Refractive outcomes of intraocular lens power calculation using different corneal power measurements with a new optical biometer

Purpose: To evaluate the results of intraocular lens (IOL) power calculation using different comeal power measurements provided by an optical biometer combined with a dual Scheimpflug analyzer and a Placido disk topographer (Galilei G6). Setting: G.B. Bietti Foundation, Rome, Italy, and Keio University Hospital, Tokyo, Japan. Design: Evaluation of diagnostic technology. Methods: Consecutive patients having cataract surgery were enrolled. The IOL power was calculated with the Barrett Universal II, Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Different options were used to calculate the corneal power: simulated keratometry (K) based on anterior comeal surface measurements only and total comeal power (TCP) based on ray tracing through both corneal surfaces. Three TCP measurements (TCP1, TCP2, and TCP-1014 were evaluated. Results: The study analyzed 118 eyes. The mean values of simulated K (43.74 diopters [D] +/- 1.40 [SD)), TCP1 (43.13 +/- 1.35 D), TCP2 (41.87 +/- 1.30 D), and TCP-IOL (42.62 +/- 1.35 D) were significantly different (P <.0001). The best results were obtained using simulated K: the median absolute error ranged between 0.22 D and 0.29 D and the percentage of eyes with a prediction error of +/- 0.50 D or less, between 76.2% and 84.7%, depending on the formula. After constant optimization, the results using any TCP value and simulated K were similar with no statistically significant differences. Conclusions: Biometric measurements provided by the Scheimpflug Placido optical biometer can be used to accurately calculate the IOL power. Simulated K and TCP led to similar outcomes after constant optimization. (C) 2018 ASCRS and ESCRS.