Accuracy of intraocular lens power calculation methods when targeting low myopia in monovision

To investigate the accuracy of IOL power calculation methods for refractive targets of myopia compared with emmetropia.

Lions Eye Institute, Perth, Australia.

Retrospective analysis.

Patients undergoing bilateral, sequential cataract surgery with a plan of modest monovision were analyzed. Target refraction was plano (distance eye) and -1.25 diopters (D) (near eye). Prediction error was determined by comparing the actual postoperative refraction with the predicted postoperative refraction, calculated by the Barrett Universal II (BUII), Hill-RBF version 2.0 (Hill-RBF 2.0), Haigis, Holladay 1, SRK/T, and Hoffer Q formulas. The dataset was divided into distance and near eye subgroups. Mean and median absolute error and percentage of eyes within ±0.25, ±0.50, ±0.75, and ±1.00 D of refractive target were compared.

The study included 88 consecutive patients. There was a consistent trend for lower refractive accuracy in the near eyes. BUII and Hill-RBF 2.0 were the most accurate overall and least affected by this phenomenon, with 1 (1.1%) and 4 (4.6%) fewer eyes, respectively, in the near subgroup achieving ±0.50 D of target. Haigis and SRK/T were most affected, with 14 (15.9%) and 11 (12.5%) fewer near eyes achieving ±0.50 D of target (P < .05). Holladay 1 and Hoffer Q occupied the middle ground, with 6 (6.8%) and 9 (10.2%) fewer near eyes achieving ±0.50 D of target.

IOL-power calculation formulas appear to be less accurate when targeting myopia compared with emmetropia. BUII and Hill-RBF 2.0 represented good options when planning pseudophakic monovision as they were least affected by this phenomenon and can be used for both distance and near eyes.