A model of chronic hypotony in the rabbit

Chronic hypotony is an important cause of functional failure after proliferative vitreoretinopathy (PVR) surgery even if the retina is successfully reattached. The purpose of this study was to create a relevant model of chronic hypotony in the rabbit.

Eighteen pigmented rabbits weighing 3-4 kg were used in our experiment. We performed pars plana lensectomy on 14 eyes of 14 rabbits with a fragmatome and a vitreous cutter. At the end of surgery, we injected 0.2 ml of phosphate-buffered saline containing 1,00,000 cultured rabbit dermal fibroblasts over the epiciliary area. As a control, we performed pars plana lensectomy alone on four eyes of four rabbits. The intraocular pressure (IOP) was measured on days 7, 14, 21, 28. Two rabbits were killed 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.

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 examination, we identified a variety of pathologic changes, including the development of a fibrous translucent epiciliary membrane that caused distortion of ciliary processes, iridociliary adhesion and anterior displacement of the peripheral retina on day 28. Microscopic examination of eyes obtained on day 28 showed changes in the ciliary epithelium that included absence or atrophy of the non-pigmented ciliary epithelium, atrophy and cystic vacuolization of the pigmented ciliary epithelium, and interstitial edema of the ciliary body stroma.

We have created a model of chronic hypotony with epiciliary membrane using cultured fibroblasts in the rabbit. This model may be useful to help elucidate the pathophysiology of chronic hypotony and to investigate potential treatments.