Type 3 neovascularization - The expanded spectrum of retinal angiomatous proliferation

Background: Retinal angiomatous proliferation (RAP) is a distinct form of neovascularization in patients with age-related macular degeneration. Lacking definitive sequential histopathologic evidence of its intraretinal versus choroidal origin, the clinical observations of early stages of RAP lesions may provide clues to help further expand our understanding of this entity. Methods: Five eyes of four patients with early Stage 1 RAP were examined. Fundus photography, fluorescein and indocyanine green angiography as well as time-domain and spectral-domain optical coherence tomography were performed. Images were assessed to determine the characteristics of neovascularization in early stage RAP lesions and the response of the lesions to treatment or observation. Results: The analysis of the selected cases suggests a choroidal origin of the neovascular complex with the early formation of a retinal choroidal anastomosis without evidence of underlying occult Type 1 neovascularization. Three eyes responded to a single treatment with intravitreal ranibizumab (0.5 mg) and 2 eyes (1 patient) resolved spontaneously without treatment. Conclusion: The neovascularization in RAP may originate not only from deep retinal capillaries but also from the choroid. We therefore propose the more descriptive term "Type 3 neovascularization" for this entity to emphasize the intraretinal location of the vascular complex and distinguish this type from the two types of neovascularization previously described by J. Donald Gass in his classic text.