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Surface activity determination of aqueous tear components in dry eye patients and normals

1977; Elsevier BV; Volume: 24; Issue: 5 Linguagem: Inglês

10.1016/0014-4835(77)90269-x

1096-0007

Frank J. Holly, James T. Patten, Claes H. Dohlman,

Surfactants and Colloidal Systems

A micromethod based on contact angle goniometry has been developed to study surface activity changes in aqueous tear components of tear samples of 5 μl or even less. This method was used to investigate the effect of dilution and relative mucin content on the combined surface activities of tear components and tear component analogues. The following determinations were made: (1) the decrease in tension of a water-nonpolar interface due to adsorption of tear components; (2) the wettability by tears of a layer of surface-active tear components adsorbed on a nonpolar solid; (3) the approximate surface tension of the aqueous tears. The tears examined by this method were obtained from normals and from patients suffering from ocular pemphigoid, mild keratoconjunctivitis sicca, and Stevens-Johnson syndrome. A slight decrease was observed in the combined surface activity of the tear components in tears from patients with ocular pemphigoid and keratoconjunctivitis sicca. This is attributed to a moderate decrease of the relative mucin content of the aqueous tears. The deviation from normal of tear component surface activity thus detected was insufficient to account for the tear film instability observed in these dry eye states. A significantly increased surface activity for tear components in tears from Stevens-Johnson patients was found. This is probably effected by unidentified inflammation products. The decrease in the wettability of the adsorbed tear components from tears of the sicca patients was attributed to the increased lipid contamination of the macromolecular tear components. It must be emphasized that composition and surface activity of the tear components do not offer information on the continuity and thickness of the underlying mucus layer of the tear film. These two layers are not even in equilibrium because of the low mobility of the macromolecules and the disturbing effect of frequent lid motion. Thus, the mucus layer in the dry eye states associated with reduced goblet cell population can be inadequate despite nearly normal tear composition and tear component surface activity, resulting in premature tear film breakup.