Contrast sensitivity function in eyes with diffractive bifocal intraocular lenses

PURPOSE: To evaluate the image quality of asymmetric Acri.Twin bifocal intraocular lenses (IOLs) (Acri.Tec) by comparing distance and near black-white contrast sensitivity function with that of the Pharmacia 811E IOL. SETTING: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. METHODS: Thirty-two eyes of 16 patients were examined after contralateral implantation of 1 Acri.Twin near-weighted 733D IOL and 1 Acri.Twin distance-weighted 737D IOL. Twenty eyes in 10 patients were examined after binocular Pharmacia 811E IOL implantation. Best corrected distance and near visual acuities were determined. Individual reading distance was recorded and corrected to 40 cm for the near contrast test (Holladay Contrast Acuity Test). Distance contrast sensitivity function was evaluated using the Acuity Max (Science 2020) computer program. RESULTS: Best corrected distance visual acuity was significantly better in patients with the 737D IOL than in those with the 733D or 811E IOLs. For distance reading with best distance correction, the 733D IOL performed better than the 737D and the 811E. Individual reading distance with the Acri.Twin IOL and 811E IOL was 33.6 cm and 34.0 cm, respectively. Best distance-corrected near contrast sensitivity function was better in eyes with the near-weighted 733D IOL. Binocular testing showed a significant difference between the 2 groups only at low-contrast values. At distance, contrast sensitivity function was better with the 737D IOL, whereas no difference was found between the 733D and the 811E IOLs. Binocular contrast sensitivity function at distance revealed statistically significantly better results in the Acri.Twin group. CONCLUSION: An asymmetric diffractive bifocal lens system was advantageous in terms of vision quality when implanted binocularly and superior to monocular stronger weighted focus compared with conventional bifocal IOLs.