IOL Power Calculation in the Elderly Population Using the Kane Formula in Comparison to Existing Methods

PURPOSE To assess the accuracy of the Kane formula for intraocular lens (IOL) power calculation in comparison to established formulas in the elderly population. SETTING Shiley Eye Institute, University of California San Diego, USA. DESIGN Retrospective cohort. METHODS Retrospective data from 90 patients ≥75 years old who underwent uneventful cataract surgery with SN60WF IOL implantation were evaluated. The first operated eyes of patients with final best-corrected visual acuity 20/40 or better and axial length 22-26 mm were included. Prediction errors were calculated for Barrett Universal II (BUII), Haigis, Hoffer Q, Holladay 1, Kane and SRK/T formulas. A subgroup analysis based on age (75-84 and ≥85 years old) was performed. RESULTS Use of both BUII and Kane formulas resulted in the highest percentage of eyes with prediction errors within ±0.50 D (72% each) and significantly higher than Hoffer Q, Holladay 1 and SRK/T (p=0.001). Rates of predictability within ±0.25 D and ±1.00 D were 31%-38% and 87% -92%, respectively, with no significant differences between formulas. No statistically significant difference was seen between formulas in the median absolute error. These tendencies remained consistent in both age groups when analyzed separately. Subgroup analysis showed better predictability of all formulas in the younger age group. CONCLUSIONS This is the first study evaluating the Kane formula exclusively in the elderly population. The Kane formula was found to be of equal accuracy to the BUII and superior to the Hoffer Q, Holladay 1 and SRK/T formulas. Very elderly patients may have reduced refractive precision using all formulas.