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Recovery of Corneal Subbasal Nerve Density After PRK and LASIK

2005; Elsevier BV; Volume: 140; Issue: 6 Linguagem: Inglês

10.1016/j.ajo.2005.07.027

1879-1891

Jay C. Erie, Jay W. McLaren, David O. Hodge, William M. Bourne,

Glaucoma and retinal disorders

Purpose To measure and compare the return of corneal innervation up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Design Prospective, nonrandomized clinical trial. Methods Eighteen eyes of 12 patients received PRK to correct a mean refractive error of –3.73 ± 1.30 diopters, and 16 eyes of 11 patients received LASIK to correct a mean refractive error of –6.56 ± 2.44 diopters. Corneas were examined by confocal microscopy before and at 1, 2, 3, and 5 years after the procedures. Subbasal nerve fiber bundles were measured to determine density (visible length of nerve/frame area) and expressed as micrometers per square millimeters. Differences were compared by Friedman’s test and adjusted for multiple comparisons by the Student-Newman-Keuls procedure. Results After PRK, mean subbasal nerve density was reduced by 59% at 1 year (2764 ± 1321 μm/mm2 [±SD]) when compared with preoperative (6786 ± 1948 μm/mm2; P < .001). By 2 years, subbasal nerve density (6242 ± 1763 μm/mm2) was not significantly different from density before PRK and remained unchanged to 5 years (5903 ± 3086 μm/mm2). After LASIK, subbasal nerve density was reduced by 51%, 35%, and 34% at 1, 2, and 3 years, respectively (P < .001). By 5 years, subbasal nerves had returned to densities (4441 ± 2819 μm/mm2) that were not significantly different from densities before LASIK (5589 ± 2436 μm/mm2). Conclusion Corneal subbasal nerve density does not recover to near preoperative densities until 5 years after LASIK, as compared with 2 years after PRK. To measure and compare the return of corneal innervation up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Prospective, nonrandomized clinical trial. Eighteen eyes of 12 patients received PRK to correct a mean refractive error of –3.73 ± 1.30 diopters, and 16 eyes of 11 patients received LASIK to correct a mean refractive error of –6.56 ± 2.44 diopters. Corneas were examined by confocal microscopy before and at 1, 2, 3, and 5 years after the procedures. Subbasal nerve fiber bundles were measured to determine density (visible length of nerve/frame area) and expressed as micrometers per square millimeters. Differences were compared by Friedman’s test and adjusted for multiple comparisons by the Student-Newman-Keuls procedure. After PRK, mean subbasal nerve density was reduced by 59% at 1 year (2764 ± 1321 μm/mm2 [±SD]) when compared with preoperative (6786 ± 1948 μm/mm2; P < .001). By 2 years, subbasal nerve density (6242 ± 1763 μm/mm2) was not significantly different from density before PRK and remained unchanged to 5 years (5903 ± 3086 μm/mm2). After LASIK, subbasal nerve density was reduced by 51%, 35%, and 34% at 1, 2, and 3 years, respectively (P < .001). By 5 years, subbasal nerves had returned to densities (4441 ± 2819 μm/mm2) that were not significantly different from densities before LASIK (5589 ± 2436 μm/mm2). Corneal subbasal nerve density does not recover to near preoperative densities until 5 years after LASIK, as compared with 2 years after PRK.