Morphology of early choroidal neovascularisation in age-related macular degeneration: correlation with activity

The purpose of this study was to describe the morphology of early choroidal neovascularisation (CNV) and compare the findings in two patients, in the first of whom the vessels appeared inactive and in the second progressive. Changes common to both included a diffuse deposition of membrane coils external to the basement membrane (BsM) of the retinal pigment epithelium (RPE), and macrophages and foreign body giant cells beneath thinned segments of Bruch's membrane (BrM). In the first patient small activated vessels surrounded by enlarged pericytes were found in the choroid beneath these areas and pursued a convoluted course, bulging into or through BrM, but without spreading in the sub-RPE space. This choroidal phase of CNV may be common and unrecognised. In the second patient there was spread of CNV in the sub-RPE space with extravasation of red cells and fibrin. The tips leaking fibrin were covered by a thick BsM-like material and naked endothelial cells were not seen. Pericytes were absent here but were observed at the non-leaking edge. The difference in activity of CNV in the two patients appeared to correlate with the quantity of membranous debris present.