Iridotrabecular Contact Observed Using Anterior Segment Three-Dimensional OCT in Eyes With a Shallow Peripheral Anterior Chamber

Abstract

To evaluate the prevalence and range of iridotrabecular contact (ITC) in eyes with a shallow peripheral anterior chamber (AC) by using anterior segment swept-source optical coherence tomography (AS-SS-OCT) and to compare the results with those obtained with ultrasound biomicroscopy (UBM) and gonioscopy. Forty-three shallow peripheral AC eyes in 43 consecutive patients underwent gonioscopy. Cross-sectional images throughout the angle circumference (i.e., 360°) were obtained with AS-SS-OCT (SS-1000 noncontact, noninvasive three-dimensional imaging system) and those of the peripheral AC at the 3, 6, 9, and 12 o'clock positions were obtained with UBM (UD-1000). ITC evaluated with AS-SS-OCT included all gonioscopically identified peripheral anterior synechia (PAS) in the area. With AS-SS-OCT, at least one ITC was found in 40 (93.0%) and 42 (97.7%) of the 43 eyes under light and dark conditions, respectively, whereas with UBM, at least one ITC was found in 22 (51.1%) and 36 (83.7%) of the 43 eyes under light and dark conditions. The prevalence of ITC in eyes with AS-SS-OCT was significantly higher than that with UBM under light conditions, but not under dark conditions (P = 0.0001, 0.07, respectively, sign test). The PAS-positive eyes had a significantly greater ITC range than the PAS-negative eyes under light conditions (P = 0.006), but not under dark conditions (P = 0.08). AS-SS-OCT detected all PAS and the prevalence of ITC detected by AS-SS-OCT in narrow angle eyes was markedly higher than previously thought. A relationship between the ITC range under light conditions and future PAS formation was suggested.