Preclinical evaluation of photodynamic therapy to inhibit lens epithelial proliferation

Sixteen rabbits underwent endocapsular phacoemulsification. To evaluate the effect of photodynamic therapy (PDT) on retained capsular cells, 14 of the 16 animals were randomized to four groups, following lensectomy: lensectomy alone, light alone (56 J at 510 nm), drug alone (100 μg/ml Photofrin II), and PDT (100 μg/ml Photofrin II + 56 J at 510 nm). Slit lamp photography documented a gradual reduction of lens capsule clarity from three to five weeks. Histology of the lens capsule revealed viable lens fiber cells, epithelial cells, and fibrous proliferation in all groups. In addition, two animals were used in pilot studies to evaluate the potential enhancement of the photodynamic effect, one employing a Healon-Photofrin II mixture and a Photofrin II-conjugate of a polyclonal antibody raised against lens epithelial membranes. Use of these latter two agents, with extended photo-irradiation (120 J) resulted in local epithelial and fiber cell death. Efflux of these agents from the capsule resulted in local ocular toxicity, viz., uveitis and corneal edema. Effective inhibition of lens cell proliferation after lensectomy with PDT will require capsular containment of the photoreactive agent, and a method for uniform light delivery within the capsule during photo-irradiation.