PDT to monkey CNV with ATX-S10(Na): Inappropriateness of early laser irradiation for selective occlusion

PURPOSE. There is controversy about which mode of laser irradiation, early irradiation with low-dose photosensitizer or late irradiation with high-dos e, benefits the selective occlusion of choroidal neovascularization (CNV) i n photodynamic therapy (PDT). In this study, using an amphiphilic photosens itizer, 13,17-bis (1-carboxypropionyl) carbamoylethyl-8-etheny-2-hydroxy-3- hydroxyiminoetliylidene-2,7,12,18-tetraethyl porphyrin sodium (ATX-S10(Na); Photochemical Inc., Okayama, Japan), photodynamic and adverse effects of e arly irradiation on CNV-bearing monkey eyes were investigated. METHODs. Experimentally induced CNV lesions and normal retina were irradiat ed with a diode laser (670-nm wavelength) at a dose of I to 90 J/cm(2) at 1 to 19 minutes after intravenous injection of 2 mg/kg body weight of ATX-S1 0(Na). Vascular occlusion and CNV recurrence were evaluated by fluorescein and indocyanine green angiography and histologic analysis, until 4 weeks af ter irradiation. RESULTs. Of 45 different conditions, 23 did not induce CNV closure, 20 prov ided both CNV occlusion and retinal vessel damage, and 2 achieved selective CNV occlusion without retinal vascular injury. Recurrence of CNV was induc ed in 19 of 22 CNV-occluding conditions. ATX-S10(Na) angiography showed tha t dyes were similarly distributed between normal vessels and CNV at early t ime periods after injection, whereas they were preferentially accumulated i n CNV after 30 minutes. CONCLUSIONS. In PDT with ATX-S10(Na), irradiation within 20 minutes of dye injection failed to induce selective CNV occlusion, probably because there is no significant difference in the biodistribution of dye between CNV and retinal vessels. It also caused frequent CNV recurrence after extensive inf lammation in the irradiated retina.