Treatment of experimental preretinal neovascularization using photodynamic thrombosis

Retinal or preretinal neovascularization (NV) is the result of many ischemic conditions of the retina and is an important factor leading to severe visual loss in diabetic retinopathy. Panretinal photocoagulation does not always control its growth or bleeding sequelae. A potential new treatment modality, photodynamic therapy (PDT), was evaluated for limiting the progression of experimental NV in the rabbit eye. The NV was produced by injecting cultured dermal fibroblasts into the preretinal vitreous space after combined enzymatic and mechanical vitreolysis. This method results in traction retinal detachment with a rapid and consistent growth of NV. After administration of the photosensitizing dye rose bengal (20 mg/kg intravenously), PDT was done using a slit-lamp light source focused through a fundus contact lens (45 J/cm2). The NV was treated on two separate occasions during the active phase of growth (on days 13 and 21 after fibroblast injection). Control animals were exposed to light before injection of rose bengal. Eight randomly assigned animals in each group were followed between treatments and for 28 days after the second treatment. The appearance of NV was documented by frequent photography and fluorescein angiography. The PDT resulted in thrombosis of NV for at least 3 days. Reperfusion, however, was consistently noted at 7 days. Thrombosis was associated with a delay in the growth and maturation of NV fronds, which resumed after reperfusion. Twenty-eight days after the second treatment, NV in both experimental and control eyes had undergone atrophy. At that time (the conclusion of follow-up), however, the size of treated NV fronds (estimated from computerized image analysis of fluorescein angiograms) was significantly less than that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)