Purpose: To compare the effects on contrast sensitivity of the IntraLase femtosecond laser for flap creation (IntraLASIK) and standard LASIK for myopia.
Methods: Two hundred eyes of 100 consecutive patients underwent LASIK treatment using the VISX S2 laser system. The femtosecond laser (15 kHz IntraLase) was used for flap creation in 100 eyes (50 patients) and a mechanical microkeratome (Carriazo-Barraquer) was used in 100 eyes (50 patients). Best spectacle-corrected contrast sensitivity was measured before and 6 months postoperatively in the IntraLASIK and mechanical LASIK groups. The IntraLASIK and mechanical LASIK-induced changes in contrast sensitivity were compared under photopic (85 cd/m2) and mesopic (5, 2.5, and 0.1 cd/m2) conditions.
Results: Contrast sensitivity for eyes after IntraLASIK did not differ from preoperative values at the photopic level (85 cd/m2). However, under mesopic conditions, a statistically significant reduction (P < .01) in contrast sensitivity was found at high spatial frequencies (12 and 18 cpd), although no significant contrast sensitivity differences were observed at low and middle spatial frequencies (P > .01 for 1.5, 3, and 6 cpd). No statistically significant differences were found between IntraLASIK and mechanical LASIK for 1.5, 3, and 6 cpd at any luminance level (P > .01). IntraLASIK showed better contrast sensitivity than mechanical LASIK under mesopic conditions at 12 cpd and photopic and mesopic conditions at 18 cpd (P < .01).
Conclusions: IntraLASIK surgery demonstrated better contrast sensitivity at high spatial frequencies under photopic and mesopic conditions than mechanical LASIK.