A MODEL OF CHRONIC HYPOTONY IN THE RABBIT

. Background: Chronic hypotony is an important cause of functional fai lure after proliferative vitreoretinopathy (PVR) surgery even if the r etina is successfully reattached. The purpose of this study was to cre ate a relevant model of chronic hypotony in the rabbit. . Methods: Eig hteen pigmented rabbits weighing 3-4 kg were used in our experiment. W e performed pars plana lensectomy on 14 eyes of 14 rabbits with a frag matome and a vitreous cutter. At the end of surgery, we injected 0.2 m l of phosphate-buffered saline containing 100000 cultured rabbit derma l fibroblasts over the epiciliary area. As a control, we performed par s plana lensectomy alone on four eyes of four rabbits. The intraocular pressure (IOP) was measured on days 7, 14, 21, 28. Two rabbits were k illed on day 7 and prepared for histology. Two additional rabbits were killed on day 14, and the remaining ten rabbits were killed on day 28 . . Results: All 14 eyes following lensectomy and fibroblast injection had an IOP less than 5 mm Hg on each follow-up and a mean of 2.5+/-0. 6 mm Hg (mean+/-SD) on day 28. Four control eyes with lensectomy alone had an IOP of 7.5+/-2.1 mm Hg on day 28 (P<0.05). On gross examinatio n, we identified a variety of pathologic changes, including the develo pment of a fibrous translucent epiciliary membrane that caused distort ion of ciliary processes, iridociliary adhesion and anterior displacem ent of the peripheral retina on day 28. Microscopic examination of eye s obtained on day 28 showed changes in the ciliary epithelium that inc luded absence or atrophy of the non-pigmented ciliary epithelium, atro phy and cystic vacuolization of the pigmented ciliary epithelium, and in terstitital edema of the ciliary body stroma. . Conclusion: We have created a model of chronic hypotony with epiciliary membrane using cu ltured fibroblasts in the rabbit. This model may be useful to help elu cidate the pathophysiology of chronic hypotony and to investigate pote ntial treatments.