Contrast sensitivity after implantation of a spherical versus an aspherical intraocular lens in biaxial microincision cataract surgery

PURPOSE: To determine whether implantation of a microincision intraocular lens (IOL) with a modified anterior surface, designed to compensate for the positive spherical aberration of the cornea in eyes of cataract patients, results in improved pseudophakic quality of vision in pseudophakic eyes after biaxial microincision phacoemulsification. SETTING: Department of Ophthalmology, Johannes Gutenberg-University, Mainz, Germany. METHODS: In a nonrandomized parallel cohort investigation, the visual performance of 52 eyes of 52 patients unilaterally implanted with the aspherical Acri.Smart 36 A IOL (Acri.Tec) were compared with those of 25 eyes of 25 age-matched patients unilaterally implanted with the spherical Acri.Smart 46 S IOL (Acri.Tec). Eight weeks after surgery, the following parameters were assessed: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), pupil size under various illumination conditions, high-contrast and low-contrast visual acuities, photopic and mesopic contrast sensitivities, capsulorhexis size, and wavefront aberration of the cornea and eye. The primary clinical endpoint of the comparison was defined as the area under the cycles per degree (cpd) curve of the contrast sensitivity profile. RESULTS: The aspherical IOL group and the spherical IOL group did not differ in baseline characteristics. The median age was 71 years and 68% were women in the aspherical group versus 69 years and 62% women in the spherical group. The preoperative median UCVA was 20/80 in both groups. The UCVA, BCVA, pupil size, and capsulorhexis size were not statistically different between the 2 groups. Furthermore, no clinically relevant or statistically significant between-group differences were observed in the primary clinical endpoint. The median postoperative low mesopic contrast sensitivity without glare was 73 cpd in the aspherical group and 84 cpd in the spherical group (P =.624); a similar tendency was observed under high mesopic conditions (median 80 cpd and 83 cpd, respectively) (P = 1.000). Implantation of both IOL types resulted in a negative spherical aberration Z(4)(0), which was significantly different between the 2 groups (median -0.09 mu m aspherical and -0.29 mu m aspherical at a pupil size of 4.5 mm) (P<.001). CONCLUSIONS: No clinically relevant postoperative differences in contrast sensitivity were observed between the aspherical microincision IOL and the spherical equivalent model. The development of microincision IOLs, which fit through corneal incisions smaller than 2.0 mm and improve night-driving conditions (eg, reduction of glare), could optimize modern biaxial cataract surgery.