Comparison of tolerance to induced astigmatism in pseudophakic eyes implanted with small aperture, trifocal, or monofocal intraocular lenses
Robert Edward Ang
Department of Cornea and Refractive Surgery, Asian Eye Institute, Makati City, Philippines
Purpose: To compare the effect of induced astigmatic defocus on visual performance in pseudophakic eyes implanted with a small aperture, trifocal, or monofocal intraocular lens (IOL).
Patients and methods: The study included 44 eyes with one of four types of IOL (IC-8 IOL (AcuFocus Inc., USA); FineVision (PhysIOL SA, Belgium); AT Lisa (Carl Zeiss AG, Germany); and enVista monofocal (Bausch & Lomb, USA). For astigmatic tolerance assessment, monocular distance visual acuity was measured with cylindrical lenses (power range=0.00–2.50 diopters (D) in 0.50 D increments) added to the subjects best-corrected distance manifest refraction. The assessment was repeated on three pre-determined axes (90°, 180°, and either 45° or 135°). The magnitude of astigmatic tolerance at each defocus step was assessed by taking the difference between logMAR visual acuity at the defocus step relative to that at 0.0 D (ie, no defocus condition).
Results: Across all three axes, the reduction of mean monocular visual acuity at all defocus levels relative to no defocus was significantly smaller in IC-8 group compared to the other IOL groups. When the data was combined across all axes, the astigmatic tolerance of the IC-8 group was better than AT Lisa group from 0.50 D to 2.50 D and FineVision group from 0.50 D to 1.50 D (all P<0.05, ANOVA). The IC-8 group was better than the enVista group, but not significantly (P>0.05, ANOVA). Among individual orientations, statistically significant differences were seen between IC-8 IOLs and the other IOLs, with the largest difference being in the oblique axis. Astigmatic tolerance at all axes combined was 1.40 D for IC-8 IOL, 0.70 D for AT Lisa and FineVision, and 1.00 D for enVista IOLs.
Conclusion: The small aperture IC-8 IOL showed greater tolerance to induced astigmatic defocus compared to trifocal and monofocal IOLs.
Keywords: cataract, refractive error, small aperture IOL, residual astigmatism
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