Comparison of Multicolored Spot Reflection Topographer and Scheimpflug-Placido System in Corneal Power and Astigmatism Measurements With Normal and Post-refractive Patients

Abstract

PURPOSE: To evaluate the repeatability of corneal power and astigmatism derived by a novel multicolored spot reflection topographer system (Cassini; i-Optics, Hague, Netherlands) and compare its agreement with a Placido-Scheimpflug system (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy) in normal and post-refractive patients. METHODS: This prospective study comprised patients who underwent myopic excimer laser refractive surgery (96 eyes) and normal patients (102 eyes). Each patient was measured three times with the Cassini and Sirius. The simulated keratometry (SimK), total corneal power (TCP), and astigmatism were recorded. The repeatability was assessed by one-way analysis of variance. The paired t test was used to compare the differences, whereas the agreement was evaluated by Bland–Altman analysis. RESULTS: All parameters obtained by the Cassini demonstrated high repeatability, except for total corneal astigmatism (TCA) in the post-refractive group. The intraclass correlation coefficients of all parameters were greater than 0.85, the correlation of variation values was less than 0.55%, and the test–retest repeatability was less than 0.85 diopters (D). The paired t test showed significant differences in steep keratometry, astigmatism, TCP, and TCA in the normal group and in J 0 , TCP, and TCA in the post-refractive group. The 95% limits of agreement (LoA) in the normal group demonstrated good agreement, except for TCP. Only J 0 and J 45 of astigmatism and TCA remained narrow for 95% LoA in the post-refractive group. CONCLUSIONS: These results suggested that the Cassini provided high repeatable measurements in corneal power and astigmatism, except the TCA of post-refractive patients. The parameters could be used interchangeably in normal patients, except for TCP, whereas only J 0 of astigmatism and J 0 , J 45 of TCA showed good agreement in post-refractive patients. [ J Refract Surg. 2019;35(6):370–376.]

Repeatability and Comparability of the Galilei-G4 and Cassini in Measuring Corneal Power and Astigmatism in Normal and Post-Refractive Surgery Eyes

“…These results are in agreement with previous studies that noted either low or moderate repeatability of posterior astigmatism measurements using both the Scheimp ug and Cassini analyzer [10,11,19,20,24]. The low repeatability may be explained by the low magnitude of posterior corneal astigmatism (Galilei mean -0.31 ± 0.12 D and -0.31 ± 0.16 D for normal and post-refractive eyes, respectively; Cassini mean -0.34 ± 0.17 D and -0.34 ± 0.17 D for normal and post-refractive eyes, respectively) as described by Kobashi [25].…”

“…As is consistent with previous results, in our study, the Galilei G4 Dual and Cassini showed high reproducibility in all corneal power measurements (simK, total, and posterior) in both normal and postrefractive eyes [10,11,[18][19][20][21][22][23]. For instance, Savini et al found the ICCs of simK, total, and posterior corneal power to be 0.999, 0.999, and 0.994, respectively, in a group of both normal and post-refractive eyes.…”

“…Kim et al furthermore assessed the repeatability of the Scheimp ug analyzer in simK, total and posterior corneal curvature measurements in both normal and post-refractive surgery eyes and found high repeatability in all measurements, except for posterior corneal astigmatism which was moderately repeatable [10]. Lu et al found high repeatability in both normal and post-refractive eyes for Cassini and Sirius (Placido-Scheimp ug) systems for simK, total corneal power and astigmatism recordings except for low repeatability in total corneal astigmatism in post-refractive eyes [20]. In comparing the ICC between Cassini and Galilei, Lee et al found high repeatability for simK power measurements in normal (0.991) and post-refractive surgery eyes (0.986), and poor repeatability in posterior corneal astigmatism measurements in both analyzers [11].…”

“…Most studies evaluating corneal topography repeatability enrolled only young, healthy patients, primarily between 18-40 years of age [11,18,19,20,22,24,26]. Our study enrolled patients with a mean age of 55 ± 18.5 years, and an age range of 21.5 and 91.5 years.…”

Toric Intraocular Lenses

“…Meanwhile, the highest precision for planning toric IOL power and axis was achieved by combining the keratometry and OCT data. In a recent study, Lu et al found that a novel multicolored spot reflection topographer system could provide high repeatable measurements in (both anterior and posterior) corneal power and astigmatism [38].…”