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Comparison of central corneal thickness measurements with three non-contact pachymeters and a standard ultrasonic pachymeter

Poster Details

First Author: E.Şenel TURKEY

Co Author(s):    M. Durmus              

Abstract Details


To compare central corneal thickness (CCT) measurements obtained by non-contact AL-Scan (AL-S), Sirius Scheimpflug Topography (SST), Non-contact pachytonometer (NCP) and conventional contact ultrasound pachymetry (UP) in healthy corneas.


The study was conducted in Ophthalmology Department of Hitit University, Corum, Turkey.


In this prospective study, CCT was measured in 144 eyes of 72 healthy subjects. Results were analyzed statistically by interclass correlation (ICC) coefficient to measure the correlation between all pachymeters. Bland-Altman were used to assess agreement among the instruments, and 95% limits of agreement (LoA) for each comparison were calculated.


The mean CCT by AL-S, CST, UP and NCP were 534.92±42.79 µm (range: 438-631), 545.20±43.08 µm (range: 444-634), 554.20±45.94 µm (range: 449-674), 563.08±43.97 µm (range: 464-665), respectively. The mean differences for CCT measurements were 28.1 µm between NCPachytonometer and AL-Scan optic biometer (ICC:0,970), 17.8 µm between NCP and SSTopography (ICC:0,968), 8.8 mm between NCP and Ultrasound pacymeter (ICC:0,966), 10.2 µm between AL-S and CST (ICC:0,987), 19.2 µm between AL-S and UP (ICC:0,976), and 9 mm between CST and UP (ICC:0,968). The Bland–Altman analysis better shows the clinical relevance of repeatability between the four instruments.


The correlation is significant between all devices (p<0.01). The best correlation was calculated between AL-S and CST. AL-S and CST consistently measuring lower than ultrasound. NCP measured the highest CCT values. Although CCT values obtained with AL-S, CST, NCP and UP show a good correlation, it should be noted that these devices are not completely interchangeable in clinical practice. FINANCIAL DISCLOUSRE: NONE

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