Bron A J
Nuffield Laboratory of Ophthalmology, Oxford.
Eye (Lond). 1988;2 ( Pt 2):164-71. doi: 10.1038/eye.1988.30.
Tears are necessary for the continued health of the ocular surface. Normal constituents include water, mucin, and lipids, electrolytes, non-electrolytes, and proteins. Lacrimal secretion is under cholinergic control and modulated by sympathetic adrenergic, peptidergic (VIP) and humoral influences; the meibomian glands are innervated, but the goblet cells are not. Retinoids are important for ocular health and prealbumin may be a carrier for vitamin A in the tears to supply corneal epithelium with its requirements. Changes in tear constituents may cause certain ocular disorders. In dry eyes increased osmolarity is thought to cause surface ocular damage but the presence of granulocytes and inflammatory mediators such as prostaglandins and super-oxide may contribute to inflammatory events in this and other external diseases.
眼泪对于眼表的持续健康是必需的。正常成分包括水、黏蛋白、脂质、电解质、非电解质和蛋白质。泪液分泌受胆碱能控制，并受交感肾上腺素能、肽能（血管活性肠肽）和体液影响的调节；睑板腺受神经支配，但杯状细胞不受神经支配。类视黄醇对眼部健康很重要，前白蛋白可能是泪液中维生素A的载体，以满足角膜上皮的需求。泪液成分的变化可能导致某些眼部疾病。在干眼症中，渗透压升高被认为会导致眼表损伤，但粒细胞以及前列腺素和超氧化物等炎症介质的存在可能会促成这种疾病和其他外部疾病中的炎症反应。
