Iris Trabecular Contact Shows Good Diagnostic Ability for Angle Closure Glaucoma

Assessing iris trabecular contact using anterior segment-optical coherence tomography (AS-OCT) may be a more precise method of identifying primary angle closure and primary angle closure glaucoma (PAC and PACG, respectively) compared with gonioscopy, according to a study published in Ophthalmology.

Researchers included 119 participants with gonioscopic open-angle(mean age, 60.8 years; 72 women) and 170 patients with gonioscopic angle closure (mean age, 63.5 years; 122 women; 94 PAC suspects; 76 individuals with PAC/PACG) in the multicenter, prospective study. All participants underwent AS-OCT imaging and dark-room gonioscopy during the same visit. The team obtained 36 angle opening distance (AOD500) and trabecular iris space area (TISA500) measurements (every 10° for 360°) and defined iris trabecular contact when either of these values were 0. The AOD500 measurement included the perpendicular distance from the posterior corneoscleral junction at 500 µm anterior to the scleral spur to the anterior iris surface, while the TISA500 included the area bounded anteriorly by the AOD500, according to the report.

Iris trabecular contact most frequently occurred at the superonasal sector at 110° (182 eyes) and least frequently in the inferotemporal sector at 340° (56 eyes). Overall, AS-OCT did not reveal iris trabecular contact in 15.3% to 17.6% of eyes, indicating a sensitivity between 82.4% and 84.7% for detecting gonioscopic angle closure. 

The extent of iris trabecular contact, not cumulative gonioscopy score, was associated with the odds of PAC or PACG in eyes with gonioscopic angle-closure, the report shows. The odds of PAC or PACG increased by 5% for every 10° increase in iris trabecular contact (OR, 1.051, 95% CI, 1.022-1.080 for AOD500=0 mm; OR, 1.049, 95% CI, 1.022-1.078 for TISA500=0 mm²).

No association was noted between axial length and anterior chamber depth and PAC or PACG in eyes with gonioscopic angle-closure (P ≥.574).

“Gonioscopic angle-closure may not always represent anatomic angle-closure; 15.3% to 17.6% of eyes with gonioscopic angle-closure had no evidence of [iris trabecular contact] in AS-OCT, and only 31.8% to 35.3% had ITC500 for 180,” according to the researchers. “More important, the extent of [iris trabecular contact] could be more clinically relevant than gonioscopy grading to the evaluation of PAC/PACG.”

Consecutively recruiting participants from eye clinics could limit the generalizability of study findings due to higher degrees of angle closure and iris trabecular contact extents compared with population-based cohorts, and is an acknowledged limitation to the research.