Comparison of Three Formulas for Intraocular Lens Power Formula Accuracy

PURPOSE: To compare the accuracy of three intraocular lens (IOL) power calculation formulas (SRK/T, Barrett Universal II, and T2) in cataract surgery patients.METHODS: In total, 73 eyes of 73 patients who underwent uneventful cataract surgery were retrospectively reviewed. IOL power was determined using SRK/T, Barrett Universal II, and T2 preoperatively. The findings were compared with the actual refractive outcome to obtain the prediction error. The mean prediction error (ME) and mean absolute error (MAE) of each formula were compared. The MAE was defined as the difference between the postoperative spherical equivalence (SE) and the preoperatively predicted SE. The ME and MAE of each formula 3 months after surgery were compared with preoperatively predicted SE. Eyes were classified into subgroups based on axial length (AL) and average keratometry (K).RESULTS: The ME and MAE for the three formulas were SRK/T [−0.08 ± 0.45 diopters (D) and 0.35 ± 0.40 D, respectively], Barrett Universal II (−0.01 ± 0.44 D and 0.33 ± 0.30 D, respectively), and T2 (0.04 ± 0.45 D and −0.34 ± 0.30 D, respectively), but no statistically significant differences were detected. Similar results were obtained in groups with a long AL or a large average K. In groups with an AL ≥ 26 mm or with an average K ≥ 47 D, the Barrett Universal II formula yielded the smallest standard deviation and a ME closest to zero, but these differences were not statistically significant.CONCLUSIONS: No significant differences were observed between the three formulas regarding ME or MAE. However, recent formulas such as the Barrett Universal II could provide certain benefits in predicting IOL power for patients with a long AL (> 26 mm) or larger average K. Further research with a larger sample size is recommended for more evaluation.

Accuracy of the refractive prediction determined by intraocular lens power calculation formulas in high myopia

Purpose: Our study was conducted to evaluate and compare the accuracy of the refractive prediction determined by the calculation formulas for different intraocular lens (IOL) powers for high myopia. Methods: This study reviewed 217 eyes from 135 patients who had received cataract aspiration treatment and IOL implantation. The refractive mean numerical error (MNE) and mean absolute error (MAE) of the IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) were examined and compared. The MNE and MAE at different axial lengths (AL) were compared, and the percentage of every refractive error absolute value for each formula was calculated at ±0.25D, ±0.50D, ±1.00D, and ±2.00D. Results: In all, 98 patients were recruited into this study and 98 eyes of them were analyzed. We found that Barrett Universal II formula had the lowest MNE and MAE, SRK/T and Haigis formulas arrived at similar MNE and MAE, and the MNE and MAE calculated by Holladay and Hoffer Q formula were the highest. Barrett Universal II formulas have the lowest MAE among different AL patients, whereas it reached the highest percentage of refractive error absolute value within 0.5D in this study. The MAE of each formula is positively correlated with AL. Conclusion: Barrett Universal II formula rendered the lowest predictive error compared with SRK/T, Haigis, Holladay, and Hoffer Q formulas. Thus, Barrett Universal II formula may be regarded as a more reliable formula for high myopia.