gms | German Medical Science

Purpose: To compare measurements of corneal indices using Placido-dual rotating Scheimpflug (PDRS), swept-source optical coherence tomography (SS-OCT), and Placido-slit scanning (PSS) systems.

Methods: Fifty normal eyes (normal group) and 50 post-refractive surgery eyes (refractive group) were included. Corneal topography measurements were performed using PDRS (Galilei G2, Zeimer),SS-OCT (Casia SS-1000, Tomey), and PSS (OrbscanIIz, Bausch&Lomb). The intraclass correlationcoefficients (ICC) and Bland-Altman plots were used to evaluate the agreement.

Results: The agreement among the three devices in terms of anterior keratometry, best-fit sphereradius and pachymetry was high (ICC>0.9) in both group. Posterior keratometry and eccentricity inboth group had high ICC values between PDRS and SS-OCT (>0.9), but not PSS when compared with theother two devices. PSS exhibited much steeper values for posterior keratometry (P<0.05) in bothgroup. The ICC values for posterior corneal elevation were lower than 0.9 among all three devices, PDRS and PSS showed relatively higher ICC than with the PSS in both group. Maximum posteriorelevation were highest for PSS (38.96±9.53 μmnormal group, 44.98±11.36 μmrefractive group), followed by SS-OCT (10.60±3.30 μmnormal, 10.94±4.03 μmrefractive group), and PDRS (8.84±3.92 μmnormal group, 9.38±3.50 μmrefractive group).

Conclusions: The anterior keratometry and pachymetry obtained using three different devices showedhigh degrees of agreement. Posterior keratometry and eccentricity showed greater agreement between PDRS and SS-OCT than with the PSS system. PDRS and SS-OCT were equivalent in detecting the shape of the cornea and could be considered interchangeable.