Abstract
Purpose: :
To determine reproducibility and compare mean values of central corneal thickness obtained using contact ultrasound pachymetry, the Artemis-2 ultrasound arc-scanner, and Visante Optical Coherence Tomography.
Methods: :
The central corneal thickness of 20 eyes (10 healthy subjects) was measured using three different modalities. Three consecutive contact pachymetry values were performed on both eyes and the mean value was recorded. We then performed Visante OCT corneal pachymetry maps on each eye. Lastly, Artemis-2 scans were performed with duplicate corneal maps (generated from six scans, one for each clock-hour). We recorded the minimum central corneal thickness values from the Visante OCT and Artemis-2 maps. We then determined differences in corneal thickness between techniques and standard deviations for repeated measurements of the same eye. We compared the results statistically using ANOVA, correlation analysis, and Bland-Altman plots.
Results: :
The standard deviations for multiple measurements of the same eye were 0.7 microns for Artemis-2, 3.2 microns for contact pachymetry, and 2.5 microns for Visante OCT. The mean differences between techniques + SD were 1.9+10.6 microns (Visante OCT-Artemis-2), 25.2+8.4 microns (pachymeter - Artemis-2), and 23.8+8.2 microns (pachymeter - Visante OCT). One way ANOVA showed a significant difference between the three different modalities of measuring central corneal thickness (F=5.39, p=0.007). R2 values for correlations between the methods were: Artermis-2 versus Vistante=0.845, Artemis-2 versus pachymetry=0.867, and Visante versus pachymetry=0.899.
Conclusions: :
There was a high degree of agreement between the Visante OCT and Artemis-2 in measurement of central corneal thickness. However, contact ultrasound pachymetry values were on average approximately 24 microns thicker than both the Visante OCT and Artemis-2.
Keywords: cornea: clinical science • refractive surgery • refractive surgery: corneal topography