COMPARISON OF INTRAOCULAR LENS POWER FORMULAS USING TOTAL KERATOMETRY IN EYES WITH A HISTORY OF HYPEROPIC LASER IN SITU KERATOMILEUSIS

This study aimed to evaluate the performance of two modern IOL power formulas in eyes with a history of hyperopic LASIK undergoing subsequent cataract surgery, and determine whether using total keratometry (TK) affects the prediction accuracy.

Cathedral Eye Clinic, Belfast, Northern Ireland 

Forty-seven eyes of 25 patients that had undergone hyperopic LASIK and subsequent cataract surgery were included in the study. Refractive prediction error and percentages of eyes with absolute prediction error within 0.25D, 0.50D, 0.75D and 1.00D were calculated for Barrett True K, Barrett True K TK, EVO and EVO TK for all eyes. TK data was obtained from an optical biometer (IOLMaster 700, Carl Zeiss Meditec).

The median absolute error (MAE) was 0.459, 0.441, 0.416 and 0.401D for Barrett True K, Barrett True K TK, EVO and EVO TK respectively. Root mean square error (RMSE) was 0.544, 0.526, 0.536 and 0.516D for Barrett True K, Barrett True K TK, EVO and EVO TK respectively. EVO had the highest proportion of eyes within 0.50D and 1.00D (70% and 94% respectively). For eyes with TK data available, a higher proportion of eyes within 0.50D was achieved when total keratometry was used compared to standard keratometry for Barrett True K (60% vs 53%) but not for EVO (66% vs 70%).

The EVO TK formula achieved the lowest MAE and RMSE in these eyes with a history of hyperopic LASIK. Using total keratometry improves the overall prediction accuracy of Barrett True K and EVO, although it did not significantly increase the proportion of eyes within 0.50D for EVO.