A No History Multi-Formula Approach To Improve The Iol Power Calculation After Laser Refractive Surgery

To propose a multi-formula approach by comparing no-history intraocular lens (IOL) power calculation methods after myopic laser-refractive-surgery (LRS).

University Eye Clinic, Department of Medicine and Surgery, University of Salerno, Italy.

In this retrospective, comparative study, one-hundred-thirty-two eyes of 132 patients who had myopic LRS and subsequent cataract surgery were examined. ALMA, Barrett True-K, Ferrara, Jin, Kim, Latkany and Shammas methods were evaluated, as appropriate to back-calculate the refractive Prediction Error (PE) with the implanted IOL. To eliminate the lens-factor bias, the mean error (ME) was zeroed-out for each formula. Median absolute error (MedAE) and percentage of eyes within ±0.50 and ±1.00 diopters (D) of PE were analyzed. PE were plotted with the corresponding mean keratometry (K), axial length (AL) and AL/K ratio and then different ranges were evaluated.

Zeroing-out the ME (90 eyes), when K≤38.00D with AL>28.00mm and when 38.00D<K≤40.00D  with 26.50mm<AL≤29.50mm ALMA gave the best results; when K≤38.00D with AL≤26.50mm and when K>40.00D with AL≤28.00mm or AL>29.50mm Barrett True-K was the best; in other ranges, both ALMA and Barrett True-K were the best. (P<0.05) Without zeroing-out the ME (132 eyes), when K>38.00D with AL≤29.50mm and when 36.00<K≤38.00D with AL≤26.50mm ALMA was the best;  when K≤36.00D and when K≤38.00D with AL>29.50mm Barrett True-K was the best; in other ranges, both ALMA and Barrett True-K were the best. (P<0.05)

A multi-formula approach according to different ranges of K and AL could improve refractive outcomes in post LRS eyes.