Evaluating the Predictive Accuracy of the Kane and SRK/T Formulas in Keratoconus Patients Undergoing Cataract Surgery

To compare the predictive performance of the SRK/T and Kane formulas in eyes with keratoconus undergoing cataract surgery.

A consecutive series of keratoconic eyes that underwent cataract surgery were retrospectively analyzed. Intraocular lens power was calculated using the SRK/T and Kane Keratoconus formulas. Subjective refraction was evaluated 1 month postoperatively. The mean prediction error (MPE) and percentage of eyes with a prediction error within ±0.50 diopters (D) and ±1.00 D were calculated. Patients were divided into two categories: early-stage (stage 1) and advanced-stage (stage 2-3) keratoconus.

Thirty eyes of 25 patients were included in the study. A comparison of MPE between the two formulas in the stage 1 keratoconus group revealed no statistical difference. However, the MPE for the SRK/T formula was found to be significantly higher (p=0.005) in the stage 2-3 group. In the stage 1 group, 84.6% of eyes were within the PE range of ±1.00 D based on the Kane formula, while 76.9% of eyes fell within the ±1.00 D range according to the SRK/T formula. In stage 2-3 group, 41.2% of eyes were within the PE range of ±1.00 D based on the Kane formula, while 29.4% of eyes fell within the ±1.00 D range according to the SRK/T formula.

A comparison of the two formulas showed no statistically significant differences in early-stage keratoconus. However, in advanced keratoconus cases, the Kane formula exhibited superior accuracy.