Photodynamic therapy of the ciliary body with tin ethyl etiopurpurin and tin octaethyl benzochlorin in pigmented rabbits.

BACKGROUND AND OBJECTIVES: The authors used a pigmented rabbit model to investigate two photosensitizers, tin ethyl etiopurpurin (SnET2) and tin octaethyl benzochlorin (BNZ 203), to determine their potential for creating ciliary body injuries during photodynamic therapy (PDT). MATERIALS AND METHODS: The biodistribution of SnET2 (n = 10) and BNZ 203 (n = 9) was studied by fluorescence microscopy using a low light detection system, based on charged-coupled device photography, with digital image processing at 1 and 24 hours after injection. PDT with SnET2 (n = 8; 664 +/- 7-nm light; 75 mW/cm2; 50 or 100 J/cm2; 1-mm spot size) and BNZ 203 (n = 6; 689 nm; 75 mW/cm2; 50 or 100 J/cm2; 1-mm spot size) was performed at 24 hours post-injection. The control subjects for SnET2 (n = 5) and BNZ 203 (n = 3) were given a maximal light dose (100 J/cm2). RESULTS: Both photosensitizers demonstrated an intravascular distribution at 1 hour that shifted to a ciliary body distribution at 24 hours (SnET2 much greater than BNZ 203). In addition, the SnET2 demonstrated suborgan localization to the nonpigmented ciliary body epithelium. Both photosensitizing agents were able to produce selective injury to the rabbit ciliary body (SnET2 much greater than BNZ 203), with evidence of a small component of thermal damage (SnET2 greater than BNZ 203). CONCLUSIONS: PDT with SnET2 or BNZ 203 can produce selective injury to the pigmented rabbit ciliary body. The nonpigmented ciliary body epithelium exhibits selective retention of SnET2. This finding warrants further investigation.

Photodynamic therapy for antifibrosis in a rabbit model of filtration surgery.

BACKGROUND AND OBJECTIVE: The purpose of this pilot study was to investigate the use of photodynamic therapy (PDT) using tin ethyl etiopurpurin (SnET2) as an adjunctive antifibrotic therapy for filtering surgery in a rabbit model. MATERIALS AND METHODS: The pharmacokinetics of SnET2 were established by intravenous (1 mg/kg) and subconjunctival (25, 50, or 75 micrograms) injections and compared with controls. Intravenous and subconjunctival SnET2 injections were given prior to posterior lip sclerectomies followed by postoperative laser irradiation (664 +/- 7 nm; 100 mW/cm2; 30 J/cm2). Antifibrotic efficacy was established by clinical response and histologic examination. RESULTS: After subconjunctival injections, large areas of avascular conjunctiva were produced and filtering bleb survival was prolonged. No effect was found for intravenously administered photosensitizer followed by light irradiation. CONCLUSIONS: PDT may be an alternative antifibrotic therapy for filtration surgery that does not use chemotherapeutic agents or ionizing radiation. Multiple parameters (light, drug dose, irradiation area) may be manipulated to improve predictability of the antifibrotic effect.