Study Points to Importance of Monitoring Nonexudative CNV with OCTA
By David Huang MD, PhD
Because OCT angiography (OCTA) detects choroidal neovascularization (CNV) with high sensitivity and specificity and is noninvasive and fast, it is introducing us to better ways of diagnosing and monitoring patients with age-related macular degeneration (AMD). Of significant interest is the ability of OCTA to detect a relatively new subclinical entity — nonexudative CNV.1 While it is possible to identify nonexudative CNV with indocyanine green angiography (ICGA), the time, expense and risk associated with ICGA make it impractical for frequent assessment. OCTA eliminates these barriers, making it easy to keep close tabs on nonexudative CNV.
A prospective observational study conducted by Steven Bailey, MD, and others at the Casey Eye Institute2 suggests that eyes with intermediate AMD should be monitored routinely with OCTA, especially if they have exudation in the fellow eye. We used OCTA to evaluate 63 eyes with intermediate AMD and exudation in the fellow eye. Ten eyes were found to have nonexudative CNV either on the initial scan or a subsequent scan during 24 or more months of follow-up. Of those 10 eyes, eight (80%) progressed to exudation, which occurred within 10 months. In most of the eyes, exudation developed within 6 months. Comparing the rate of occurrence of exudation between the eyes with and without nonexudative CNV, the Cox hazard ratio was 18. Furthermore, the change from nonexudative CNV to exudative CNV was preceded by rapid growth in lesion size as measured by OCTA (Figure 1). Nonexudative CNV did not appear in 53 of the eyes during the study. Those eyes had a lower risk of developing exudation.
Our study suggests that nonexudative CNV is a precursor to exudation and should be monitored closely with OCTA. A logical next step would be randomized trials to evaluate whether prophylactic treatment of nonexudative CNV could prevent exudation and save vision in the long term at reasonable costs. The growth rate of nonexudative lesions as measured by OCTA could be used as the guide for starting and stopping anti-VEGF treatment and should be considered in the design of such trials.
Figure 1. In eyes with intermediate AMD, particularly when exudative CNV is present in the fellow eye, nonexudative CNV is a precursor to exudation and should be monitored with OCTA.
1. Palejwala NV, Jia Y, Gao SS, et al. Detection of nonexudative choroidal neovascularization in age-related macular degeneration with optical coherence tomography angiography. Retina. 2015;35(11):2204-2211.
2. Huang D. Nonexudative CNV identified by OCTA is a precursor to exudation. Presentation at the American Society of Retina Specialists Annual Meeting, July 23, 2018, Vancouver, British Columbia, Canada.
Dr. Huang, a co-inventor of optical coherence tomography, is the Peterson Professor of Ophthalmology and a professor of biomedical engineering at the Oregon Health & Science University in Portland, where he also leads the Center for Ophthalmic Optics and Lasers (COOL Lab).