IN-VIVO CONFOCAL MICROSCOPY AFTER PHOTOREFRACTIVE KERATECTOMY IN HUMANS - A PROSPECTIVE, LONG-TERM STUDY

Objective: To assess corneal morphological characteristics in vivo aft er photorefractive keratectomy (PRK) in humans. Methods: Eighteen eyes were examined before and after PRK by means of in vivo confocal micro scopy. Epithelial, stromal, and endothelial morphological characterist ics were recorded. Minimum follow-up was 12 months. Results: Immediate ly after PRK, the anterior stroma showed marked intercellular edema. A t 1 month, fine linear structures were noted in the anterior stroma an d midstroma, and a thin hyperreflective scar was present. The linear s tructures and the scar tissue were more marked at 4 months but were st ill present up to 26 months. Anterior stromal keratocyte density incre ased significantly 1 and 4 months after PRK, whereas midstromal and po sterior keratocytes and endothelial cell densities did not change. Bas al epithelial nerves were recognizable as early as 1 month after PRK. Contact lens-related microdots in the stroma remained unaffected. Conc lusions: The stromal linear structures represent a finding that is det ectable only by confocal microscopy at high magnification, is not rela ted to previous contact lens wear, and is still visible 26 months afte r PRK. The extension of these structures as far as the midstroma indic ates that the permanent corneal changes caused by PRK affect deeper st romal layers than the immediate subepithelial region.