Corneal repair following keratectomy. A comparison between conventional surgery and laser photoablation

We have used the fluorescent dye dichlorotriazinyl aminofluorescein (DTAF) to demonstrate corneal remodeling following keratectomy in the rabbit. The dye was applied to the surface of 3.5 mm diameter anterior keratectomy wounds produced by either lamellar dissection or photoablation with an excimer laser (193 nm) to a depth of 15, 50 or 75 microns. Stromal wounds that had been ablated in 12 concentric steps to produce a graded profile with a central depth of 15 or 30 microns were also studied. The repair process was followed for periods of up to 6 months. These results were compared to wounds of similar dimensions in which an intrastromal keratectomy was performed and the anterior stromal surface replaced. Sections examined by fluorescence microscopy showed that connective tissue was deposited beneath the epithelium of all anterior keratectomy wounds irrespective of their mode of induction or depth. The deposition of this new tissue, and an associated thickening of the epithelium over the wound surface, appeared to be complete by 1 month and tended to restore the original surface contour. The synthesis of connective tissue, but not the hyperplasia of the epithelium, was reduced by local steroid treatment. In contrast, an intrastromal keratectomy only stimulated the deposition of small amounts of new connective tissue at the wound junction without as marked a thickening of the overlying epithelium. These observations emphasize the importance of the epithelium in moderating repair after stromal loss, and suggest that remodeling may result in corneal haze and a change in the desired refraction if refractive surgery is attempted by anterior keratectomy.