Selective visualization of choroidal neovascular membranes

Laser-targeted angiography has unique advantages over conventional angiography of the fundus. Its efficacy in visualizing choroidal neovascular membranes was tested in a rat model and compared to that of fluorescein angiography.

Laser-targeted angiography was performed in rats with choroidal neovascularization (CNV) by injecting heat-sensitive carboxyfluorescein liposomes intravenously, locally releasing a bolus of dye in the choroid with a weak laser pulse, and recording advancement of the bolus on a video camera. Conventional fluorescein angiography also was performed.

Laser-targeted angiography revealed CNV as an abnormal pattern of brightly fluorescent vessels. The flow pattern of the bolus and histology, performed in some cases, confirmed the choroidal nature of the vessels. The angiographic visualization was not dependent on dye leakage through the vessels or staining of their walls. Laser-targeted angiography also provided visualization of new vessels that could not be diagnosed by fluorescein angiography. It demonstrated that blood flow was typically more sluggish in CNV than in normal choriocapillaris. Fluorescein angiography failed to demonstrate flow dynamics in all cases of CNV.

This study, in an animal model of CNV, shows that laser-targeted angiography demonstrates CNV and its flow dynamics in a manner not provided by conventional fluorescein angiography. It holds clinical promise as a method to delineate CNV considered difficult or impossible to detect by fluorescein angiography. The method also may permit selective photocoagulation of feeding vessels in the choroid, thereby limiting damage to the overlying retina.