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M.H. Criswell, T.A. Ciulla, L. Lowseth, R.P. Danis, D. Carson; Chorioretinal Anastomoses Remain Viable after Photodynamic Therapy (PDT) in Primate Models of Choroidal Neovascularization (CNV) . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3948.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Chorioretinal anastomoses (CRAs) occur in exudative age-related macular degeneration (AMD), and represent a serious clinical feature that reportedly does not respond well to photocoagulative therapy. CRAs also have been demonstrated in various animal CNV models. Here we examined the effect of PDT on CRAs in 2 primate CNV laser-trauma models. Methods: CNV’s were produced in 20 eyes from squirrel (Saimiri sciureus) and cynomolgus (Macaca fascicularis) monkeys following placement of laser photocoagulation sites as per previous protocols (Ciulla, et al., ARVO 2002; Ryan, SJ, Arch Ophthalmol. 1982, 100:1804). CNV, which developed in approximately 30-40% of photocoagulative sites in both species, was selectively treated in squirrel monkeys with PDT using a novel photosensitizer and in cynomolgus monkeys with the Alcon photosensitizer, motexafin lutetium (Pharmacyclics, Inc.), according to specific infusion and light treatment parameters for each agent. CRAs were identified during cross-sectional examinations of tissues (6 µm thickness) with light microscopy. Results: In both primate species, histologically distinguishable CRAs were found in approximately one-half of the photocoagulation sites that developed infiltrative CNV. Typically a vessel, emerging from the distal choroidal neovascular membrane, continued radially or at a slightly oblique orientation through the retina and formed a proximal connection with a retinal vessel. Following PDT, closure of vessels within the CNV membrane was reliably achieved, whereas retinal vessels remained open. Unexpectedly, CRAs appeared unaffected by PDT and contained discernable erythrocytes, presumably supplied from the retinal vessels. Conclusions: Although PDT may effectively provide closure of neovascularization in the choroid and expanding CNV membrane, CRAs continue to remain open. Vessel orientation (tangential versus radial) relative to the incident angle of the PDT laser beam may be a factor. Subsequently, viable CRAs conceivably might contribute to CNV revascularization following PDT.
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