In some eyes, type 1 lesions develop a type 3 component and other cases in which type 3 lesions originate over areas of pre-existing type 1 NV. These lesions would be best classified as mixed type 1 and 3 NV, he noted.
So, this begs the question regarding why so much attention is focused on type 3 NV.
“Type 3 NV occurs almost exclusively in AMD and is far more common than previously recognized,” Dr. Freund said. “In a consecutive series of newly diagnosed treatment-naïve AMD eyes, Jung et al. identified type 3 NV as the predominant lesion component in 34.2% of their cases.”
When recognized early, type 3 NV responds well to intravitreal anti-vascular endothelial growth factor (VEGF) therapy, but over the long term, visual outcomes can be poor since these eyes are at high risk for bilateral involvement and macular atrophy.
The origin of type 3 NV still is unclear. However, researchers who evaluated submacular tissue obtained intraoperatively and intact post-mortem eyes have pointed to retinal and not choroidal sources because of the absence of vascular connections through defects in Bruch’s membrane.