Laser-triggered repetitive fluorescein angiography.

Liposome-encapsulated fluorescent dye has been altered to allow full fundus angiography after a single laser shot. By exposing the retinal arteries to laser energy where they emerge at the optic disc nerve head, dye release is elicited simultaneously in all four quadrants of the retina, without choroidal fluorescence, allowing visualization of the retinal microcirculation. Because the quantity of dye release is limited, recirculation does not increase background fluorescence. The procedure can be repeated many times without delay with consistent results. Increasing the laser spot size to 1.5 mm allows consistent dye release at energy densities from 0.5 J/cm2 to 3.4 J/cm2. This refinement will allow direct comparison in primates of this technique and conventional fluorescein angiography. The laser energy delivered to the retina is below suggested levels that may be tolerated by the optic nerve.