PHOTODYNAMIC THERAPY FOR ANTIFIBROSIS IN A RABBIT MODEL OF FILTRATIONSURGERY

BACKGROUND AND OBJECTIVE: The purpose of this pilot study was to inves tigate the use of photodynamic therapy (PDT) using tin ethyl etiopurpu rin (SnET2) as an adjunctive antifibrotic therapy for filtering surger y in a rabbit model. MATERIALS AND METHODS: The pharmacokinetics of Sn ET2 were established by intravenous (1 mg/kg) and subconjunctival (25, 50, or 75 mu g) injections and compared with controls. Intravenous an d subconjunctival SnET2 injections were given prior to posterior lip s clerectomies followed by postoperative laser irradiation (664 +/- 7 nm ; 100 mW/cm(2); 30 J/cm(2)). Antifibrotic efficacy was established by clinical response and histologic examination. RESULTS: After subconjun ctival injections, large areas of avascular conjunctiva were produced and filtering bleb survival was prolonged. No effect was found for int ravenously administered photosensitizer followed by light irradiation. CONCLUSIONS: PDT may be an alternative antifibrotic therapy for filtra tion surgery that does not use chemotherapeutic agents or ionizing rad iation. Multiple parameters (light, drug dose, irradiation area) may b e manipulated to improve predictability of the antifibrotic effect.