Comparison of central corneal thickness measured by noncontact tonometry and ultrasound pachymetry

Abstract

PurposeTo compare and analyze central corneal thickness (CCT) as measured by ultrasound pachymetry(USP) with noncontract tonometry(NCT) TX‐20P, which involves the function to measure central corneal thickness.MethodsThe central corneal thickness was measured in 45 eyes of 26 glaucoma patients and in 84 eyes of 43 healthy patients by two optometrist. First, noncontact tonometry TX‐20P was used to measure the CCT, followed by measurements taken using ultrasound pachymetry later. The results were compared and the correlations between two devices were analyzed. To determine whether the measurements vary depending on use of anti‐glaucoma eyedrops, all subjects were classified into two groups. Then, the difference of the CCT measured by the two devices was analyzed.ResultsThe average measurements of central corneal thickness using ultrasound pachymetry and noncontact tonometry TX‐20P were 529.07 ± 40.40 μm and 526.26 ± 35.30 μm, respectively. The central corneal thickness by ultrasound pachymetry was thicker than by noncontact tonometry TX‐20P. There was statistically significant differences between the measurements (p < 0.001) and the two exams showed high degree of linear correlation(r = 0.919, p < 0.001). The difference of central corneal thickness between two devices was 2.80 ± 19.00 μm in group 1 and 2.81 ± 14.29 μm in group 2. The difference between two groups was not statistically significant (p = 0.997).ConclusionsThis study showed that the results using ultrasound pachymetry and noncontact tonometry TX‐20P had significant positively correlation with each other regardless of using anti‐glaucoma eyedrops.