Significant postoperative refractive errors in vivo with the Mentor Memorylens intraocular lens.

PURPOSE

To determine the difference between the predicted and postoperative refraction in eyes after implantation of the Mentor MemoryLens intraocular lens (IOL) and compare these results with those of 2 other types of foldable IOLs implanted by the same surgeons.

SETTING

Community-based group practice ophthalmology clinic.

METHODS

All operated eyes (341) of all patients who had routine phacoemulsification with implantation of a MemoryLens IOL performed by 1 of 2 surgeons were evaluated retrospectively. The predicted refractive error and actual postoperative refractive error were compared in each eye in the MemoryLens group and in 2 smaller control groups with an AcrySof acrylic (Alcon) or SI-40 silicone (Allergan Medical Optics) IOL implanted by the same surgeons using identical technique and IOL calculation parameters. Patients in whom the difference between the predicted and actual postoperative refraction fell significantly outside expected parameters were rechecked with repeat axial length and keratometric readings, and these measurements were used to back-calculate the effective in vivo IOL power.

RESULTS

The MemoryLens group had significantly greater variability in postoperative refractive results from those predicted by the Hoffer program than the 2 control groups. The postoperative refractive error in the MemoryLens group differed from +1.50 to -5.50 diopters (D) from that predicted by the IOL calculation formulas. When the outlier groups (ie, greater than +0.50 D or less than -1.00 D from predicted refractive error) were evaluated and compared to the rest of the MemoryLens group and the 2 control groups, no significant difference in axial length, keratometric measurements, operative surgeon, surgical technique, or patient age was found. Repeat axial length and keratometric measurements in the outlier group were not significantly different from those in the same eyes preoperatively. Back-calculation using postoperative axial length and keratometric measurements in the highly myopic outlier group showed that the mean difference between the labeled IOL power and actual in vivo IOL power in the outlier group was -3.08 D (range -1.98 to -7.54 D). The best corrected visual acuity was not affected in patients in the outlier groups despite the refractive variability.

CONCLUSION

The variation in postoperative refractive results in the MemoryLens group was significantly greater than in the 2 other foldable IOL groups.