Retinal angiomatous proliferation in age-related macular degeneration

Background: It is known that choroidal neovascularization (CNV) in age-rela ted macular degeneration (ARMD) may erode through the retinal pigment epith elium, infiltrate the neurosensory retina, and communicate with the retinal circulation in what has been referred to as a retinal-choroidal anastomosi s (RCA). This is extremely common in the end stage of disciform disease. In recent years, the reverse also seems to be possible, as angiomatous prolif eration originates from the retina and extends posteriorly into the subreti nal space, eventually communicating in some cases with choroidal new vessel s. This form of neovascular ARMD, termed retinal angiomatous proliferation (RAP) in this article, can be confused with CNV. Purpose: The purpose of this article is 1) to review the clinical and angio graphic characteristics of a series of patients with RAP and 2) to propose a theoretical sequence of events that accounts for the neovascularized proc ess. Methods: In this retrospective clinical and angiographic analysis, 143 eyes with RAP (108 patients) were reviewed and classified based on their vasoge nic nature and course. Clinical biomicroscopic examination, fluorescein ang iography, and indocyanine green angiography were used to evaluate patients. Results: The results of this series suggest that angiomatous proliferation within the retina is the first manifestation of the vasogenic process in th is form of neovascular ARMD. Dilated retinal vessels and pre-, intra-, and subretinal hemorrhages and exudate evolve, surrounding the angiomatous prol iferation as the process extends into the deep retina and subretinal space. One or more dilated compensatory retinal vessels perfuse and drain the neo vascularization, sometimes forming a retinal-retinal anastomosis. Fluoresce in angiography in these patients usually revealed indistinct staining simul ating occult CNV. Indocyanine green angiography was useful to make an accur ate diagnosis in most cases. It revealed a focal area of intense hyperfluor escence corresponding to the neovascularization ("hot spot") and other char acteristic findings. Based on understanding of the nature and progression o f the neovascularized process, patients with RAP were classified into three vasogenic stages. Stage I involved proliferation of intraretinal capillari es originating from the deep retinal complex (intraretinal neovascularizati on [IRN]). Stage II was determined by growth of the retinal vessels into th e subretinal space (subretinal neovascularization [SRN]). Stage III occurre d when CNV could clearly be determined clinically or angiographically. A va scularized pigment epithelial detachment and RCA were inconsistent features of this stage. Conclusions: Retinal angiomatous proliferation appears to be a distinct sub group of neovascular ARMD. It may present in one of three vasogenic stages: IRN, SRN, or GNV. Whereas ICG angiography is helpful in diagnosing RAP and in documenting the stage of the neovascularized process, it is frequently difficult to determine the precise nature and location of the new vessel fo rmation. It is important for clinicians to recognize the vasogenic potentia l and the associated manifestations of this peculiar form of neovascular AR MD so that a proper diagnosis can be made, and when possible, an appropriat e management administered.