HA is a major component of the vitreous body, and a key macromolecule in ophthalmology.It improves the effect of pilocarpine on miosis and facilitates delivery of gentamicin sulfate for the treatment of severe ocular infections.HA has been also used in assisting excimer laser surgeries for the correction of irregular astigmatism resulting from previous corneal refractive surgery, being able to cover depressions and irregularities from the previous surgery.Currently, a number of preparations, of varying molecular size HA chains, are available, including an HA and chondroitin sulfate combination, termed Viscoat.Its major use, however, is as a substitute or replacement for the vitreous fluid lost during procedures such as cataract surgery or lens placement.For many years, Healon, derived from rooster combs, manufactured initially by Biotics, Inc.This preparation was also used as a viscoelastic protector of the corneal endothelium during corneal transplantation.