Accuracy of optical coherence tomography (OCT) in pachymetry for glaucoma patients

Abstract

BackgroundCentral corneal thickness (CCT) measurement has become an important test in the diagnosis and management of glaucoma. Currently, ultrasound corneal thickness measurement (pachymetry) is the most frequently used clinical technique and the gold standard to assess CCT. Newer instruments are currently available including the optical coherence tomography (OCT) instrument. The aim of the present study was therefore to evaluate the accuracy of the CCT measurements performed by three different observers, both with the OCT and ultrasound pachymetry (USP), in patients suffering from glaucoma.MethodsPatients who had been previously diagnosed with glaucoma participated in this cross-sectional study. Glaucoma was defined as patients who had at least two repeatable Humphrey visual fields showing glaucoma damage using the software 24–2, and with the optic nerve showing typical glaucoma damage. The patients CCTs were measured with OCT and USP by three different examiners.ResultsSeventy eyes of 35 patients were included. The average age was 74 ± standard deviation (SD) 10.88, the average pachymetry value with OCT was 536 ± 29 μm, and the average pachymetry with USP was 532 ± 32 μm. The differences between OCT and USP were not significant (t-test, p = 0.32). The intraclass correlation coefficients were, for OCT, 0.99 [confidence interval (CI): 0.98–0.996], and for USP, 0.97 (CI: 0.95–0.98).ConclusionsAgreement among the three observers using OCT or USP for pachymetry measurements was good. OCT might be used as an alternative method for pachymetry in glaucoma patients.

Comparison of central corneal thickness by ultrasound pachymetry, optical coherence tomography and specular microscopy

“…Shetgar et al [1] found the mean CCT for glaucoma patients to be 503.91 ± 11.31 μm using ultrasound pachymetry. Ayala et al [5] Additionally, there was a strong correlation between each of the three techniques, especially between OCT and specular microscopy, where r 2 =0.98. Among the various comparisons, the weakest correlation was found between ultrasound pachymetry and specular microscopy (r 2 =0.88), but this correlation was statistically significant.…”

No differences in central corneal thickness between open-angle and pseudoexfoliation glaucoma patients

“…There is also a report by Adibelli et al,51 showing a significant difference between OCT and USP in 26 POAG patients, where mean CCT was higher with OCT compared to USP. Comparison by Ayala and Strandås50 between OCT and USP did not show any difference between these two devices. However, this might be a reason for different outcomes when measuring CCT worldwide.…”

“…The opposite, overestimation with OCT compared to USP has also been reported 50,51. Wells et al48 compared optical pachymetry, OCT and ultrasound, and found that these devices are not interchangeable in clinical practice.…”

Study of central corneal thickness using non-contact techniques: Specular microscopy (Nidek CEM-530), corneal tomography (Pentacam HR), and optical coherence tomography (Cirrus HD-OCT 5000) in healthy adult patients

“…Furthermore, the algorithms employed by different devices for corneal thickness calculation may provide slightly different pachymetric values. Other authors have found that measurements obtained with Cirrus HD-OCT are greater than those provided by contact ultrasonic pachymetry (11,20).…”

“…This study compares central corneal pachymetry values obtained with several non-invasive devices. There are multiple previous publications that analyses the correlation between different devices (10)(11)(12)(13)(14).…”