The 360° circumferential opening of Schlemm's canal in normal individuals detected by enhanced depth imaging optical coherence tomography

We aimed to observe the opening status and morphological parameters of Schlemm's canal (SC) in normal eyes using enhanced depth imaging optical coherence tomography (EDI-OCT). Consecutive EDI-OCT scans were used to examine the right eye of 20 normal individuals. EDI-OCT was performed clockwise for 8 regions (at the 12:00, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00 and 10:30 o’clock positions). Image processing and analysis in java software was used to measure the area, perimeter, and diameter of SC. Twenty-one serial scans of each region were evaluated and a total of 168 images were included in the analyses of each eye. The SC was detected in 100.0% of the sections. The distribution of individual measurements of SC was highly variable. The mean values of SC size significantly differed among the different clock-face positions. The mean values of the area, perimeter, and diameter of SC in the 9:00 o’clock position were the lowest, and those at the 7:30 o’clock position were the highest (P < .05). There was no obvious association between intraocular pressure and SC size at any clock position. Although SC tends to open circumferentially in normal individuals, the distribution of individual measurements is highly variable. Morphological manifestation of SC measured by EDI-OCT is a useful way to evaluate the circumferential opening status of SC.