Histologic examination was made of 1,419 globes from domestic animals (964 dogs, 374 cats, 41 horses, and 40 cattle) with ocular disease; pre-
iridal membranes (rubeosis iridis) were found in 98. The membranes originated as endothelial budding from the anterior
iridal stroma and seemed to mature into fibrous or fibrovascular membranes that were often followed by
hyphema or, occasionally,
glaucoma. Pre-existent disease in the 98 affected globes included chronic
endophthalmitis (27/98), chronic
glaucoma (24/98), anterior
uveal melanoma (15/98), ciliary body
adenoma (14/98),
neoplasms metastatic to the eye (8/98), and chronic
retinal detachment (6/98). In terms of likelihood of occurrence, pre-
iridal membranes seen in 21% (6/21) of globes with
retinal detachment, 19% (14/75) of those with ciliary body
adenomas, 14% (24/167) of those with chronic
glaucoma, and 10% (15/158) of those with anterior
uveal melanoma. They were detected with greatest relative frequency in horses (9/41) followed by dogs (83/964), cats (5/374) and cattle (1/40). These membranes, which are rarely detected by clinical examination, probably form in response to angiogenic factors released by ischemic retina, by
neoplasms, or by leukocytes involved in ocular
inflammation.