This paper describes the role of anterior segment imaging in angle closure diagnosis and management, and explores the possible advantages of this approach over the current standard of gonioscopy.
Study design
This review summarizes the current literature on the use of anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) to assess the anterior chamber angle in patients with primary angle closure disease.
Outcomes
With gonioscopy as a reference for narrow angle detection, AS-OCT has a diagnostic sensitivity of 64% to 100% and a specificity of 55% to 100%, depending on the study population and narrow angle cutoffs. Short- and long-term reproducibility of AS-OCT measurements was excellent.
Eyes with certain imaging characteristics had a higher risk of angle closure, including those with higher iris curvature, larger iris area, thicker iris, higher lens vault, more anterior relative lens position, thicker lens, smaller anterior chamber width and lower anterior chamber volume. Repeat imaging after laser peripheral iridotomy revealed that lower iris thickness tracked with a greater change in post-laser iris curvature. In addition, a lower baseline angle opening distance or trabecular iris space area tracked with a greater post-laser widening.
Limitations
Although gonioscopy is typically regarded as the gold standard for angle assessment, studies have shown that too much light or inadvertent compression could underestimate the risk of angle closure, and there is poor inter- and intraobserver reproducibility. While anterior segment imaging is more reproducible than gonioscopy, there is little consensus on the most important parameters for angle closure risk or the most appropriate cutoffs.
Clinical significance
Anterior segment imaging provides a useful adjunct technique for evaluating and monitoring primary angle closure. This clinical video highlights how AS-OCT videos can be used in clinical practice.
Technological improvements are generating a tremendous amount of data, which can help ophthalmologists better classify narrow angle etiology (e.g., pupillary block, plateau iris, peripheral iris crowding or lens-related). These advances may also help identify patients who might benefit from laser iridotomy and provide a reproducible way to monitor these individuals. However, gonioscopy continues to provide valuable information about the dynamic appearance of the anterior chamber angle, the pigmentation of the meshwork and the presence of peripheral anterior synechiae or neovascularization.