Low-dose-rate ionizing irradiation for inhibition of secondary cataract formation

Introduction: Secondary cataract formation limits visual function after cat aract surgery. Various experimental methods utilizing the pharmacologic inh ibition of lens epithelial cell proliferation have been proposed. However, diffusion into the anterior chamber may lead to damage of corneal endotheli al cells. This study evaluated the inhibition of lens epithelial cell proli feration with a capsular bag ring, labeled with a beta -emitting radioisoto pe. Methods and Materials: In vitro studies using rabbit lens epithelial cells were performed to investigate the dose-dependent effect of irradiation. Bas ed on these results, P-32-labeled PMMA rings were implanted into the capsul ar bag of NZW rabbits in vivo after phacoemulsification. Animals were exami ned for development of posterior capsule opacification over a period of 12 weeks following surgery. Radiation damage to the surrounding ocular tissue was subsequently analyzed in histologic sections using TUNEL assay and prol iferation marker. Results: Irradiation of lens epithelial cells in vitro with >5 Gy resulted in a dose-dependent decrease in the number of cells. BrdU testing demonstra ted a near complete inhibition of cell proliferation, In vivo, implantation of P-32-1abeled PMMA rings led to inhibition of epithelial cell proliferat ion and secondary cataract formation but was not able to fully inhibit aber rant differentiation of some remaining cells. Histologic examination showed no evidence of radiation damage of the ciliary body or the corneal endothe lium, Conclusions: Low-dose beta irradiation exhibits the potential for inhibitio n of lens epithelial cell proliferation both in vitro and in vivo, Further investigation of various nuclides and their radiation profiles is needed to optimize the prevention of posterior capsule opacification due to epitheli al cell proliferation. (C) 2001 Elsevier Science Inc.