Flap thickness in eyes with ectasia after laser in situ keratomileusis.

PURPOSE: To measure central flap thickness in eyes with ectasia after laser in situ keratomileusis (LASIK) and to compare these values with estimated anticipated flap thickness based on mean published values for each device used for flap creation.
SETTING: Emory Vision at Emory University, Atlanta, Georgia, USA.
DESIGN: Retrospective comparative case series, using published data for controls.
METHODS: Confocal microscopic analysis was performed using the Confoscan 3 device to measure central flap thickness in eyes with ectasia after LASIK. Pre-LASIK records were evaluated for information, including basic patient demographics, preoperative corneal topographies, estimated anticipated flap thickness based on the mean average thickness values, and residual stromal bed (RSB) thickness calculations using measured and estimated flap thicknesses.
RESULTS: Fifty eyes of 29 patients were evaluated. The mean measured flap thickness was 138 μm ± 26 (SD) (range 90 to 220 μm). There were no significant differences between measured and estimated flap thicknesses (138 μm versus 135 μm; P=.5) or RSB thickness (329 μm versus 332 μm; P=.7), nor were there differences in flap thickness between eyes developing ectasia with normal corneal topographies and eyes with abnormal corneal topographies. One eye had a measured flap resulting in an unintended RSB thickness less than 250 μm; this eye also had abnormal topography.
CONCLUSIONS: Measured central flap thickness was not thicker than estimated in most eyes developing ectasia after LASIK. Thus, excessively thick flaps do not appear to be a major contributing factor to the pathogenesis of ectasia after LASIK. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.