Epithelial Hyperplasia in PRK Enhancements Over LASIK
Purpose
Unexpected over corrections after PRK enhancements for regression after myopic LASIK are not uncommon. Epithelial hyperplasia has been postulated as a contributing cause of these over corrections. This study explores epithelial thickness before PRK enhancements over LASIK in an effort to determine if there is a correlation with over corrections.
Methods
Epithelial thickness was measured in 21 eyes of 17 patients before PRK enhancement over myopic LASIK. Refractive effect compared to expected result was correlated to starting epithelial thickness. Variance from expected refractive result in all eyes was measured at one, three and six months by masked observers and compared to initial epithelial thickness.
Results
There was a clinically significant correlation between starting epithelial thickness and variance from expected refractive outcome. Patients with thicker initial epithelial thicknesses were more likely to experience over corrections. The degree of over correction was positively correlated to starting epithelial thickness.
Conclusion
Epithelial hyperplasia was shown in this study to be a factor in over corrections in PRK enhancements over myopic LASIK. Measuring epithelial thickness before PRK enhancement can be useful in improving the accuracy of PRK enhancements.