The precision and agreement of corneal thickness and keratometry measurements with SS-OCT versus Scheimpflug imaging

Purpose:To assess the repeatability and reproducibility of swept-source optical coherence tomography(SS-OCT)and Scheimpflug system and evaluate the agreement between the two systems in measuring multiple corneal regions in children.Methods:Pachymetric and keratometric maps for both systems were evaluated.Central,midperipheral and peripheral corneal thickness(CT),keratometry and astigmatism power vectors were recorded.The three outcomes yielded by the same observer were used to assess intraobserver repeatability.The differences in the mean values provided by each observer were used to evaluate interobserver reproducibility.Within-subject standard deviation,test-retest repeatability(TRT)and coefficient of variation(CoV)were used to analyze the intraobserver repeatability and interobserver reproducibility.Paired T-test and Bland-Altman were used to appraise interdevice agreement.Results:Seventy-eight eyes of 78 children were included.The CoV was≤2.12 and 1.10%,respectively,for repeatability and reproducibility.TRT and CoV were lower for central and paracentral CT measurements than for peripheral measurements.The SS-OCT device generated higher precision when acquiring CT data,whereas Scheimpflug system showed higher reliability when measuring corneal keratometry.Although the CT readings measured using SS-OCT were significantly thinner than Scheimpflug device(P<0.001),the central and thinnest CT values were still of high agreement.The interdevice agreement of keratometry measurement was high for the central corneal region and moderate for the paracentral and peripheral areas.Conclusions:The precision of CT measurements by SS-OCT was higher,while the reliability of keratometry measurements by the Scheimpflug system was higher in children.Apart from the measured values in the central corneal region,the thickness and keratometry readings should not be considered interchangeable between the two systems.