Methods for Intraocular Lens Power Calculation in Cataract Surgery after Radial Keratotomy

Area of Science:

• Ophthalmology
• Refractive Surgery
• Biomedical Engineering

Background:

• Radial keratotomy (RK) alters corneal curvature, complicating intraocular lens (IOL) power calculations for subsequent cataract surgery.
• Accurate IOL power is crucial for achieving desired refractive outcomes post-cataract extraction.

Purpose of the Study:

• To compare the accuracy of various IOL calculation formulas in eyes previously treated with RK.
• To evaluate the impact of refractive history on IOL power calculation accuracy after RK.

Main Methods:

• Retrospective analysis of 52 eyes from 34 patients who underwent sequential RK and cataract surgery.
• Evaluation of seven IOL calculation formulas, including different versions of the True K formula.
• Comparison of achieved spherical equivalent outcomes with target outcomes to determine absolute error.

Main Results:

• The True K formula utilizing refractive history yielded the best results (lowest median absolute error).
• Formulas without refractive history, such as True K [No History] and Haigis, demonstrated comparable accuracy.
• Double-K Holladay 1 and Potvin-Hill formulas were found to be least accurate.

Conclusions:

• Refractive history significantly enhances IOL power calculation accuracy in post-RK patients.
• The True K formula with historical data offers superior precision for IOL power calculation.
• When refractive history is unavailable, True K [No History] and Haigis formulas are reliable alternatives.