Abstract
Purpose :
Central corneal thickness (CCT) plays an important role in the diagnostic and therapeutic assessment of ocular pathologies. The aim of the study was to assess the comparability of central corneal thickness measurements by optical coherence tomography (OCT) and ultrasound pachymetry and to determine their reliability and interchangeability as clinical tools. Based on the universal use of both methods in clinical practice, we hypothesised there would be no significant difference between the measurements.
Methods :
We compared measurements by Optovue RTvue-100 optical coherence tomography (OCT) and Pachmate ultrasound (US). The data for OCT pachymetry was collected prospectively for 112 glaucoma and glaucoma suspect patients over a 5 month period. Using Bland-Altman plots, this was compared with retrospectively collected data on previously performed ultrasound pachymetry for the same patients. The statistical tools used in the data analysis included standard deviation, standard error and confidence intervals.
Results :
A statistically significant difference was shown between pachymetry results obtained by US and OCT, with the mean difference of 26.00µm (standard error 1.72; standard deviation 18.19) and 31.13µm (standard error 1.84; standard deviation 19.39) and the 95% confidence interval of ± 3.41µm and ± 3.65µm for the right and left eye, respectively. The absolute measurement difference between the two methods was 0-135µm and 0-100µm for the right and left eye, respectively.
Conclusions :
No gold standard exists for CCT measurement. Higher US thickness may be due to off-centre readings, exacerbated by Bell’s reflex. As CCT impacts corrected intraocular pressures and monitoring corneal endothelial failure, we challenge the interchangeable use of US and OCT pachymetry in clinical settings.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.