To localize choroidal lesions demonstrated by indocyanine green (ICG) angiography, retinal blood vessels must be identified. Since retinal blood vessels are seen in early-phase ICG angiography and the choroidal lesions are best seen on the late-phase images, a technique has been developed to demonstrate retinal blood vessels in the late phase of the ICG angiography study. The technique requires the injection of 0.3 mg of ICG dye mixed in 3.0 cc of diluent. This injection is given between 30 and 40 minutes into the ICG angiogram. This technique allows visualization of retinal blood vessels, which can be used as landmarks to localize choroidal lesions. Additionally, this technique, when combined with newly developed computer software programs, permits the mapping and tracing of choroidal lesions of the fundus.