Theoretical investigation of the role of choriocapillaris blood flow in treatment of subfoveal choroidal neovascularization associated with age-related macular degeneration

PURPOSE: To investigate the relationship between choriocapillaris blood flo w and blood flow through an overlying choroidal neovascularization, as it r elates to photocoagulation-induced changes in the choriocapillaris circulat ion. METHODS: A theoretical model that simulates the blood now in the choriocapi llaris and choroidal neovascularization of the human eye was developed, bas ed on histologically determined vascular geometry and experimentally measur ed blood pressure gradients. The choriocapillaris blood pressure and blood flow were examined before and after simulated photocoagulation of various S attler layer vessels entering the choriocapillaris in the vicinity of the c horoidal neovascularization, (The Sattler layer is the inner layer of mediu m-sized choroidal vessels that includes both arterioles and venules that su pply the choriocapillaris.) RESULTS: The theoretical model showed that both partial and complete occlus ion of either Sattler arteriole or venous vessels in the vicinity of the ca pillary-like vessels connecting a choroidal neovascularization to the under lying choriocapillaris results in significant choroidal neovascularization blood flow reduction. These theoretical results are similar to clinically o bserved changes induced by laser photocoagulation of feeder vessels. (In th is discussion, the term "feeder vessels" refers to those vessels in an indo cyanine green angiogram image that appear to supply blood to a choroidal ne ovascularization; these vessels appear to be Sattler layer vessels, rather than the histologically demonstrated short, capillary-like vessels that for m choriocapillaris-choroidal neovascularization communications.) CONCLUSIONS: Reduction of choriocapillaris blood now underlying a choroidal neovascularization may be sufficient to reduce the blood flow rate in the choroidal neovascularization and thereby reduce the associated retinal edem a. The results also suggest that reduction of choriocapillaris blood flow m ay be the common hemodynamic event associated with the successful applicati on of several currently practiced methods of choroidal neovascularization t reatment, including feeder vessel photo coagulation, photodynamic therapy, transpupillary thermotherapy, and prophylactic drusen photocoagulation. Ult imately, this model may be useful in determining optimal placement of laser photocoagulation burns to achieve a desirable perturbation in choroidal bl ood flow distribution and thereby reduce choroidal neovascularization blood flow to the extent necessary to obliterate associated retinal edema. (Am J Ophthalmol 2001; 132:85-93. (C) 2001 by Elsevier Science Inc. All rights r eserved).