The effect of ageing and disease on tear constituents.

An ELISA method is described for measuring the age-related changes of tear lysozyme, lactoferrin, ceruloplasmin, IgA and IgG in normal eyes. The normal levels for these proteins at each age are compared with those from patients with dry and 'questionably dry' eyes, which each have individual profiles, as well as with patients suffering from ocular pemphigoid, chronic non-ulcerative blepharitis and meibomianitis. Results of tear lysozyme assays from patients on various beta-blockers are discussed with the suggested hypothesis that stimulation of beta-receptors per se in the human lacrimal gland is not required for tear protein secretion. The importance of other proteins present in the tear fluid is reviewed.