Abstract
To assess efficacy, safety, predictability, stability, and changes in higher-order aberrations (HOAs) and contrast sensitivity (CS) after wavefront-guided and standard LASIK enhancement for the correction of residual refractive errors. Prospective, randomized, comparative clinical study. Twenty eyes of 20 consecutive patients (spherical equivalent [SE], -2.01+/-1.36 diopters [D]) treated with wavefront-guided Zyoptix Ablation Refinement software (ZAR) LASIK and 20 eyes of 20 consecutive patients (SE, -1.81+/-1.21 D) treated with standard Planoscan LASIK, both for residual refractive error enhancement. Efficacy, safety, predictability, stability, HOAs, and CS were evaluated before and after enhancement at 6 months' follow-up. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), manifest refraction, CS by means of the Functional Acuity Contrast Test, and HOAs by means of Zywave aberrometry were evaluated preoperatively and 6 months after retreatment. At 6 months postoperatively, UCVA was 20/25 or better in 100% of the eyes. Efficacy indexes were 1.09 for ZAR patients and 0.95 for Planoscan patients. No eyes lost > or =1 line of BCVA; in the ZAR group, 2 eyes gained 1 line and 6 eyes gained > or =2 lines; in the Planoscan group, 3 eyes gained 1 line. The ZAR group showed a percentage of eyes (94.4%) within the 0.5-D range in SE higher than that shown by the Planoscan group (88.8%). After 6 months, the HOA root mean square (RMS) increased on average by a factor of 1.44 for the Planoscan group (P = 0.003). No change or reduction in HOA RMS was found in the ZAR group (factor of 0.96; P>0.01). Contrast sensitivity was reduced in the Planoscan group only at the highest spatial frequency (18 cycles per degree; P<0.01). There was a significant reduction of CS as a function of HOA increase for the Planoscan group (P<0.0001). No changes were observed for the ZAR group at any spatial frequency (1.5-18 cycles per degree; P>0.01). Wavefront-guided LASIK using the ZAR algorithm is an effective and safe procedure for treatment of residual refractive errors. Wavefront-guided LASIK does not increase HOAs and does not modify CS compared with preoperative values. Wavefront-guided LASIK seems to be better than standard LASIK for retreatments.
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