Anastomotic Vessels Remain Viable after Photodynamic Therapy in Primate Models of Choroidal Neovascularization

Abstract

Although PDT is effective in closing the choroidal neovascularization in FVT, this technique was ineffective in occluding anastomotic vessels and their associated tributaries within the mid- to proximal retina. Various factors (vascular diameter, composition, blood flow, orientation) may contribute to continued anastomotic patency. By convention, such vessels would typically be defined as chorioretinal anastomoses (CRAs); however, continuing studies suggest the possibility that these neovessels constitute dual-origin hybrids. Regardless of origin, viable anastomoses provide one potential mechanism for revascularization to occur after PDT and may help to explain why CRAs are considered a poor prognostic sign in patients with AMD.

Intravitreal Bevacizumab (Avastin) Treatment of Retinal Angiomatous Proliferation

“…Both laser photocoagulation and photodynamic therapy have been shown to be ineffective in most cases. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] The difficulty in treatment may be attributed to the high flow nature of these lesions, dual circulation from both the retina and the choroid, and the associated retinal pigment epithelial detachment that may constitute most of the lesion. In addition, there is a theoretical concern that photodynamic therapy may cause retinal vascular occlusion due to the extensive intraretinal leakage and fibrin deposition associated with RAP.…”

Chorioretinal anastomosis and photodynamic therapy:a two-year follow-up study

“…The rate of recurrences increased with longer follow-up. Possible reasons for recurrences may include, according to Criswell [4]: 1-relatively higher retinal blood flow rate in the proximal retina; 2-sustained arterial pressure of retinal blood vessels resulting in distension of both retinal and anastomotic trunks, after PDT occlusion; 3-PDT, although effective in occluding smaller diameter new vessels of choroidal origin (up to approximately 5 μm diameter), may not be effective in blocking larger diameter blood vessels (5 μm diameter and larger). CRA is a particular form of neovascular AMD.…”

“…The efficacy of PDT in eyes with CRA has been questioned by some authors [4,9]. No data are available from randomized, multicentre clinical trials like TAP, VIP or VISION because ICG was not used and CRA was not identified as clinical entity.…”

Polypoidal Choroidal Vasculopathy and Retinochoroidal Anastomosis in Japanese Patients Eligible for Photodynamic Therapy for Exudative Age-Related Macular Degeneration

“…31 Additionally, clinical data from in vivo experiments reported that RCA is associated with a poor response of CNV to PDT. 46 Therefore it is important to diagnose RCA before using PDT, and, in addition to FA, ICGA is recommended to help detect RCA and its associated findings.…”