Repeatability and Accuracy for Detecting Ectatic Diseases of Corneal Epithelial Thickness Measurements From Fourier-Domain OCT
Narrative Responses:
Purpose
To evaluate the repeatability of corneal epithelial thickness measurements from Fourier domain optical coherent tomography (FD-OCT; RTVue, Optovue, Fremont, CA) on normal, forme fruste keratoconus (FFKC) and keratoconus (KC).
Methods
One eye randomly selected from 10 normal and from 10 keratoconus patients, and from 10 eyes with forme fruste keratoconus were included. FFKC criteria was the fellow eye with normal topography from patients with very asymmetric keratoconus. The minimum, maximum, central, superior and inferior epithelial thickness values were computed for the central 6mm zone. For each eye, 5 consecutive measurements were taken by the same observer using the RTVue. The standard deviation (repeatability [SD]) and coefficient of variation (CV [SD divided by average]) of the 5 consecutive measurements taken for each parameter.
Results
The repeatability (SD) for the normal, keratocons and FFKC groups were respectively: 1.19, 2.22 and 0.752 for minimal; 0.742, 1.175 and 1.595 for maximal; 0.639, 1.6 and 1.166 for central; 0.71, 0.879 and 0.846 for superior; 0.627, 1.161 and 0.907 for inferior; and 0.322, 0.306 and 0.415 for the variation of epithelial values. The CV for the normal, keratocons and FFKC groups were respectively (%): 2.838, 5.893 and 1.626 for minimal; 1.295, 1.894 and 2.761 for maximal; 1.224, 3.199 and 2.245 for central; 1.412, 1.6 and 1.631 for superior; 1.206, 2.285 and 1.743 for inferior.
Conclusion
OCT RTVue was found to be very precise with less than 2 microns of repeatability for minimum, maximum, central, superior and inferior corneal epithelial thickness values on the central 6mm zone. Corneal epithelial measurements should be tested for their accuracy for detecting ectatic diseases.