Abstract: An ultra-pure, high molecular weight hyaluronic acid fraction which is characterized by the absence of significant cellular infiltration of the vitreous and anterior chamber, absence of significant flare in the aqueous humor, absence of significant haze or flare in the vitreous and absence of pathological changes to the cornea, lens, iris, retina, and choroid of the owl monkey eye when one milliliter of a 1% solution of the sodium salt thereof dissolved in physiological buffer is implanted in the vitreous replacing about one-half the existing liquid vitreous. This material is obtained from animal tissue containing hyaluronic acid by a process which comprises removing the blood from animal tissue containing hyaluronic acid, extracting hyaluronic acid therefrom, deproteinizing the hyaluronic acid extract, and removing any unidentified inflammation causing agents persent therein by treating the deproteinized hyaluronic acid extract at a pH of 6.0 - 7.