[Calculation of intraocular lens power in surgical treatment of extreme hyperopia].

Abstract

Accuracy of calculation of the intraocular lens (IOL) power in eyes with short axial length is inferior to one in emmetropic eyes. Most studies focus on relatively standard eyes. To assess the accuracy of power calculation for IOL used to correct extreme hyperopia and to compare available formulas based on their predictive capacity. Results of 13 implantations involving IOLs of at least 40 Diopters (D) in power were retrospectively evaluated. IOL power was calculated using five formulas: Haigis, Hoffer Q, HolladayI, SRKII, SRK/T. Mean numerical refractive prediction error (RPE) and mean absolute refractive prediction error (ARPE) were calculated. Mean and median ARPE were computed after optimizing the A0 constant. Proportions of eyes within certain RPE limits were compared between the formulas. Mean RPE ranged from 1.43 to 11.71 D before adjustment and from 1.08 to 5.34 D after adjustment (p<0.0001). Haigis formula produced the least RPE, and SRKII - the most. Pairwise comparison by mean ARPE after adjustment revealed no statistically significant difference between Haigis and Hoffer Q formulas. Comparison of formulas by percentage of eyes with minimal RPE identified Haigis and Hoffer Q as the most accurate, while the difference between the two was not statistically significant. The difference between the most accurate formulas (Haigis and Hoffer Q) and the least accurate (SRKII) was statistically significant. In eyes with extremely short anterior-posterior axis, prediction errors in IOL power calculations are relatively frequent (only 31-46% of eyes are within ±0.5 D) and warrant reduction. Among the evaluated formulas, Haigis and Hoffer Q are the most accurate. In order to improve the accuracy of IOL power calculations, it is necessary to employ personalized constants.