi-Laser.
When we do choose a surface procedure,
the good news is that our data suggest that at three months post-op,
uncorrected visual acuity with Epi-Laser is better and the aberration
profile is also slightly better than in LASIK cases. In the past, fear of
pain was the biggest hurdle for patients who were not good LASIK candidates,
but today I can assure my Epi-Laser patients that 90% of them will
experience no pain at all. If they are among the 10% who do experience some
discomfort, we can effectively manage it.
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