Comparison of the Predictive Accuracy of Intraocular lens Power Calculation After Phototherapeutic Keratectomy in Granular Corneal Dystrophy Type 2

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant disease affecting vision. Phototherapeutic keratectomy (PTK) is advantageous in removing vision-threatening corneal opacities and postponing keratoplasty; however, it potentially disturbs accurate intraocular lens (IOL) power calculation in cataract surgery. The myopic/hyperopic Haigis-L method with or without the central island has been reported; nevertheless, an optimal method has not yet been established. To compare the predictive accuracy of post-PTK IOL power calculations in GCD2, the retrospective data of thirty eyes from July 2017 to December 2020 were analyzed. All GCD2-affected eyes underwent post-PTK standard cataract surgery using the WaveLight EX500 platform (Alcon Laboratories, Inc., Fort Worth, TX) under a single surgeon. The mean prediction error (MPE) and absolute error (MAE) with the myopic/hyperopic Haigis-L and other formulas (Barrett Universal II, Barrett True-K, Haigis, SRK/T) by standard keratometry (K) and total kera-tometry (TK), where possible, were analyzed. Barrett Universal II and SRK/T were significantly superior to the myopic/hyperopic Haigis-L regarding the MPE and MAE. TK was not significantly superior to K in the same formula. In conclusion, this study suggests that the biometries and formulas, especially Barrett Universal II and SRK/T, are potentially useful in IOL power calculation in GCD2 after PTK.