Assessment of CNV activity with OCT-angiography.
Luis Arias, MD, PhD. Bellvitge University Hospital. Associate Professor. University of Barcelona.
Choroidal neovascularization (CNV) activity is usually assessed with SD-OCT or SS-OCT in clinical practice. Currently, OCT-angiography (OCT-A) allows for detection and monitoring of CNV without needing dye injection. Two well-defined patterns of CNV have been identified with OCT-A:
1)active CNV showing subretinal and/or intraretinal fluid on B-scans,
2)quiescent CNV without subretinal and/or intraretinal fluid on B-scans.
However, in patients with mild macular fluid and stable visual acuity it is difficult to determine whether the CNV is active or not. The similarity between the CNV appearance on OCT-A and a dead or a leafy tree can be helpful in some cases. Likewise, the density map and the blood flow distribution on the corresponding B-scan can assist for the assessment of the CNV activity. In addition, en face images can be helpful for mapping intraretinal cysts in retinal angiomatous proliferation lesions. Importantly, in patients with atrophy of the retinal pigment epithelium choroidal vessels should not be mixed up with CNV. It should be noted that some patients show CNV on OCT-A in the absence of macular fluid at any time. Therefore, the term “neovascular” appears to be more convenient than “wet or exudative” to name the disease. At present, some software programs used in other medical specialties are available to quantify the CNV features detected on OCT-A. Future refinements in these programs will provide us more accuracy to determine CNV activity secondary to age-related macular degeneration and other retinal disorders.