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Department of Ophthalmology PRK  The laser treatment can be applied to the surface of the cornea after gently removing the layer of surface cells which covers it. Termed PRK, this was the first type of refractive surgery performed in the US with the excimer laser. Still an excellent option for lower degrees of treatment or for those with thin corneas who cannot spare the tissue for flap creation, PRK offers the advantage of no potential for flap complications as no flap is created. Preferred by the military for resistence to trauma, advances in laser technology have also optimized PRK outcomes. The disadvantage to PRK has always been slower recovery as vision remains blurry until the surface cells heal and smooth, usually within several weeks.
A variation on the PRK technique called LASEK utilizes a dilute solution of alcohol to loosen the surface cells as a sheet which can then be replaced under a bandage contact lens to speed healing. Another advance which is pushing the frontiers of PRK is the use of an antiscaring medication called mitomycin, which allows higher degrees of correction without inducing a scarring response. No Flap: The procedure eliminates the surgical step of flap creation and thus eliminates the possibility of flap complications. Recent reports have documented that flap creation induces a small amount of optical irregularity which is of course avoided with PRK. Better for some facial and eyelid configurations which will make the microkeratome difficult to use. Greater Trauma Resistance: PRK may be preferable for those with occupations or avocations in which trauma to the eye is a possibility such as law officers, military personnel, martial artists, etc. For those who suffer form recurrent breakdown of the corneal surface, PRK is a better procedure. Better for thin corneas: If too much corneal tissue is removed, the cornea may become structurally weakened and bow forward (ectasia). By not creating a flap, more tissue is preserved for laser treatment thus not weakening the cornea. LASEK (Laser-assisted subepithelial keratectomy) A variant on the PRK procedure, this technique loosens the surface cells with a dilute alcohol solution allowing the sheet of cells to be displaced then repositioned over the treatment site. This method can reduce the time required for the surface cells to heal. A bandage contact lens is still used as in PRK. Studies have verified that a substantial percentage of surface cells remain viable in the flap of epithelial tissue. It remains to be determined whether there is any less superficial haze or regression for patients with higher myopic corrections. Until more information is available, we prefer to select candidates for LASEK according to the same criteria as the PRK procedure. |
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