Purpose. PDT using intravenous liposomal benzoporphyrin derivative (BPD) has been shown to close choroidal neovascularization (CNV). Persistence or recurrence of CNV may necessitate multiple treatments. We evaluated the effect of repeated photodynamic therapy (PDT) applications on normal primate retina and choroid. Methods. Three consecutive treatments over the center of the fovea or the optic nerve were evaluated. BPD was delivered by an intravenous infusion pump at doses of 6 mg/m2, 12 rng/m2, or 18 mg/m2. Laser irradiation was performed using a diode laser (689 nm) with an irradiance of 600 mW/cm2, fluence of 100 J/cm2, and spot size 4000 μm using a slit lamp delivery system. Findings were documented by fundus photography and fluorescein angiography at 24 hours and weekly and by light and electron microscopy at 2 or 3 weeks and 6 or 7 weeks after the third treatment. Results. Fluorescein angiography demonstrated early hypofluorescence with late staining 24 hours after treatment. A cumulative dose response was seen angiographically and histologically. More severe damage to the outer retina was noted at higher dye doses. Photodynamic therapy applied to the fovea or optic nerve using the 6 mg/m2 dose created minimal choriocapillaris damage and mild retinal pigment epithelium and outer photoreceptor damage. At this dose, the optic nerve showed mild atrophy and capillary loss. Treatment using the 12 mg/m2 and 18 mg/m2 doses led to choriocapillaris closure and severe retinal pigment epithelium and outer sensory retina damage. Severe vascular occlusion and hemorrhage within the optic nerve were present in the 12 mg/m2 and 18 mg/m2 eyes. Conclusion. Minimal damage to the retina, choroid, and optic nerve was present in primates treated with multiple PDT sessions using 6 mg/m2 liposomal BPD with irradiation timing and light doses kept constant. However, PDT using higher dve doses of 12 ma/m2 and 18 ma/m2 led to significant damaqe to the normal retina, choroid, and optic nerve.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience