Accuracy of OCT-derived net corneal astigmatism measurement

PURPOSE: To assess the repeatability and accuracy of corneal astigmatism measurement with a spectral-domain optical coherence tomography (OCT) system (Avanti, Optovue) and compare them with Scheimpflug imaging (Pentacam HR, Oculus) and swept-source optical biometry (IOLMaster 700, Carl Zeiss Mediatec AG). SETTING: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, USA DESIGN: Prospective cross-sectional observational study. METHODS: Sixty pseudophakic eyes with monofocal non-toric intraocular lens that previously had refractive surgery were analyzed. To assess accuracy, simulated keratometric (SimK) and net corneal astigmatism, obtained from each device were compared with subjective manifest refraction astigmatism. Repeatability for corneal astigmatism was assessed for OCT and Pentacam HR by the coefficient of repeatability from three repeated measures. RESULTS: Compared to manifest refraction, SimK readings produced with-the-rule (WTR) astigmatic bias which was reduced for net astigmatism for all the three devices. Except for OCT net astigmatism, all instruments significantly overestimated the magnitude of the astigmatism (linear mixed-effects model (LMM), P < .05). OCT net astigmatism showed the highest accuracy for manifest astigmatism prediction with the smaller 95% confidence ellipse for the mean difference vector. OCT net mean absolute difference was 0.57 D, significantly smaller than that of the other modalities (LMM, P