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Repeatability of posterior keratometry measurements obtained with swept-source optical coherence tomography and comparability to measurements using scheimpflug-based tomography

Poster Details

First Author: D.Cui USA

Co Author(s):    D. Cui   A. Poulsen   A. Lu   C. Seeger   I. Scott   S. Pantanelli     

Abstract Details


Optimal intraocular lens power selection for cataract surgery depends upon accurate pre-operative keratometry measurements. Traditional reflectance keratometry is based on anterior corneal surface measurements (K). Recently, the IOLMaster 700 gained the capability to measure posterior corneal curvature (PK) and total keratometry (TK) using swept-source optical coherence tomography (SS-OCT). The purpose of this study is to investigate the repeatability of PK and TK measurements obtained from SS-OCT relative to reflectance keratometry based Ks, and to compare these measurements to values obtained using a combined dual-Scheimpflug Placido-based tomographer/topographer.


Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania, USA of America.


Patients undergoing cataract surgery evaluation between January 2019 and February 2020 were prospectively enrolled. Exclusion criteria included prior ophthalmic surgery, ocular trauma, keratoconjunctivitis sicca, and pathology known to affect the cornea's shape or regularity. Participants underwent three measurements using the reflectance/SS-OCT biometer (IOLMaster 700, Carl Zeiss Meditec) and one measurement using the dual-Scheimpflug Placido disc corneal tomographer/topographer (Galilei G4, Zeimer). Intra-device repeatability for K, PK, and TK on the SS-OCT device were evaluated using within-subject standard deviations, coefficients of variance, test-retest repeatability, and intraclass correlation coefficients. Agreement between devices was assessed with Pearson’s correlation coefficients and Bland-Altman analyses.


Eighty-two eyes from 48 patients met inclusion criteria. The mean within-subject standard deviation (Sw) was 0.12 D for the mean K and 0.03 D for the mean PK. Sw was 14.94 for anterior steep axis and 11.65 for posterior steep axis. Sw for the delta TK was 0.23 D and 16.8 degrees for the magnitude and axis, respectively. Bland-Altman analysis indicated a high level of agreement and probable interchangeability for K measurements, but only moderate agreement and a lack of interchangeability for PK measurements. The IOLMaster 700 reported consistently flatter posterior corneal curvatures than the Galilei G4 (p=0.0001).


PK measurements are more repeatable than K measurements using the SS-OCT biometer. PK measurements with the SS-OCT biometer and Scheimpflug-Placido disc tomographer/topographer are moderately correlated, but should not be considered interchangeable.

Financial Disclosure:

receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented

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