Retinal Angiomatous Proliferation
Dr. Swati Mishra, Dr. Sarang Lambat, Dr. Vinay Nangia
Suraj Eye Institute, Nagpur, India
Introduction:
In age-related macular degeneration (ARMD), choroidal neovascularization (CNV) may proliferate through the retinal pigment epithelium (RPE), infiltrate the retina, and communicate axonally and freely with the retinal circulation, forming a retino–choroidal anastomosis (RCA). This distinct form of neovascular ARMD, which is associated with proliferation of retinal capillaries and an associated contiguous telangiectatic response, is known as retinal angiomatous proliferation (RAP). Fluorescein angiography (FA) in patients with RAP shows intra- and sub-retinal vessels and the underlying detachment usually produces an indistinct continuous zone of staining within and beneath the retina, simulating ill defined or so-called occult CNV. Indocyanine green (ICG) angiography is helpful in making an accurate diagnosis of RAP, as it identifies a focal area of intense hyperfluorescence (“hot spot”) corresponding to the neovascularization.(1)
Case Report :
A male, 84 years of age, known case of exudative ARMD, has been on 4-5 anti VEGF injections every year since past 5 years. His visual acuity was counting finger (CF) 3m in right eye (RE) and 6/9 in left eye (LE). He was pseudophakic in both eyes (BE) with a pressure of 18 mm Hg in BE. RE fundus examination showed a vertical cup disc ratio of 0.5, large PED at macula with retino- retinal and retino-choroidal anastomosis.(Fig1) LE fundus evaluation showed a vertical cup disc ratio of 0.6 and intermediate ARMD. OCT in RE showed macular edema with sub-retinal fluid and sub-RPE fluid. (Fig 2) There was no significant improvement of vision with anti VEGF therapy so he was given direct thermal photocoagulation along with the intravitreal injection. Post-therapy his vision improved to 6/24 and OCT showed contour of macula returning to normal with no sub retinal or sub RPE fluid.
Discussion:
A retinal choroidal anastomosis is known to occur most prominently in neovascular ARMD and in several different types of maculopathies, including infections with organisms such as toxoplasmosis, photocoagulation, trauma, post radiation, vaso-proliferative chorioretinal tumours, idiopathic perifoveal telangiectasia.(1) The pathogenesis of RAP is similar to ARMD which involves RPE dysfunction, bruch membrane changes and reduction in choroidal blood flow resulting in hypoxia of the outer retinal layers leading to release of VEGF (2) The natural history of untreated RAP lesions appears to be poor due to progression to different stages with frequent development of disciform scarring. (3)
Stages of progression of RAP are categorised by the extent of retinal and choroidal involvement:-
Stage I- Intra-retinal neovascularization
Stage II- Sub-retinal neovascularization
Stage III- Choroidal neovascularization (4)
Direct laser photocoagulation of the vascular lesion, laser photocoagulation of the feeder retinal arteriole, scatter grid like photocoagulation, photodynamic therapy and transpupillary thermotherapy are the options which have been describe in literature for the treatment of RAP(2). Since in this case the vascular abnormalities were visualised very well clinically we could achieve satisfactory closure of the lesion with direct laser photocoagulation. This resulted in achieving better long-term visual outcome. The patient is still maintaining 6/24 BCVA after 35 injections since a period of almost 11 years.