Anterior segment parameters measured by ultrasound biomicroscopy in the subtypes of angle‐closure

Purpose To compare anterior segment parameters in primary angle closure suspect (PACS), primary angle closure (PAC), and primary angle closure glaucoma (PACG) using ultrasound biomicroscopy (UBM P60, Paradigm Inc, Utah, USA). Methods 59 eyes of 59 patients with PACS, 41 eyes of 41 patients with PAC, and 51 eyes of 51 patients with PACG were investigated. Definitions of PACS, PAC, and PACG were based on the recommendation from the International Society for Geographic and Epidemiological Ophthalmology. In each participant, slit lamp examination, funduscopy, gonioscopy, Goldmann applanation tonometry and UBM were performed. Anterior segment parameters such as anterior chamber depth (ACD), anterior chamber width (ACW), lens vault (LV), angle opening distance 500 (AOD500), trabecular meshwork‐ciliary process distance (TCPD), iris thickness (IT) and iris zonular distance (IZD) were evaluated. Results AOD500 were significantly different among the angle‐closure subtypes in nasal, inferior, and temporal quadrants (PACS > PACG > PAC; p < 0.05). TCPD were significantly different among the subtypes in all quadrants (PACG > PACS > PAC; p < 0.05). ACD were significantly different among the subtypes (PACG > PACS > PAC; p < 0.05). ACW, LV, IT and IZD were not significantly different among the subtypes (p > 0.05). Conclusions AOD500, TCPD, and ACD were the smallest in PAC, and ACW, LV, IT, and IZD were similar among the angle‐closure subtypes. There may be a consequence in the development of angle‐closure from mild to severe damages (from PACS to PAC to PACG) in terms of intraocular pressure, angle status, and optic nerve head status. However, our results suggested that such consequence may not exist in anterior segment morphology measured by UBM.