Mapping of corneal birefringence in thin and asymmetric keratoconus corneas with ultrahigh-resolution polarization-sensitive OCT

Abstract

Purpose:To evaluate phase retardation (PR) across healthy eyes and eyes with thin corneas (<500 m) and with asymmetric and bilateral keratoconus (KC).Setting:Narayana Nethralaya Eye Hospital, Bangalore, India.Design:Observational cross-sectional.Methods:There were 4 eye groups: healthy eyes (Group 1; n = 10 eyes), eyes with thin corneas and no clinical disease (Group 2; n = 10 eyes), eyes with asymmetric KC (Group 3; n = 5 eyes), and eyes with clinical KC (Group 4; n = 15 eyes). All eyes were imaged with polarization-sensitive optical coherence tomography (PS-OCT), MS-39, and Corvis-ST. Using PS-OCT, PR was analyzed in annular regions. The anterior (A-E) and Bowman (E-B) wavefront aberrations, epithelial Zernike indices (EZI), total corneal thickness, Corvis biomechanical index (CBI), total biomechanical index (TBI), and Belin-Ambrósio overall deviation index (BAD-D) were analyzed.Results:Only CBI, TBI, BAD-D, A-E and E-B aberrations, EZI, and total corneal thickness distributions of Groups 1 (n =10), 2 (n =10), and 3 (n =5) were similar (P >.05) but not CCT (P