Measuring Corneal Astigmatism Using Optical Coherence Tomography in Keratoconus

Purpose: To measure net corneal astigmatism using optical coherence tomography (OCT, Avanti, Optovue) in individuals with keratoconus and compare its repeatability and accuracy with those obtained using Scheimpflug imaging (Pentacam HR, Oculus). Setting: Casey Eye Institute, Portland, Oregon, USA. Design: Prospective cross-sectional observational study. Methods: Net corneal astigmatism was calculated in keratoconic and normal eyes with OCT and Scheimpflug imaging using four settings - pupil or vertex centration settings with a 3 or 4 mm circular analytical zone. Corneal elevation maps were obtained from OCT images and fitted with Zernike polynomials to obtain net corneal astigmatism. Manifest refraction astigmatism was used ...