Optimizing treatment of choroidal neovascularization feeder vessels associated with age-related macular degeneration

Abstract

PURPOSE: To optimize the method of treating choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD). DESIGN: Experimental study and interventional case series. METHODS: The parameters associated with locating and then photocoagulating CNV feeder vessels were identified and optimized using published data and data derived from modeling the choroidal vasculature. Based on these optimized parameters, a prototype diagnostic/treatment system was designed that captures high-speed indocyanine green (ICG) angiogram images and facilitates analysis of the images by enhancing visualization of dye movement through CNV feeder vessels (FVs). The system also permits precise aiming and delivery of 810- nm wavelength photocoagulation laser energy to target FVs on a real-time ICG angiogram image of the choroidal vasculature. Target FVs are tracked by a joy-stick controlled laser aiming beam until an intravenously-injected high-concentration ICG dye bolus is observed to enter the target vessel, at which time the laser is fired. Proof of principle of the combined diagnosis/treatment system design for performing dye-enhanced photocoagulation (DEP) in the clinical setting and determination of the minimum DEP laser energy needed to close CNV FVs was made in 11 AMD patients requiring treatment of CNV, but for whom other treatment was not appropriate. RESULTS: Using ICG—DEP, CNV feeder vessels were closed with single pulse laser energy, delivering as little as 0.6 to 1.8 J of energy to the fundus, producing no visible change in the fundus. Successful FV closure was usually indicated immediately by presence of incarcerated ICG dye in the vessel adjacent to the burn site. The prototype system proved relatively easy to operate. After acquiring and interpreting diagnostic angiograms and repositioning a patient in front of the device, feeder vessel DEP and treatment evaluation required 15 to 20 minutes. CONCLUSIONS: Indocyanine green dye-enhanced photocoagulation of CNV feeder vessels, facilitated by use of a device that permits real-time visualization of the choroidal circulation while aiming the treatment laser beam, appears to minimize the amount of energy applied to the fundus and the volume of fundus tissue affected by treatment, compared with other treatment modalities. The combination diagnosis/treatment device should be useful in optimizing FV treatment and in refining and evaluating the efficacy of DEP in future clinical trials.