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Repeatability of topographic corneal thickness in keratoconus comparing Visante™ OCT and Oculus Pentacam HR®
Heinz Otchere1, Luigina Sorbara1
1School of Optometry & Vision Science, Centre for Contact Lens Research, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
Purpose:
To assess the repeatability and reproducibility of Visante™ OCT and Oculus Pentacam HR® in measuring central (CCT) and topographic corneal thickness (TCT) along the principle meridians in keratoconus (KC) corneae.
Method:
Twenty participants diagnosed with KC were recruited. There were two study visits. On the first study visit, two repeated corneal thickness measurements were obtained with each instrument. Measurements were repeated at least 48hrs later in the same order. TCT were recorded in the 90, 180, 45 and 135 meridians at 1mm intervals across 8mm chord.
Results:
Mean CCT for Visante™ OCT was 484.97±43.14μm (range: 484.84-486.09) and Oculus Pentacam HR® was 478.86±45.31μm (range: 477.20-480.53). No significant difference in TCT between the two visits (p=0.54) and measurements (p=0.63) for Visante™ OCT. For Oculus Pentacam HR®, no significant difference was found for each visit (p=0.18) but differences existed in the measurements outside of the central region (p=0.001). Tukey post-hoc analysis shows the differences (p˂0.05) were found in the +1 and +4 (supero-temporal) locations in the 135 meridian. Significant differences were found comparing the two instruments, (p<0.05). Bland Altman plots were used to demonstrate the differences between the two instruments and indicate their limits of agreement.
Conclusion:
Both instruments gave repeatable measurements as no significant differences were found in most locations in all meridians. Comparing the two instruments, they were not reproducible in all locations.
