A No-History Multi-Formula Approach to Improve the IOL Power Calculation after Laser Refractive Surgery: Preliminary Results

Abstract

This retrospective comparative study proposes a multi-formula approach by comparing no-history IOL power calculation methods after myopic laser-refractive-surgery (LRS). One-hundred-thirty-two eyes of 132 patients who had myopic-LRS and cataract surgery were examined. ALMA, Barrett True-K (TK), Ferrara, Jin, Kim, Latkany and Shammas methods were evaluated in order to back-calculate refractive prediction error (PE). To eliminate any systematic error, constant optimization through zeroing-out the mean error (ME) was performed for each formula. Median absolute error (MedAE) and percentage of eyes within ±0.50 and ±1.00 diopters (D) of PE were analyzed. PEs were plotted with corresponding mean keratometry (K), axial length (AL), and AL/K ratio; then, different ranges were evaluated. With optimized constants through zeroing-out ME (90 eyes), ALMA was better when K ≤ 38.00 D-AL > 28.00 mm and when 38.00 D < K ≤ 40.00 D-26.50 mm < AL ≤ 29.50 mm; Barrett-TK was better when K ≤ 38.00 D-AL ≤ 26.50 mm and when K > 40.00 D-AL ≤ 28.00 mm or AL > 29.50 mm; and both ALMA and Barrett-TK were better in other ranges. (p < 0.05) Without modified constants (132 eyes), ALMA was better when K > 38.00 D-AL ≤ 29.50 mm and when 36.00 < K ≤ 38.00 D-AL ≤ 26.50 mm; Barrett-TK was better when K ≤ 36.00 D and when K ≤ 38.00 D with AL > 29.50 mm; and both ALMA and Barrett-TK were better in other ranges (p < 0.05). A multi-formula approach, according to different ranges of K and AL, could improve refractive outcomes in post-myopic-LRS eyes.

The impact of corneal higher-order aberrations on dynamic visual acuity post cataract surgery

“…Sixth, patients with history of corneal refractive surgeries are excluded from our study as the change in the morphology of cornea can cause bias in the evaluation of both HOAs and prediction refractive error after cataract surgery, due to inaccurate measurement of anterior keratometry and the variation of keratometric index after refractive surgery. It is necessary to use specific methods of IOL power calculation in these types of eyes ( Cione et al, 2023a ). Further studies are needed to analyze the influence of corneal HOAs on DVA in cataract patients with history of corneal refractive surgeries.…”

Accuracy of toric intraocular lens power calculation depending on different keratometry values using a novel network based software platform

“…Our study included mostly patients with mild to moderate WTR astigmatism and without previous refractive surgery. Because of imprecise anterior keratometry measurements and the variation in keratometric index after refractive surgery, specific methods of IOL power calculation are required for these types of eyes ( 26 ). Some of these formulas also need the knowledge of anterior to posterior radii ratio (A/P ratio), that is altered after keratorefractive surgery ( 27 ).…”

Comparative Analysis of the Visual, Refractive and Aberrometric Outcome with the Use of 2 Intraocular Refractive Segment Multifocal Lenses

“…Previously undergone keratorefractive procedures cause inaccurate measures of anterior keratometry and variation in keratometric index. Therefore, specific intraocular lens calculation methods are needed with different accuracy [ 18 ]. All patients underwent cataract surgery or refractive lens exchange between 2011 and 2021.…”