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 t o investigate two photosensitizers, tin ethyl etiopurpurin (SnET2) and tin octaethyl benzochlorin (BNZ 203), to determine their potential fo r creating ciliary body injuries during photodynamic therapy (PDT). MA TERIALS AND METHODS: The biodistribution of SnET2 (n = 10) and BNZ 203 (n = 9) was studied by fluorescence microscopy using a low light dete ction system, based on charged-coupled device photography, with digita l image processing at 1 and 24 hours after injection. PDT with SnET2 ( n = 8; 664 +/- 7-nm light; 75 mW/cm(2); 50 or 100 J/cm(2); l-mm spot s ize) and BNZ 203 (n = 6; 689 nm; 75 mW/cm(2); 50 or 100 J/cm(2); l-mm spot size) was performed at 24 hours post-injection. The control subje cts for SnET2 (n = 5) and BNZ 203 (n = 3) were given a maximal light d ose (100 J/cm(2)). RESULTS: Both photosensitizers demonstrated an intr avascular distribution at 1 hour that shifted to a ciliary body distri bution 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 sel ective injury to the rabbit ciliary body (SnET2 much greater than BNZ 203), with evidence of a small component of thermal damage (SnET2 grea ter than BNZ 203). CONCLUSIONS: PDT with SnET2 or BNZ 203 can produce selective injury to the pigmented rabbit ciliary body. The nonpigmente d ciliary body epithelium exhibits selective retention of SnET2. This finding warrants further investigation.