Refractive tolerance in the use of monofocal intraocular lenses enhanced with new aspheric design.

Purpose: To evaluate the refractive tolerance in eyes with enhanced monocular intraocular lens (IOL) with a new aspheric design.

Methods: This study included two assessments. Clinical records of consecutive eyes with conventional monofocal IOL (SY60WF, Alcon) were retrospectively reviewed, and changes in uncorrected distance visual acuity (UDVA) with myopic and hyperopic refractive errors were evaluated using segmented regression analysis. Next, in 39 eyes of 39 cataract patients who received an enhanced monofocal IOL (NSP-3, Nidek), UDVA, refractive error, and photopic and mesopic contrast sensitivities were examined at one-three months postoperatively. Changes in the UDVA with refractive error were evaluated in the same manner. With resultant segmented regression lines, ranges of UDVA of 0.20 logMAR or better were obtained as refractive tolerances.

Results: The clinical records of 717 eyes of 551 patients with SY60WF were analyzed. Segmented regression analysis revealed a breakpoint in emmetropia and UDVA degradation myopically and hyperopically. The refractive tolerance was 2.03 D, while it was 0.73 D on the myopic side. In the prospective study, there was a breakpoint at -1.088 D, where there was a relatively flat slope between the breakpoint and emmetropia, then UDVA steeply degraded. Refractive tolerance on the myopic side was 1.12 D. There was no significant degradation in the photopic/mesopic contrast sensitivity.

Conclusion: Enhanced monofocal IOLs provided wider myopic refractive tolerance, in which UDVA of 0.2 logMAR or better would be anticipated between emmetropia and myopic error of -1.12 D.