Total Keratometry Measured With a Swept-Source Optical Biometer Versus Anterior Keratometry: From Planning to Postoperative Results

PURPOSE: To compare the influence of total keratometry (TK) versus anterior keratometry (K) measured with the swept-source optical biometer IOLMaster 700 (Carl Zeiss Meditec AG) on the planning of toric intraocular lenses (IOLs), and the error in predicted residual astigmatism (PRA).METHODS: This single-center retrospective study included 247 eyes of 180 patients. In eyes undergoing cataract surgery, the optimal toric IOL was calculated based on K or TK mea-sured with the IOLMaster 700. Two formulas were used to estimate IOL power: Holladay and Barrett Toric. Optimal cyl-inder power and alignment axis change induced by using TK versus K were reported. PRA by each calculation method was compared with manifest refractive astigmatism. Postopera-tive refractive astigmatism prediction error was calculated using vector analysis.RESULTS: The optimal toric IOL based on TK compared with K was different in 39.3% of cases with the Holladay formu-la and 31.6% of cases with the Barrett Toric formula. The use of TK rather than K reduced the centroid error in PRA when calculated with the Holladay formula (P < .001), but not when calculated with the Barrett Toric formula (P = .19). The against-the-rule astigmatism subgroup analysis with the Barrett Toric formula showed a statistically significant de-crease of centroid error in PRA with the use of TK compared with K (P = .01).CONCLUSIONS: TK compared with K measured with the IOL-Master 700 resulted in a change of optimal toric IOL in almost one-third of cases and decreased the error in PRA in patients with against-the-rule astigmatism.