Accuracy of Traditional and Modern Formulas for Intraocular Lens Power Calculation After Radial Keratotomy Using Standard Keratometry

Abstract

Purpose

To compare the accuracy of multiple traditional and modern intraocular lens (IOL) power calculation formulas in post-radial keratotomy (RK) patients undergoing cataract surgery.

Methods

This retrospective case series included 50 eyes with prior RK who underwent routine phacoemulsification surgery with single-piece acrylic IOL implantation (A constant = 118.8). Outcomes of multiple formulas were calculated. Included formulas were SRK/T, Holladay 1, Holladay 2, Haigis, Barrett True-K, Haigis and Barrett True-K (target refraction of 0.50 D), Barrett Universal II, Kane, PEARL-DGS, Shammas no history, DK SRK/T, DK SRK/T (target refraction of 0.50 D), Double K (DK) Holladay 1, and DK Holladay 1 (target refraction of 0.50 D). Averages of multiple combinations of best-performing single formulas were calculated. Primary outcome is mean absolute error (MAE).

Results

Haigis (with −0.50 D target refraction) and DK SRK/T showed the lowest mean and median absolute errors (MedAE) followed by Haigis, Barrett True-K, and Barrett True-K (with −0.50 D target refraction). Combinations of 3, 4, or 5 of best performing single formulas yielded good results with >60% of cases within +0.50 D of intended refraction and MAE around 0.50 D. The best performing formulas with flatter K readings were PEARL-DGS and Haigis (with additional −0.50 D target refraction) with MAE of 0.72 + 0.71 D and 0.70 + 0.70 D, respectively, followed by Barrett True-K (with intended −0.50 D target refraction) with MAE of 0.75 + 0.63 D.

Conclusion

Using an average of three or more Haigis (with −0.50 D target refraction), the Barrett True-K, DK Holladay 1, and DK SRK/T formulas showed better outcomes than using a single formula for IOLMaster 700 standard K readings. The PEARL-DGS formula showed better accuracy in eyes with flatter K readings (<38 D).

Keywords:

• radial keratotomy
• IOL calculation
• PEARL-DGS
• Barrett True-K
• DK Holladay 1
• DK SRK/T

Abbreviations

RK, radial keratotomy; IOL, intraocular lens; K, keratometry; ELP, effective lens position; AL, axial length; SER, second eye refinement; MRSE, manifest refraction spherical equivalent; DK, double K; MAE, mean absolute error; MedAE, median absolute error.

Data Sharing Statement

Available upon request from the authors.

Ethics and Consent to Participate

This study was approved by the local ethics committee of the Faculty of Medicine, Alexandria University, Egypt. The tenets of the Declaration of Helsinki were followed for this study. All the included patients were recalled for the final follow-up visit and signed an informed consent form.

Author Contributions

Dr. Hany Ahmed Helaly: the idea and concept of the study, shared in writing the manuscript, and collecting and analyzing data. Dr. Amr Mohamed Elhady: shared the idea of the study, wrote the manuscript, and analyzed the data. Dr. Osama Ramadan Elnaggar: shared in writing and revising the manuscript, data analysis, and the idea of the study. “All authors contributed to data analysis, drafting or revising the article, agreed on the journal to which the article was submitted, agreed on all the versions of the article before submission and during revision, gave final approval of the accepted version to be published and any significant changes introduced at the proofing stage, and agreed to be accountable for all aspects of the work”.

Disclosure

The authors report no conflicts of interest in this work.

Additional information

Funding

There is no funding to report.