Confocal microscopy of telangiectatic capillaries (TelCaps) and other features of microvascular remodeling following branch retinal vein occlusion.

Branch retinal vein occlusion (BRVO) is a frequent retinal vascular disease that may cause extensive microvascular remodeling leading to severe visual impairment. Little is known regarding the histology of non-neovascular microvascular remodeling. Here, we examined by confocal microscopy the structure of retinal microvessels of a donor eye with longstanding BRVO. The post-mortem retina of a 91-year-old woman that had superotemporal BRVO for 2 years was examined by confocal microscopy after anti-collagen IV (collIV), alpha-smooth muscle cell (αSMA), and anti-von Willebrand factor (vWf) immunolabeling. In the retinal quadrant affected by BRVO, extensive vascular remodeling affected all vessels, from arterioles to venules, including the foveal avascular zone. Most affected vessels were either irregularly dilated or, on the opposite, reduced to micrometric-size CollIV positive, vWf negative, nuclear-staining negative strings. Telangiectatic capillaries of various sizes and shapes were seen, the largest one (233 μm) being located in the parafoveal area. Some telangiectatic capillaries had a thick, multilayered vWf- and CollIV-positive wall, that often occluded the lumen. Other features included double-channeled arterioles. The majority of microvascular abnormalities were devoid of nuclear staining, suggesting extensive loss of endothelial cells. We describe the spectrum of microvascular abnormalities upstream of a longstanding BRVO. This spectrum comprises a large parafoveal telangiectatic capillary corresponding to what has been previously clinically defined as TelCap. The absence of intraluminal nuclear staining in the majority of abnormal vessels raises the hypothesis that the loss of endothelial cells plays a crucial role in the development of the different manifestations of capillary remodeling. The presence of vWF in de-endothelialized vessels suggests deposition of plasma, hence that they may remain perfused. Our work may help to understand the clinical imaging features of TelCaps.