LASIK Laser Eye Surgery Articles from
San Francisco Vision Specialist Dr. Gary Kawesch

A New Technique for Pre-PRK Epithelium Removal
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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