Confocal microscopy changes in epithelial and stromal thickness up to 7 years after LASIK and photorefractive keratectomy for myopia

PURPOSE: To determine the long-term changes in epithelial, stromal, and corneal thickness after LASIK and photorefractive keratectomy (PRK). METHODS: In two prospective observational case series, 11 patients (16 eyes) received LASIK and 12 patients (18 eyes) received PRK to correct myopia or myopic astigmatism. None of the corneas had retreatment procedures. Corneas were examined using confocal microscopy before and at 1 month, and at 1, 2, 3, 5, and 7 years after surgery. Central thicknesses were measured from reflected light intensity profiles recorded by confocal microscopy. Postoperative epithelial thickness was compared to preoperative, and postoperative stromal and corneal thicknesses were compared to thickness at 1 month after surgery. RESULTS: In LASIK, epithelial thickness at 1 month (51±4 μm, n=11) was greater than before surgery (41±4 μm, n=16; P<.001) and remained thicker through 7 years (52±6 μm, n=13; P<.001). Stromal and corneal thickness did not change between 1 month and 7 years after LASIK. After PRK, corneal thickness at 1 year (464±44 μm, n=17) was greater than at 1 month (442±39 μm, n=15; P=.001) and remained thicker at 7 years after PRK (471±45 μm, n=17; P<.001). CONCLUSIONS: The early increase in central epithelial thickness after myopic LASIK persists for at least 7 years and is probably the result of epithelial hyperplasia. Central corneal thickness increases during the first year after PRK and remains stable thereafter up to 7 years.