Identification and Treatment of Feeder Vessels in Macular Degeneration

Age-related macular degeneration (AMD) represents the most common cause of blindness in patients over the age of 60. Most vision loss in this disease results from sequelae of choroidal neovascular membrane (CNVM) formation. CNVM is usually composed of well-formed neovascularization and occult (less well-formed) neovascularization. While clinical trials have shown that some patients, mostly those with well-formed CNVM, may benefit from laser photocoagulation or photodynamic therapy, at present there is no treatment for patients who have combined CNVM lesions (both well-formed and occult) whose area of occult neovascularization is greater than 50% or who have other presentation of CNVM such as pigment-epithelial detachment or neovascular fibrosis. Retinal histopathology of patients with choroidal neovascularization has revealed that areas of CNVM are usually fed by a few smaller choroidal feeder vessels originating from the choroid or choriocapillaris. Therefore, it has been hypothesized that closure of these feeder vessels would infarct the large CNVM complex. Until recently, identification of these feeder vessels has been difficult but new high speed indocyanine imaging of the choroid (Phi-motion) indocyanine green angiography (ICG) has allowed for more precise detection of these vessels. We will test this hypothesis by utilizing Phi-motion ICG to identify choroidal feeder vessels in patients with CNVM not amenable to approved treatments. If feeder vessels are identified, then pulse-diode laser photocoagulation will be used to attempt closure of these vessels. The study is designed to provide information on the feasibility of standardizing this procedure and estimating its potential efficacy. The primary outcome will be a greater than 50% reduction in the area of leakage from the neovascular component as determined by fluorescein angiogram. Secondary outcomes will include a complete resolution of leakage measured by fluorescein angiography, the number of repetitive laser treatments undergone, the number of patients eligible by fluorescein angiogram but without identifiable feeder vessels, and the number of patients with vision loss, from baseline, of 15 letters or more, 30 letters or more, or are reduced to less than 5 letters read. All adverse events regardless of severity or relatedness to the therapy will be collected and summarized. Assessment of all outcomes will be made at 6 weeks, 3, 6, 12, 18, and 24 months post laser treatment, and 24 months after enrollment. This study will give investigators some insight into this technology and the feasibility of this treatment in patients with various forms of neovascular AMD. In addition, the results of the study will provide the foundation for larger studies of this therapy.