Histology of type 3 macular neovascularization and microvascular anomalies in treated age-related macular degeneration: a case study

Objective/Purpose To investigate intraretinal neovascularization and microvascular anomalies by correlating in vivo multimodal imaging with corresponding ex vivo histology in a single patient. Design A case study comprising clinical imaging from a community-based practice, and histologic analysis at a university-based research laboratory (clinicopathologic correlation). Participants A white woman in her 90’s treated with numerous intravitreal anti-vascular endothelial growth factor (VEGF) injections for bilateral type 3 macular neovascularization (MNV) secondary to age-related macular degeneration (AMD). Intervention(s)/ Methods Clinical imaging comprised serial infrared reflectance, eye-tracked spectral-domain optical coherence tomography (OCT), OCT angiography, and fluorescein angiography. Eye tracking, applied to the two preserved donor eyes, enabled correlation of clinical imaging signatures with high-resolution histology and transmission electron microscopy. Main Outcome(s) and Measure(s) Histologic/ ultrastructural descriptions and diameters of vessels seen in clinical imaging. Results Six vascular lesions were histologically confirmed (type 3 MNV, n=3; deep retinal age-related microvascular anomalies (DRAMA), n=3). Pyramidal (n=2) or tangled (n=1) morphologies of type 3 MNV originated at the deep capillary plexus (DCP) and extended posteriorly to approach without penetrating persistent basal laminar deposit. They did not enter the sub-retinal pigment epithelium (RPE)-basal laminar space or cross Bruch’s membrane. Choroidal contributions were not found. The neovascular complexes included pericytes and non-fenestrated endothelial cells, within a collagenous sheath covered by dysmorphic RPE cells. DRAMA lesions extended posteriorly from the DCP into the Henle fiber and the outer nuclear layers, without evidence of atrophy, exudation, or anti-VEGF responsiveness. Two DRAMA lacked collagenous sheaths. External and internal diameters of type 3 MNV and DRAMA vessels were larger than comparison vessels in the index eyes and in aged normal and intermediate AMD eyes. Conclusions Type 3 MNV vessels reflect specializations of source capillaries and persist during anti-VEGF therapy. The collagenous sheath of type 3 MNV lesions may provide structural stabilization. If so, vascular characteristics may be useful in disease monitoring in addition to fluid and flow signal detection. Further investigation with longitudinal imaging before exudation onset will help determine if DRAMA are part of the type 3 MNV progression sequence.