Comparison of intraocular lens power prediction accuracy of formulas in American Society of Cataract and Refractive Surgery post-refractive surgery calculator in eyes with prior radial keratotomy

Purpose

To evaluate the accuracy of intraocular lens (IOL) power prediction of the formulas available on the American Society of Cataract and Refractive Surgery (ASCRS) post-refractive calculator in eyes with prior radial keratotomy (RK) for myopia.

Methods

This retrospective study included 25 eyes of 18 patients whose status was post-RK for treatment of myopia, which had undergone cataract extraction with IOL implantation. Prediction error was calculated as the difference between implanted IOL power and predicted power by various formulae available on ASCRS post-refractive calculator. The formulas compared were Humphrey Atlas method, IOLMaster/Lenstar method, Barrett True-K no-history formula, ASCRS Average power, and ASCRS Maximum power on ASCRS post-refractive calculator.

Results

Median absolute errors were the least for Barrett True-K and ASCRS Maximum power, that is, 0.56 (0.25, 1.04) and 0.56 (0.25, 1.06) D, respectively, and that of Atlas method was 1.60 (0.85, 2.28) D. Median arithmetic errors were positive for Atlas, Barrett True-K, ASCRS Average (0.86 [-0.17, 1.61], 0.14 [-0.22 to 0.54], and 0.23 [-0.054, 0.76] D, respectively) and negative for IOLMaster/Lenstar method and ASCRS Maximum power (-0.02 [-0.46 to 0.38] and - 0.48 [-1.06 to - 0.22] D, respectively). Multiple comparison analysis of Friedman's test revealed that Atlas formula was significantly different from IOLMaster/Lenstar, Barrett True-K, and ASCRS Maximum power; ASCRS Maximum power was significantly different from all others (P < 0.00001).

Conclusion

In post-RK eyes, Barrett True-K no-history formula and ASCRS Maximum power given by the ASCRS calculator were more accurate than other available formulas, with ASCRS Maximum leading to more myopic outcomes when compared to others.

A comparison of the American Society of Cataract and Refractive Surgery post-myopic LASI K/PRK intraocular lens (IOL) calculator and the Ocular MD IOL calculator

Background

To compare the average values of the American Society of Cataract and Refractive Surgery (ASCRS) and Ocular MD intraocular lens (IOL) calculators to assess their accuracy in predicting IOL power in patients with prior laser-in-situ keratomileusis (LASIK) or photorefractive keratectomy.

Methods

In this retrospective study, data from 21 eyes with previous LASIK or photorefractive keratectomy for myopia and subsequent cataract surgery was used in an IOL calculator comparison. The predicted IOL powers of the Ocular MD SRK/T, Ocular MD Haigis, and ASCRS averages were compared. The Ocular MD average (composed of an average of Ocular MD SRK/T and Ocular MD Haigis) and the all calculator average (composed of an average of Ocular MD SRK/T, Ocular MD Haigis, and ASCRS) were also compared. Primary outcome measures were mean arithmetic and absolute IOL prediction error, variance in mean arithmetic IOL prediction error, and the percentage of eyes within ±0.50 and ±1.00 D.

Results

The Ocular MD SRK/T and Ocular MD Haigis averages produced mean arithmetic IOL prediction errors of 0.57 and −0.61 diopters (D), respectively, which were significantly larger than errors from the ASCRS, Ocular MD, and all calculator averages (0.11, −0.02, and 0.02 D, respectively, all P < 0.05). There was no statistically significant difference between the methods in absolute IOL prediction error, variance, or the percentage of eyes with outcomes within ±0.50 and ±1.00 D.

Conclusion

The ASCRS average was more accurate in predicting IOL power than the Ocular MD SRK/T and Ocular MD Haigis averages alone. Our methods using combinations of these averages which, when compared with the individual averages, showed a trend of decreased mean arithmetic IOL prediction error, mean absolute upper limit of IOL prediction error, and variance, while increasing the percentage of outcomes within ±0.50 D.

Evaluation of the American Society of Cataract and Refractive Surgery intraocular lens calculator for eyes with prior radial keratotomy

BACKGROUND

The purpose of this study was to evaluate the American Society of Cataract and Refractive Surgery (ASCRS) intraocular lens (IOL) calculator for eyes with prior radial keratotomy and assess the accuracy of its methods in predicting IOL power in patients with previous radial keratotomy.

METHODS

This retrospective study included data from 15 eyes with previous radial keratotomy and subsequent cataract surgery. The average central power and Humphrey Atlas methods from the ASCRS IOL calculator, along with an average IOL power produced from an average of these two methods (ASCRS average), were compared. Primary outcome measures for each method were mean arithmetic and absolute IOL prediction error, variance in mean arithmetic IOL prediction error, and the percentage of refractive outcomes within ±0.50, ±1.00, ±1.50, and ±2.00 diopters (D).

RESULTS

The average central power method and the ASCRS average were significantly more accurate than the Humphrey Atlas method in terms of mean absolute IOL prediction error (1.03 D and 1.02 D versus 1.53; P = 0.04 and P = 0.01, respectively). In addition, the average central power method and ASCRS average produced a higher percentage of refractive outcomes within ±0.50 D when compared with the Humphrey Atlas method (60% and 46.67% versus 0%, respectively). A comparison of the average central power method and the ASCRS average demonstrated a smaller variance and higher percentage of patients within ±1.00 D when using the ASCRS average.

CONCLUSION

The ASCRS calculator for eyes with prior radial keratotomy is an easily accessible and valuable online tool for calculating IOL power in patients with previous radial keratotomy. We found that the ASCRS average produced by the calculator provided the best IOL prediction. We recommend using it with the addition of 1.00 to 1.50 D to its IOL power prediction.