PURPOSE: To investigate the incidence of epithelial ingrowth after laser in situ keratomileusis (LASIK) using the VISX 20/20B and VISX Star S3 laser systems. METHODS: A chart review of patients who had undergone LASIK between April 1999 and December 2001 was performed. Patients having known risk factors for epithelial ingrowth were excluded from the study. Both eyes of patients who were operated with both laser systems were included in a paired analysis. The first operated eyes of the remaining patients were included in an unpaired analysis. The outcomes studied were epithelial ingrowth (a region of epithelial growth under the flap that was contiguous with the flap edge and extended at least 0.7 mm in the radial direction) and epithelial ingrowth requiring treatment (extending into the pupillary zone, causing reduced vision, causing nighttime glare, or inducing any melting of the flap edge). RESULTS: In the paired study, 11 (61.1%) of 18 eyes treated with the VISX 20/20B had epithelial ingrowth, and 7 (38.9%) eyes required treatment. None of the eyes treated with the VISX Star S3 had epithelial ingrowth. In the unpaired study, 39 (37.1%) of 105 eyes treated with the VISX 20/20B were noted to have epithelial ingrowth and 14 (13.3%) eyes required treatment. None of the eyes treated with the VISX Star S3 had epithelial ingrowth. The incidence of epithelial ingrowth was significantly different for the VISX 20/20B and the VISX Star S3 in both analyses (paired: P<.001, McNemar's test; unpaired: P<.001, Fisher's exact test). CONCLUSIONS: The laser system used in LASIK is a risk factor for the development of epithelial ingrowth.
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