Photodynamic therapy for corneal neovascularization.

BACKGROUND AND OBJECTIVE: Photodynamic therapy with tin ethyl etiopurpurin (SnET2) was evaluated as a treatment modality for rat corneal neovascularization. MATERIALS AND METHODS: Escalating light doses at 664 nm were applied focally to corneal neovascularization in rats 10 minutes following an intravenous injection of SnET2 using a low-power diode laser. Controls consisted of light-only and drug-only treatments. Clinical, angiographic, and histopathologic evaluations were performed on the animals up to 28 days after drug and/or light treatment. RESULTS: A drug and light dose-response was seen in producing neovessel closure. In animals treated with SnET2 and the highest light dose (25 J/cm2), all eyes showed occlusion at every follow-up evaluation up to 28 days. Control eyes demonstrated progressive disease at all time points. CONCLUSIONS: Photodynamic therapy appears to be safe and effective for eliciting prolonged (> 28 days) occlusion of corneal neovascularization in the rat model with minimal side effects and good clinical outcomes.

Ocular vascular thrombosis following tin ethyl etiopurpurin (SnET2) photodynamic therapy: time dependencies.

BACKGROUND AND OBJECTIVES: To evaluate the optimal time from the end of photosensitizer injection to the commencement of light application for creating characteristic fundus lesions and the time to vascular occlusion following photodynamic therapy (PDT) with tin ethyl etiopurpurin (SnET2). MATERIALS AND METHODS: Following intravenous injection of SnET2 0.5 mg/kg or lipid emulsion alone, the fundus of rabbits was irradiated at different times (5 to 240 minutes) after photosensitizer injection using 664 +/- 7-nm laser light with an irradiance of 354 mW/cm2 and fluence of 20 J/cm2. Ophthalmoscopy and fluorescein angiography were performed 1 day after SnET2 PDT. In separate groups of rabbits, treated areas of the fundus were imaged within 30 minutes following PDT using fluorescein vesicle and microsphere angiography with scanning laser ophthalmoscopy to document time of vascular occlusion. All animals were killed 1 day following treatment and eyes were examined by histopathology. RESULTS: Areas of hypofluorescence (indicating vascular occlusion) were seen when activating laser light was applied 5 to 20 minutes after SnET2 injection. Retinal vessels remained perfused in all cases. The time to vascular occlusion was 70 to 120 and 40 to 90 minutes in nonpigmented and pigmented rabbits, respectively. No safety issues were seen. CONCLUSION: PDT with SnET2 was effective in occluding the choriocapillaris. Activating light needs to be applied within a specific time frame after photosensitizer injection to achieve vascular occlusion.

Photodynamic therapy for choriocapillaris using tin ethyl etiopurpurin (SnET2).

BACKGROUND AND OBJECTIVE: To investigate the use of photodynamic therapy (PDT) using tin ethyl etiopurpurin (SnET2) for occluding the choriocapillaris in the eyes of pigmented rabbits. MATERIALS AND METHODS: Following intravenous injection of SnET2 (0.5 and 1 mg/kg) or lipid emulsion alone, the fundus of pigmented rabbits (n = 21) was irradiated starting 15 to 45 minutes after photosensitizer injection using 664-nm light at a fluence of 300 mW/cm2 and light doses of 5 to 20 J/cm2. Funduscopy, fluorescein angiography, and light and electron microscopy were performed at 1, 14, and 28 days after PDT. RESULTS: Following SnET2 and PDT, closure of the choriocapillaris was achieved with light doses as low as 5 J/cm2 (17 seconds) and a drug dose of 0.5 mg/kg of SnET2. Vascular occlusion was documented by fluorescein angiography and histology. Photodynamic damage was noted in the choriocapillary endothelial cells. Retinal pigment epithelial damage and outer retinal damage were also observed. No funduscopic, angiographic, or histologic findings were present in the eyes of pigmented control rabbits. CONCLUSIONS: PDT with SnET2 was effective in this animal model, using low levels of activating light for the occlusion of the choriocapillaris. This has clinical implications for the treatment of choroidal neovascularization and could be a more selective therapy than thermal laser photocoagulation.