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[Retinal image quality pre- and post-lasik as a function of illuminance].

BACKGROUND
The aim of this study was to simulate the effect of illuminance on retinal image quality before and after LASIK.


PATIENTS AND METHODS
Wavefront sensing was performed in eighteen eyes of 12 patients before and one month after uncomplicated LASIK using a Hartmann-Shack sensor. A sigmoid curve was fitted to pupillometry data obtained at 4, 0.4 and 0.04 lux. Based on the sigmoid fit, pre- and postoperative wavefront errors were simulated for different pupil diameters over a corresponding range from 10 (-2) to 10 (2) lux. Retinal image quality was described by computation of the visual Strehl ratio based on the optical transfer function (VSOTF) for a spectacle correction preoperatively and for the uncorrected eye postoperatively.


RESULTS
At an illuminance of 1 lux the mean pupil diameter was 4.81 +/- 0.91 mm and log VSOTF dropped from -0.47 +/- 0.29 to -1.18 +/- 0.32 (p < 0.001) after LASIK. The steepest pupil-induced decrease of VSOTF occurred preoperatively at 0.67 +/- 0.26 lux (range 0.2 - 1.58 lux). After LASIK, L (crit) on average was 0.96 +/- 0.53 lux (p < 0.05; range 0.2 - 1.78).


CONCLUSIONS
The steepest pupil-induced decrease of retinal image quality occurred in the high mesopic range, however, there was intersubject variability.