Identifying primary angle-closure diseases (PACD) sooner rather than later, especially primary angle closure (PAC) and primary angle-closure glaucoma (PACG), may help prevent permanent vision loss. A common diagnostic approach to detecting these conditions is using swept-source OCT (SS-OCT) of the anterior segment because of its ability to image 360 degrees of the relevant ocular structures and obtain over 100 scans in seconds. This study found that SS-OCT excelled at distinguishing between healthy and PACG eyes and was also able to moderately distinguish between PAC/PACG and primary angle-closure suspect eyes.

The study analyzed a total of 2,928 SS-OCT images from 366 eyes of 260 Chinese patients and used 1,176 images from 147 eyes of 143 patients as a validation set. To evaluate discriminability, researchers calculated the area under the receiving operating characteristics curve (AUC), a measure of the prognostic ability of a model. Based on their results, they found that anterior chamber depth (ACD), even when measured using more available modalities than SS-OCT, could diagnose early PACD. 

“For distinguishing PACD from control, average ACD had the highest AUC of 0.94,” the researchers wrote in their paper. “With a cut-off of 2.2mm for average ACD, the sensitivity and specificity were 90.2% and 85.2% in the training set. For distinguishing PACS from PAC/PACG, a multivariate model had an AUC of 0.83, with sensitivity and specificity of 82.0% and 62.8% in the training set,” they wrote.

Patients with PAC and PACG have a three times greater risk of blindness than those with primary open-angle glaucoma, not to mention the rising glaucoma rates expected to reach nearly 112 million by 2040. Early diagnosis of PACD is the most effective way to preserve vision, and luckily, it does not require advanced imaging such as SS-OCT to be detected. Measuring ACD in your patients may be an excellent diagnostic tool for those at risk for PACD. 

“As ACD may be obtained using other more readily available modalities, this has implications for diagnosis of PACD with objective cutoff values, which is particularly useful in settings with limited ophthalmic care,” the authors concluded.

Ma P, Wu Y, Oatts J, et al. Evaluation of the diagnostic performance of swept-source anterior segment optical coherence tomography in primary angle-closure disease. Am J of Ophthalmol. June 25, 2021. Epub ahead of print.