Proctase-treated collagen vitreous substitutes were evaluated in monkey eyes. Nonirradiated viscous collagen solutions formed cloudy white opacities immediately after injection into the vitreous cavity. The vitreous turbidity did not completely clear during two years of observation. Collagen gels, formed by ultraviolet irradiation of collagen solutions, remained clear after injection but lacked the rigidity desired for retinal detachment surgery. The solutions and gels both produced a transient inflammatory response, but no destructive sequelae were noted.
Pruett RC, Calabria GA, Schepens CL. Collagen Vitreous SubstituteI. Experimental Study. Arch Ophthalmol. 1972;88(5):540-543. doi:10.1001/archopht.1972.01000030542015