Abstract Objective To evaluate the differences in contrast visual acuity (VA) under different background illuminations in patients who had been implanted with the ReSTOR aspheric multifocal intraocular lens (MIOL)(SN6AD3). Methods This was a prospective study. Forty-two eyes of 26 patients who had received ReSTOR MIOL (SN6AD3) implantation after cataract extraction were enrolled. Six months postoperatively, best corrected distance VA was measured at 4 contrast levels (100%, 25%, 10%, 5%) under 3 background illumination levels (250 cd/m2, 85 cd/m2, 25 cd/m2)using a multi-functional visual acuity tester (MFVA-100). Dunnett's T3 multiple comparison was used for statistical anaylysis. Results The mean VA at the 4 contrast levels (100%, 25%, 10%, 5%)under 250 cd/m2 background illumination were 0.01, 0.23, 0.40 and 0.62; under 85 cd/m2, the mean VA were 0.02, 0.26, 0.46 and 0.74; under 25 cd/m2, the mean VA were 0.08, 0.32, 0.49 and 0.63. At the same background illumination level, there was a statistically significant decrease in VA with a decrease in contrast level (P<0.05). While at the same contrast level, there were no statistically significant differences in VA at different background illuminations (250 cd/m2, 85 cd/m2,25 cd/m2)(P>0.05). Conclusion Implantation of the ReSTOR MIOL (SN6AD3) offers excellent VA under high luminance (250 cd/m2), normal luminance (85 cd/m2) and moderate luminance (25 cd/m2).VA is affected much more by the contrast of the visual target rather than background illumination.
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