PHOTODYNAMIC THERAPY (PDT) OF THE CILIARY BODY WITH SILICON NAPHTHALOCYANINE (SINC) IN RABBITS

Background and Objective: To investigate silicone naphthalocyanine (SI Nc; 0.5 mg/kg) for photodynamic therapy (PDT) of the ciliary body in p igmented rabbits. Study Design/Materials and Methods: SINc was dissolv ed in canola oil by heating, emulsified with Tween-80, and given by ea r vein. Pharmacokinetics were studied in frozen sections by fluorescen ce microscopy using a CCD camera-based, low light detection system wit h digital image processing at 1 hr and 24 hr (12 rabbits, 24 eyes tota l). A Ti:Sapphire laser delivered light at 770 nm by contact fiberopti c (1,000 mu m; 80 mW/cm(2);20,40 and 80 J/cm(2)). Controls (5 rabbits) , received laser light at 770 nm without SINc. For comparison, eyes re ceived continuous wave Nd:YAG laser by fiberoptic contact (0.8-1.2 J). Results: Localization studies showed intravascular distribution shift ing to a ciliary body distribution at 24 hr, PDT at 1 hr and 24 hr pos tinjection showed a more selective destruction of the ciliary body at 24 hr. Ciliary processes treated at 24 hr showed infarction and marked edema with sparing of iris. Tissue thermal damage was minimal in PDT controls. Eyes treated with the Nd:YAG laser exhibited full-thickness thermal necrosis of iris, ciliary processes, and a fibrinous iridocycl itis. In contrast, eyes treated by PDT were quiet with thrombosis of s uperficial blood vessels. Conclusion: Tissue photon penetration is goo d at 770 nm and thermal effects from the exciting laser alone were min imal. The ciliary processes of pigmented rabbits exhibit a selective r etention of SINc and on that basis can be selectively destroyed with a minimum on thermal damage to nontarget tissues. (C) 1996 Wiley-Liss, Inc.