OCT enhances neovascular subtype detection in AMD

By Lucy Piper, Senior medwireNews Reporter

Researchers recommend the inclusion of optical coherence tomography (OCT) anatomic classification with fluorescein angiography (FA) grading to identify initial neovascular lesion subtypes in newly diagnosed age-related macular degeneration.

Advancements in imaging have resulted in the development of high-definition spectral-domain OCT, which offers additional resolution to FA and can better localise the neovascular tissue according to Gass’s anatomic terminology, providing a more refined classification to the FA-based grading guidelines of the Macular Photocoagulation Study.

The introduction of OCT enabled the classification of neovascularisation to be extended from the initial “classic” or well-defined choroidal neovascularisation (CNV) and “occult” or poorly defined CNV, to include type 3 neovascularisation, also known as retinal angiomatous proliferation (RAP).

Researchers K Bailey Freund (Vitreous, Retina, Macula Consultants of New York, USA) and colleagues compared the ability of the two classification systems to identify lesion subtypes in 232 (266 eyes) patients with treatment naïve neovascular AMD in at least one eye treated with anti-vascular endothelial growth factor therapy. The patients had a mean age of 86.3 years.

According to FA alone, 49.6% of eyes were classified as occult CNV, 12.0% as classic CNV, 28.6% as RAP and 9.8% as mixed CNV.

With FA and OCT, 39.9% of eyes were classified as type 1 (subretinal pigment epithelium) neovascularisation, 9.0% as type 2 (subretinal), 34.2% as type 3 (intraretinal) and 16.9% as mixed neovascularisation.

There was good agreement between the two classification systems. The only discrepancies were a significant increase in type 3 and mixed neovascularisation lesions and a decrease in the type 1 subtype when OCT was used in addition to FA.

“As expected, OCT was useful in identifying the neovascular vessels and cystic spaces within the retina but was less helpful in assessing changes beneath the pigment epithelium,” the researchers comment in the American Journal of Ophthalmology.

“The anatomic classification system offers a more reliable method for identifying important baseline information that should allow for a better understanding of pathogenesis and risk factors for the development of specific neovascular lesions”, they say.

This, in turn, could “allow for more individualized therapy and would identify those eyes more susceptible to certain complications, including geographic atrophy”, the team concludes.

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