Comparison of Central Corneal Thickness Measurements between Noncontact Specular Microscopy and Ultrasound Pachymetry

Abstract

Purpose:We compared and analyzed central corneal thickness (CCT) measurements according to the corneal thickness obtained with noncontact specular microscopy (NCSM) and ultrasound pachymetry (USP). Methods: CCT was measured in the order of NCSM and USP by a single optometrist in 120 eyes of 120 healthy subjects. The measurements were compared between the devices and the measurement agreements and correlations between the devices were analyzed. To determine if the measurements differed depending on the thickness of the cornea, the patients were divided into three tertile groups from the thinnest patient by CCT measurement using USP, and then the differences in CCT measured by the two devices were analyzed. Results: The CCT measurements using NCSM and USP were 548.25 ± 4.64 μm and 533.09 ± 35.96 μm, respectively. NCSM measurements were found to be thicker, showing statistically significant differences between the measurements (p < 0.001). The two examinations showed a high degree of correlation (r = 0.878; p < 0.01). In the three groups, the differences in CCT measurements between NCSM and USP were 12.93 ± 21.88 μm, 16.85 ± 15.89 μm, and 15.70 ± 20.46 μm, respectively, but the differences between the three groups were not statistically significant (p = 0.655). Conclusions:Our results show that although the differences in CCT measurements using NCSM and USP were consistent regardless of the corneal thickness, the CCT measurements by NCSM and USP were highly correlated. J Korean Ophthalmol Soc 2019;60 (7):635-642

Central Corneal Thickness Measurements With Different Imaging Devices: Ultrasound Pachymetry, Noncontact Specular Microscopy and Tono-pachymetry

“…Similarly, Uçakhan et al showed that CCT measured with USP was 20 µm higher on average than that measured using SM ( 14 ). Contrary to the other studies, Ohn et al showed that CCT measured by USP and SM were compatible and SM measured CCT 15 µm thicker than that measured by USP (p<0.001) ( 16 ). Similarly, Scotto et al found that the CCT measurement with SM was 10 µm thicker than that with USP on average ( 19 ).…”

“…In previous studies, USP and devices that can measure CCT using different methods were compared and different results were obtained. While some studies showed that CCT is measured thicker by USP than by other devices ( 11 – 14 ), it has also been shown in other studies that CCT is measured thinner by USP ( 15 , 16 ). Even in a study comparing two different USP devices, the agreement between two different pachymeters was found as poor despite a statistically significant strong correlation ( 17 ).…”