Natural History and Incidence of Rainbow Glare and Light Scattering in Femtosecond LASIK
To assess the incidence and long-term outcomes of rainbow glare and light-scattering in femtosecond laser-assisted in situ keratomileusis.
Fifty myopic eyes underwent LASIK using the ALLEGRETTO Eye-Q excimer laser with refraction ranging from -1.00 to -7.25 diopters (mean -3.31±1.9). Flap creation was randomized between eyes, using the IntraLASE FS60 (IL) in one eye and WaveLight FS200 (FS) in the contralateral eye. Rainbow glare (radiating colors around a white ophthalmic light source under mesopic and scotopic conditions) and light scattering test (C-Quant, Oculus Inc) were obtained preoperatively and at 1 week, 1, 3 and 9 months postoperatively. Manifest and wavefront refractions were performed at each postoperative visit.
Light-scattering peaked at 1 week postoperatively in both IL and FS groups (log 1.28±0.16, p=0.02 and log 1.26±0.12, p=0.039, respectively) with statistically significant improvement at 3 months (log 1.11±0.35, p=0.007 and log 1.19±0.14, p=0.04) and 9 months (log 1.10±0.16, p=0.008 and log 1.14±0.13, p=0.011). 11 patients reported postoperative rainbow glare at 1 week, 9 at 1 month, 5 at 3 months and 6 at 9 months in the IL group and 14 patients at 1 week , 11 at 1 month, 5 at 3 months and 6 at 9 months in the FS group. No statistically significant differences were found between IL and FS groups at all time points. Rainbow glare and light scattering did not correlate with refractive error, age, or gender.
The time course of rainbow glare and light scattering were quantified; both optical side effects were greatest at 1 week and significantly decreased between 1 month and 9 months postoperatively. Optical side-effects of femtosecond laser did not correlate with postoperative clinical outcomes. Rainbow glare and light scattering are mild optical side effects of femtosecond LASIK that gradually improve with time.