The pathology of dry eye

Homeostasis of the tear film involves delicate hormonal and neuronal regula tory mechanisms. The eye appears to be a target organ for sex hormones, par ticularly the androgens, as they modulate the immune system and trophic fun ctions of the lacrimal glands and the functioning of the meihomian glands T he cornea, lacrimal glands, mucous cells, and meibomian glands are all rich ly innervated, indicating the importance of nervous regulation in their fun ction. Parasympathetic, sympathetic, and sensory innervation play complex s timulatory or inhibitory roles, and neuronal pathways interact via complex surface results cascades. abnormalities at any point in these pathways can cause overall dysregulation of lacrimal function. Whatever the initial caus es of dry eye, chronic dryness of the ocular surface results in inflammator y reactions and gradual destruction of the lacrimal glands and conjunctival epithelium. Once dry eye disease has developed, inflammation is the key me chanism of ocular surface injury, as both the cause and consequence of cell damage. In practice, dry eye can be associated with Sjogren's syndrome, al lergies, infection, blepharitis, and preservative-containing eye drops. (Su rv Ophthalmol 45(Suppl 2):S211-20, 2001. (C) 2001 by Elsevier Science Inc. All rights reserved).