Histopathological Findings of Recurrent Choroidal Neovascular Membrane Treated With Photodynamic Therapy

Abstract

Purpose:: In recurrent choroidal neovascular membrane (CNV) after photodynamic therapy (PDT), revascularization is caused by both recanalisation and angiogenesis. Recent studies dealing with tumor vessels reported that recanalisation is illustrated histologically by reformation of novel lamina within previously occluded channels and duplication of vascular basement membranes (VBM). To reveal whether recurrent CNV after PDT shows these histological changes, we analyzed surgically excised CNV by electron microscopy.

Methods:: We studied two surgically excised CNVs due to age related macular degeneration (AMD). One CNV, which is from 81-year-old man, is after three series of PDTs and subsequent one-time transpupillary thermo therapy (TTT). The other CNV, which is from 63-year-old man, is previously untreated. In both cases, we performed vitrectomy and then excised the CNV. The excised CNVs were fixed in 4% glutaraldehyde and postfixed with 1% osumium tetroxide. The CNVs were embedded in Epon-araldite resin and polymerized. We then cut serial ultrathin sections and stained them with an aqueous solution of uranyl acetate and lead citrate. We observed the specimens with transmission electron microscope.

Results:: The recurrent CNV after PDT and TTT showed two to five layers of VBM and unusual arrangement of vascular endothelial cell, pericyte and VBM. In contrast, previously untreated CNV showed normal vascular structure including monolayer of VBM.

Conclusions:: The histopathological characteristics of recurrent CNV after PDT are multilayered VBM and unusual vascular structure, which represent recanalisation of CNV. These results indicate the importance of recanalisation as a causal factor of revascularization of CNV.

Keywords: neovascularization