Purpose:

The Barrett True-K and ASCRS IOL calculator are the gold standard in post-refractive IOL calculations without historical data. However, we only achieve +/- 0.50D 63-74% of the time. This study will evaluate the use of IOL master 700 Total Keratometry (TK) and the Barrett True-K-TK vs other formulae to improve post-refractive IOL calculations.

Methods:

A retrospective comparative case series was performed for n=27 post myopic LASIK/PRK patients undergoing uncomplicated cataract surgery. Four formula were compared including Haigis L, Shammas, Barrett True-K and Barrett True-K TK. Biometry was performed with the IOL master 700. The Barrett True K-TK was calculated using the IOL master 700 posterior cornea measurements (PK1 and PK2) and displayed by using the TK upgraded software. The outcome measures included Mean and Median Absolute error and percentage of predicted refractive error within 0.5D and 1.0D.

Results:

Mean absolute error(MAE)for Haigis L was 0.44D, SD 0.33D; Shammas was 0.39D, SD 0.34D; Barrett True-K was 0.31D, SD 0.26D; and Barrett True-K TK was 0.28D, SD 0.21D. Median absolute error (MedAE) was the following: Haigis L 0.38D; Shammas 0.24D; Barrett True-K 0.24D; and Barrett True-K TK 0.28D. Predicted error within +/-0.50D and +/-1.0D was the following: Haigis L 63%,92.5%; Shammas 70%,96%; Barrett True-K 77%,100%; and Barrett True-K TK 88%,100%, respectively.

Conclusions:

Barrett True-K TK improved the percentage of patients with prediction errors within +/- 0.50D by 10% compared to the Barrett True-K with standard K's. The use of the IOL master 700 total keratometry and calculated posterior corneal curvature (PK1 and PK2) measurements resulted in improved accuracy for post-refractive IOL calculations.