Identification of peripheral anterior synechia with anterior segment optical coherence tomography

Purpose To generate a model that evaluates the presence and extent of peripheral anterior synechia (PAS) based on anterior segment optical coherence tomography (AS-OCT). Methods The extent of PAS involvement in the eyes of patients with angle closure was assessed by indentation gonioscopy, and the part of non-PAS and PAS were assigned into two groups (NPAS and PAS). Anterior chamber angles were then imaged by AS-OCT with light-emitting diode (LED) irradiation directly into the pupils, leading to pupillary constriction and increasing anterior chamber angle width. Parameters including the angle opening distance at 750 μm anterior to the scleral spur (AOD750) and trabecular-iris space area at 750 μm anterior to the scleral spur (TISA750) were then obtained. The differences before and after LED irradiation of AOD750 and TISA750 were calculated and used to generate a PAS model based on binary logistic regression. Validation data were then tested. Results A total of 258 AS-OCT images in 14 eyes were assigned to the modeling data, and 120 were assigned to the validation data. There were no differences in AOD750 and TISA750 in the dark between NPAS and PAS ( P AOD750 = 0.258, P TISA750 = 0.486), whereas after LED light exposure, TISA750 light was larger in NPAS than in PAS ( P = 0.047). The light–dark differences of both parameters showed significant differences between the two groups ( P AOD750dif = 0.019, P TISA750dif