Intraocular lens power calculation using a Placido disk-Scheimpflug tomographer in eyes that had previous myopic
Giacomo Savini1, Kenneth J Hoffer1, Domenico Schiano-Lomoriello1
1From the G.B. Bietti Foundation IRCCS (Savini, Schiano-Lomoriello), Rome, Italy; Stein Eye Institute (Hoffer), University of California, Los Angeles, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA; Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy.
Purpose:
To assess the accuracy of different methods to calculate the intraocular lens (IOL) power from measurements obtained with an optical biometer combined with a Placido disk-Scheimpflug tomographer (Galilei G6) in eyes that had previous myopic excimer laser surgery.
Setting:
G.B. Bietti Foundation, Rome, Italy.
Design:
Prospective case series.
Methods:
When prerefractive surgery data were available, the following methods were evaluated: the Barrett True-K, total corneal power 1 (TCP 1) with double-K SRK/T, TCP with double-K Holladay 1, as well as the Masket and Savini methods. In all eyes, these "no-history" methods were studied: Barrett True-K No-History, TCP 1 using the American Society of Cataract and Refractive Surgery calculator, a ray-tracing program, and the Shammas No-History formula.
Results:
In eyes with historical data (n = 15), the Masket method, Savini method, and TCP 1 with double-K SRK/T produced the highest percentage of cases with an absolute prediction error in refraction of 0.50 diopters (D) or less and the lowest median absolute error (0.32 D, 0.28 D, and 0.25 D, respectively). In the whole cohort (N = 22), the most accurate no-history method was paraxial ray tracing, which had the highest percentage of eyes with an absolute prediction error of 0.50 D or less and the lowest median absolute error of 0.31 D.
Conclusion:
Different solutions can provide accurate IOL power calculations when using the measurements obtained with the optical biometer combined with a Placido-dual Scheimpflug tomographer.
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