Angle Closure Linked With Narrower Structure at Iris Root

Patients with primary angle closure disease (PACD) have narrower anterior segment angle structures at 250 μm from the scleral spur, compared with individuals without PACD who have shallow anterior chamber depth (ACD), according to a study published in the Journal of Glaucoma. The research employed swept-source optical coherence tomography (SS-OCT) measurements.

The researchers used swept-source optical coherence tomography (SS-OCT) to examine anterior segment structures in normal eyes of control participants whose ACD was shallow on slit-lamp examination but did not meet the diagnostic criteria of PACD, and compared them with those of patients with PACD and similar ACD.

Patients were recruited from a single glaucoma clinic. All participants underwent ophthalmic and SS-OCT examination. Eyes with PACD and control eyes were matched (1:1) for ACD at 0 degree of scan. Angle area was assessed by angle parameters, including angle recess area and trabecular iris space area, measured at 250 μm, 500 μm, and 750 μm along axes ranging from 0 to 315 degrees. The investigators constructed a generalized linear model that accounted for inter-eye correlation to compare differences between the groups for intraocular pressure and SS-OCT parameters. 

A total of 80 eyes of 63 participants (60.3% women and 39.7% men) were included in the study. Of those, 40 eyes from 29 patients had PACD (mean age 65.9 ± 14.0 years) and 40 eyes from 34 control participants (mean age 58.8 ± 12.9 years; P =.06). The PACD PACD group had a significantly higher intraocular pressure (18.4 vs 14.0 mm Hg, P =.005) than the control group. Of the PACD group, PACD was the primary angle closure suspect in 16 eyes (40.0%), primary angle closure in 11 eyes (27.5%), and primary angle closure glaucoma in 13 eyes (32.5%).

Angle parameters measured at 250 μm along axes of 90, 135, 225, and 315 degrees were significantly smaller in the PACD group than in the control group (Bonferroni adjusted P <.05). Nearly all angle parameters at 500 μm and 750 μm, volume parameters, and anterior chamber parameters were similar between the groups.

“In summary, in this cross-sectional study, we have found that compared with ACD-matched controls, patients with PACD have narrower structure at the very root of iris measured 250 μm from [the scleral spur], especially in the oblique and vertical axis. The parameters indicating the angle area, such as [trabecular-iris space area] and [angle recess area], seem to match better with gonioscopic examinations,” investigators report.

Limitations of the study included inability to infer causality, potential human errors in manual labeling of the scleral spur and angle recess, inability to compare between PACD subgroups due to small sample sizes, potential inherent sampling bias, and an all Chinese patient population at a single center.

Reference

Xie Q, Ma P, Patlidanon J, et al. Anterior segment OCT in primary angle closure disease compared with normal subjects with similar shallow anterior chamber. J Glaucoma. 2022;31(2):84-90. doi:10.1097/IJG.0000000000001915