Envisu system

For OCT images captured by Bioptigen Envisu system, averaged radial scan images were used for retinal thickness measurement. For each eye, measurements were performed on four spots (450 μm from center of ONH at both horizontal and vertical directions) using vendor provided Reader program (Bioptigen), and the averaged number was used as the measurement for the eye. Total retina thickness was measured from nerve fiber layer (NFL) to basal side of RPE layer (Bruch's membrane [BM]). Outer retina length was measured from outer limiting membrane (OLM) to BM, two clearly distinguishable OCT layers even for degenerative retina. The same four spots were also used to calculate intensity profile across the outer retina based on averaged value of 10-pixel width at the spot center of OCT images. The width of EZ (IS/OS) (the inner segment ellipsoid zone, also referred as the inner segment/outer segment [IS/OS] junction^{10 (link),25 (link)–27 (link, link)}) was calculated from mid-point of ascending and descending phases on intensity profile of the band (as illustrated in Fig. 1). For OCT images captured with Heidelberg Spectralis, the frame of OCT B-scan that showed the largest subretinal fluid accumulation from each eye was selected for analysis. The highest values of outer retina length (from OLM to BM) were measured. Data are presented as mean ± SEM.