Testing the dioptric power accuracy of exact-power-labeled intraocular lenses

PURPOSE: To test the accuracy of exact-power-labeled intraocular lenses (IOLs) in a limited independent study. SETTING: U.S. Food and Drug Administration Optical Testing Lab. METHODS: Hydrophilic acrylic IOLs were measured using a new confocal laser method for dioptric power measurement per International Organization for Standards standard 11979-2 and American National Standards Institute standard Z80.7. Some of the IOLs were measured at 22 degrees C and 35 degrees C. RESULTS: For the 18 IOLs tested, the mean difference between the manufacturer's exact labeled power (D(EL)) and the power measured in the study (D(M)) was 0.18 diopter (D) +/- 0.12 (SD) and between D(M) and the usual normal rounded-off (0.50 D steps) dioptric power (D(UL)) labeling, 0.23 +/- 0.09 D (difference 0.05 D). For 15.00 to 20.0 D IOLs, the mean difference between D(M) and D(EL) was 0.08 +/- 0.05 D and between D(M) and D(UL), 0.17 +/- 0.06 D (difference 0.09 D). For IOLs of 20.00 D or greater, the mean difference between D(M) and D(EL) was 0.24 +/- 0.11 D and between D(M) and D(UL), 0.27 D +/- 0.08 D (difference 0.03 D). When the IOL hydration temperature increased from 22 degrees C to 35 degrees C (4 IOLs tested), the IOL power increase on average was approximately 0.13 D. CONCLUSIONS: The small improvement in power-prediction accuracy for exact-power-labeled IOLs decreased in IOLs of 20.00 D or greater. For IOLs of 15.00 to 20.00 D, the increased accuracy (+/-0.09 D) was statistically significant and could increase predictability of postoperative refractions. Acrylic dioptric power was directly proportional to temperature.