What is Advanced Surface Ablation?
Advanced Surface Ablation is removing the epithelium from the cornea and treating the refractive error on the front surface of the cornea. I use a VISX laser and my comments relate to the VISX laser.
The epithelium can be removed several ways. The oldest method is to scrape the epithelium off with a blade. The disadvantage with this method is that there may be incomplete removal of the epithelium and damage to Bowman’s membrane (the layer just below the epithelium).
A second method is removal of the epithelium with the laser. This treatment parameter only allows the epithelium to be removed to 6 mm and now the new treatment zone extends to 8 mm. Enlargement of the treatment zone reduces the night vision symptoms.
A third method of epithelial removal is Epilasik. With this method a suction device is placed on the eye to hold it, and a blunt blade is used to remove the epithelium in a sheet. The sheet is replaced after the Excimer laser treatment.
A fourth method is the use of alcohol. A dilute solution is used on the eye in a 9 mm holding cup for 30 seconds. Dilute alcohol loosens the epithelium so it can be moved to one side or totally removed, in preparation for the Excimer laser treatment.
With all four of these methods, a contact lens should be worn on the eye after the surgery to allow the epithelium to regenerate. All of these techniques have more pain than LASIK. All of these techniques have a slower return of vision than LASIK.
There are three advantages to these techniques over LASIK. The first is that it is a safer procedure. Cutting a flap weakens the cornea and with treatment, tissue is removed and the cornea is further thinned. Thus, Advanced Surface Ablation is safer than LASIK. The second advantage is that the complication rate is less. LASIK has complications from bad flaps, slipped flaps, diffuse lamellar keratitis and epithelial ingrowth. The third advantage is that when a “finger-print” of the eye (i.e., wavescan) is performed before surgery, the laser can treat all these components. When a LASIK flap is cut, higher order aberrations (horizontal coma) can occur. Since these occur after the wavescan test was performed, these abnormalities are not figured into the treatment plan. Thus, Advanced Surface Ablation is safer and more accurate.