title: Surface-tension properties of hyaluronic Acid.
abstract: OBJECTIVE
  The maintenance of flow channels in the trabecular meshwork is dependent, in part, on the patency of the trabecular spaces. Because the amount of hyaluronic acid decreases in the trabecular meshwork of patients with primary open-angle glaucoma, a change in surface tension may be one of the effects of hyaluronic acid on aqueous outflow.
  
  
  METHODS
  The surface-active properties of hyaluronic acid (concentration of 0.156-2.5 mg/ml; molecular weights of 100,000, 500,000, and 4,000,000) in deionized water, Ringer's lactate, Ringer's lactate plus 0.06 mg/ml bovine serum albumin, and mock aqueous solution were tested using the drop volume method.
  
  
  RESULTS
  At a hyaluronic acid concentration of 0.312 mg/ml, surface tension decreased; at higher concentrations, a further decrease in surface tension was observed. In the presence of Ringer's lactate, the 100,000-MW hyaluronic acid was more active than the 4,000,000-MW hyaluronic acid. In the presence of Ringer's lactate plus bovine serum albumin or mock aqueous solution, the influence of surface tension of the 100,000-MW hyaluronic acid was moderated: with lower hyaluronic acid concentrations, the decline in surface tension was more than with Ringer's lactate, but with higher hyaluronic acid concentrations, the decline in surface tension was less than with Ringer's lactate. At high concentration, hyaluronic acid behaves like a non-Newtonian fluid, becomes more viscous, and may act to "seal" the trabecular space.
  
  
  CONCLUSIONS
  The results of this study indicate that hyaluronic acid possesses surface-active properties, which is just one of several properties of hyaluronic acid that may influence aqueous outflow resistance.
authors.affiliation: Laboratory for Oculo-Cerebrospinal Investigation, Children's Memorial Medical Center, and Department of Ophthalmology, Northwestern University Medical School, Chicago, Illinois, and Department of Ophthalmology, *New York Eye and Ear Infirmary, New York, New York, U.S.A.
authors.forename: P A
authors.initials: PA
authors.lastname: Knepper
authors.forename: S
authors.initials: S
authors.lastname: Covici
authors.forename: J R
authors.initials: JR
authors.lastname: Fadel
authors.forename: C S
authors.initials: CS
authors.lastname: Mayanil
authors.forename: R
authors.initials: R
authors.lastname: Ritch