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By: Gary M. Kawesch, MD - Exclusive
to EyeWorld
The laser-scrape method may have several advantages
over traditional techniques used to remove epithelium
before PRK.
Most surgeons would agree that epithelium removal
in photorefractive keratectomy is one of the procedure's
most critical aspects. Expedient, uniform removal
helps minimize stromal drying, which can increase
the ablation rate and lead to overcorrection.
The scrape technique, using a PRK spatula or
a blade, is widely used. Some surgeons first loosen
the epithelium with alcohol. It is common to remove
peripheral epithelium first, then central epithelium,
to prevent excessive central drying. Unfortunately,
this approach may cause excessive peripheral drying,
which could lead to excessive peripheral tissue
ablation and a steep central island.
The laser-scrape method, which I prefer for myopic
corrections with the Visx Star laser, has several
advantages over other scraping techniques.
 Foremost
is the precise removal of a 6-mm circular area
of epithelium. Not only does this afford quicker
re-epithelialization than a sloppy scrape, which
may go out to 7 mm or beyond, but it also leaves
a very sharp demarcation between stroma and epithelium.
To assist with centration, this boundary may be
aligned with the Visx laser's 6-mm reticle.
Hyperopic PRK treatments necessitate another
epithelium removal technique, the rotating brush.
I use the Amoil's epithelial scrubber. Unfortunately,
the brush has some disadvantages. Visualization
of the cornea is poor, because of the instrument's
nature. The eye may move, and usually needs to
be steadied with a fixation ring. And finally,
it is difficult to remove a precise 9-mm circular
area of epithelium (9 mm is the outermost diameter
of the hyperopic ablation).
Solution is elegant, yet simple
I mark the eye with a 9.5-mm optical zone marker,
custom-made for me by American Surgical Instruments,
Inc. I use my left hand, and keep the marker firmly
in place on the cornea. With my right hand, I
apply the Amoil's brush within the confines of
the optical zone marker. Using firm pressure and
a gentle rotating motion, all epithelium within
the marker's confines is removed in about 3 seconds.
The demarcation between stroma and epithelium
is as clean as the 6-mm optical zone demarcation
seen with the laser-scrape technique. A PRK spatula
is then used to quickly clean any debris from
the stromal surface before the ablation begins.
 The
optical zone marker is high profile, to minimize
the chance of bristles escaping its confines.
There are no crosshairs and the marker's bevel
is on the outer surface.
In my experience, this technique has proven superior
to the brush-only technique. In fact, surgeons
using the brush for myopic ablations may want
to adopt the technique, using a 7.5- or 8-mm optical
zone marker, which is readily available from several
manufacturers.
Gary M. Kawesch, MD, has no financial interest
in any of the products mentioned.
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