Change in epithelial thickness profile 24 hours and longitudinally for 1 year after myopic LASIK: three-dimensional display with Artemis very high-frequency digital ultrasound.

PURPOSE

To longitudinally follow epithelial thickness profile changes after myopic LASIK for 1 year to determine when and how epithelial changes occur and when epithelial stability is reached.

METHODS

Epithelial thickness was measured with Artemis very high-frequency digital ultrasound (ArcScan Inc) across the central 10-mm corneal diameter in 11 eyes before and 1 day, and 1, 3, 6, and 12 months after myopic femtosecond LASIK. For each consecutive pair of time points, maps of the mean change in epithelial thickness and paired t test P value were plotted.

RESULTS

Mean preoperative spherical equivalent refraction was -3.34 ± 1.51 diopters (D) (range: -1.50 to -5.13 D). Overnight, there was a central 5-mm zone of epithelial thickening (0.5 to 1.5 μm, P<.05) surrounded by epithelial thinning (4 to 6 μm, P<.05) extending to the 8-mm zone. Between 1 day and 1 month, the epithelium thickened within the 7-mm zone by up to 5 μm (P<.05) in a lenticular pattern with greater thickening centrally and progressively less thickening centrifugally. Between 1 and 3 months, the epithelium continued to thicken in the central 7-mm zone by approximately 1 μm (P<.05). No change in epithelial thickness occurred after 3 months (P>.05).

CONCLUSIONS

A lenticular change occurred in the epithelial thickness profile, with more thickening centrally than paracentrally; 22% of the total increase in central thickness occurred overnight, 58% between 1 day and 1 month, and 20% between 1 and 3 months, with stability between 3 and 12 months. The lenticular epithelial changes contribute to the observed myopic shift after myopic LASIK during the first 3 months.