Impact and Consequences of Verteporfin Photodynamic Therapy on Choroidal Neovascular Membranes

Abstract

Abstract: : Purpose:To evaluate the impact of verteporfin photodynamic therapy (PDT) on the expression and distribution of vascular endothelial growth factor (VEGF) in association with vascularization and proliferation activity in choroidal neovascular membranes (CNV) secondary to age related macular degeneration (AMD). Methods: Retrospective review of an interventional case series of fifty patients who underwent removal of CNV (n=50) secondary to AMD. Twenty of these patients were treated with PDT 3 to 655 days before surgery. CNV were stained for CD 34, CD 105(endoglin), Ki–67, Cytokeratin 18 and VEGF. Thirty CNV secondary to AMD without previous treatment were used as control. Immunohistological results were correlated with clinical findings and fluorescein angiography. Results:Specimens without pre–treatment disclosed different degrees of vascularization, proliferative activity and VEGF expression by different cells. Specimens that had been treated by PDT three days previously showed mostly occluded vessels, damaged endothelial cells and low proliferative activity. In contrast, specimens excised at later time points after PDT were highly vascularized and proliferating. This chronology was associated with an impressive VEGF immunoreactivity unique to retina pigment epithelial cells shortly after PDT that shifts also to endothelial and stromal cells at later time points. Conclusions: Verteporfin PDT induces a selective vascular damage in CNV. The effectiveness and selectivity of this treatment, however, seems to be jeopardized by a rebound neoangiogenesis initiated by an enhanced VEGF expression in RPE cells. The cause for this effect may be based on the ischemic insult and/or the increase of free radicals induced by PDT.

Keywords: photodynamic therapy • choroid: neovascularization • age-related macular degeneration