Static Ocular Biometrics Predict Primary Angle Closure Progression

Static ocular biometrics, measured in both light and dark conditions, may best predict progression from primary angle closure suspect (PACS) to primary angle closure (PAC), according to research published in the American Journal of Ophthalmology.

Researchers conducted a retrospective cohort study using prospective data from a single-center randomized controlled trial of patients with bilateral PACS. In the trial, one eye per participant underwent random assignment to treatment, while the other eye served as a control eye. All study participants underwent anterior segment optical coherence tomography (AS-OCT) in dark and light conditions.

The researchers included data from the untreated, control eyes (n=861; mean age, 58.68 years; 76.7% women) to assess and compare dynamic (light minus dark measurements) and static ocular biometrics (angle, iris, lens, and anterior chamber parameters) and determine risk factors for angle closure progression. The main study endpoint was PAC development, which the team defined as intraocular pressure (IOP) higher than 24 mm Hg at 2 separate visits, 1 or more clock hours of peripheral anterior synechiae, or an acute angle closure attack.

A total of 36 (4.2%) participants progressed to PAC (mean age, 60.08±5.76 years; 83% men), the report shows. A univariable analysis comparing non progressors vs progressors demonstrated that progression was associated with trabecular iris space area bound by an angle opening distance 500 µm anterior to the scleral spur (TISA500) in light (0.083 vs 0.059 mm²; P <.001) and dark conditions (0.055 vs 0.033 mm²; P <.001). However, dynamic change parameters were not associated with progression. 

Multivariable analysis revealed that older age (hazard ratio [HR], 1.09 per 1 year; 95% CI, 1.02-1.17; P =.02), higher IOP (HR, 1.13 per 1 mm Hg; 95% CI, 1.01-1.26; P =.04), and smaller TISA500 in light conditions (HR, 1.28 per 0.01 mm²; 95% CI, 1.11-1.47; P =.001) were associated with a greater PAC progression risk. In a second analysis, replacing TISA500 in the light with TISA500 in the dark yielded a similar result (HR, 1.28; 95% CI, 1.09-1.49; P=.002). 

“These findings raise questions about the clinical convention of solely assessing angles in the dark and ideal lighting conditions to risk stratify patients with PACS for more severe disease,” the study authors explain. “Our findings further suggest that biometrics measured in the light may provide additional information about angle closure progression compared to biometrics measured in the dark alone. Due to the angle-widening effect of pupillary constriction, imaging PACS eyes in the light produced a more even distribution of angle width measurements than in the dark.”

Limitations of the study included the relatively small sample of individuals who progressed to PAC and an ethnically homogenous cohort, which may limit the globalization of these findings.