The development of vitreous membranes and retinal detachment induced by intravitreal carbon microparticles

We induced intravitreal cellular proliferation by injection of carbon microparticles (size 20-70 nm) into the vitreous of 21 eyes of 11 cynomolgus monkeys. Pathological changes were evaluated by light and electron microscopy. At 1 week, there was conspicuous cyclitis showing exudative separation of the nonpigmented and pigmented ciliary epithelium, inflammatory cells, mononuclear phagocytes, and premacular vitreous detachment. At 3 weeks, continued macrophagic response was accompanied by fibrovascular proliferation with ingrowth of vessels from the ciliary body into the vitreous. At 4-5 weeks, deposition of extracellular fibrous material and traction retinal detachment (RD) were found. At 10 weeks, all eyes had extensive RD with pre- and subretinal collagenous cellular membranes. Carbon-laden macrophages were aggregated over the optic disc and fovea with prepapillary neovascularization and cystoid macular edema. Thus, intravitreal fibrovascular proliferation, vitreous contraction, and RD were induced by inflammatory and phagocytic response to carbon particles.