Repeatability and comparability of the Galilei-G4 and Cassini in measuring corneal power and astigmatism in normal and post-refractive surgery eyes

Abstract

To assess the repeatability and comparability of the Galilei G4 versus the Cassini topographer in post-refractive eyes and in normal eyes, including older patients representative of an initial cataract evaluation. Simulated keratometric (simK), total corneal and posterior corneal power and astigmatism were evaluated in both post-refractive and normal eyes. Repeatability was measured by calculating within-subject standard deviation (Sw), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). Vector analyses and Bland–Altman plots were employed to assess agreement between devices. We studied 32 subjects with a history of refractive surgery and 32 subjects without a history of refractive surgery undergoing cataract surgery. The mean age was 55 ± 18.5 years and the age range was 21.5–91.5 years. In non-refractive and post-refractive eyes, the ICC was > 0.9 (P < 0.001) for all corneal powers and for simK and total corneal astigmatism for both analyzers. The ICC for posterior corneal astigmatism magnitude using the Galilei was 0.62 and 0.67 and for the Cassini 0.55 and 0.38 in normal and post-refractive eyes, respectively. In both post-refractive and normal eyes, the Galilei G4 and Cassini analyzers have high repeatability in simK, total, and posterior corneal power and low repeatability for posterior corneal astigmatism.

Ray tracing optimization: a new method for intraocular lens power calculation in regular and irregular corneas

“…Multiple studies described the excellent repeatability and reproducibility of corneal topography measurements provided by different types of imaging systems [40][41][42][43] . There is some kind of controversy, however, about the reported repeatability for some corneal parameters after corneal refractive surgery 44 , as well as in patients with dry eye 45 , keratoconus 46 and patients at the typical age for cataract 47 . The statistical uncertainty of the elevation measurements also increases toward the peripheral area, but the central 6-mm region may be considered as www.nature.com/scientificreports/ reliable [48][49][50][51] .…”