Evolution of CNV imaging

OCT invaluable in tracking choroidal neovascularisation

Dermot McGrath

Posted: Wednesday, May 1, 2019

Karen B. Schaal MD, FEBO

Optical coherence tomography is an extremely valuable imaging modality that complements traditional fluorescein angiography (FA) in the diagnosis and management of choroidal neovascularisation (CNV) in age-related macular degeneration (AMD), according to Karen B. Schaal MD, FEBO.

“Spectral domain OCT (SD-OCT) and OCT angiography can help us to make the right diagnosis at an early stage in the disease process and to be able to identify the tell-tale signs of CNV activity as well as differentiate different lesion types, which will help determine the most appropriate course of treatment,” she said speaking at the 9th Euretina Winter Meeting in Prague.

Dr Schaal, University Hospital of Bern and Vista Diagnostics Zürich, said that OCT greatly facilitates understanding of the differences between classic and occult lesion types, retinal angiomatous proliferation (RAP) and disciform scars in the natural course of the disease and to gauge the response to anti-vascular endothelial growth factor (VEGF) drugs.

SD-OCT is also very useful to help differentiate outer retinal tubulation (ORT), intraretinal fluid (IRF) or so-called (pseudo)cysts, said Dr Schaal.

“It is important to be able to tell the difference as ORT features are not a sign of exudation and do not require anti-VEGF treatment. A (pseudo)cyst does not have an external limiting membrane (ELM) and it is usually located above the outer nuclear layer, whereas ORT always has an ELM, is located in the outer nuclear layer and has a distinctive hyper-reflective band,” she said.

The importance of identifying different lesion types has become more apparent in recent years, noted Dr Schaal.

“In the early days of anti-VEGF treatment this didn’t matter so much. We usually just looked for signs of lesion activity and treated the patient on that basis. Now, with years of experience of anti-VEGF therapies we know that different lesion types behave differently and require different treatment strategies,” she said.

Recent studies have shown that combined FA/OCT grading is capable of identifying a higher frequency of type 3 RAP lesions and a lower incidence of type 2 classic lesions than found previously in the scientific literature. This is significant because type 3 lesions typically follow a more severe disease course compared to type 1 and 2 lesions, she explained.

“We can usually expect a good response of type 3 lesions to anti-VEGF treatment if diagnosed early with a good visual prognosis. The patients in general are older than the average AMD age and they carry a high risk for atrophy, almost always associated with subretinal drusenoid deposits. It is a bilateral disease and it also carries a higher risk for cardiovascular events,” she concluded.

Karen B. Schaal: