What causes dry eye syndrome?

Jeffrey Gilbard, MD, conducting research sponsored by the National Eye Institute, has proven that dry eye is caused by any condition that increases tear film evaporation, or by any condition that decreases tear production.  These conditions, in turn, may be caused by a dietary deficiency of omega-3 essential fatty acids.

Evaporation can increase from chronic eye lid inflammation or "blepharitis," specifically posterior blepharitis or meibomitis.  In this condition the oil glands in the eye lid become damaged as a result of inflammation, and oil production decreases.  With decreased oil on the tear film there is increased evaporation.

Evaporation can also increase from having large eyes either on a hereditary basis (as in "my, you have big beautiful eyes"), or from thyroid eye disease.  The larger the eyes, the larger the surface area for evaporation, the greater the evaporation and the greater the loss of water.

Tear production can decrease from any condition that damages the lacrimal gland.  The most common cause of lacrimal gland damage is Sjögren's  syndrome.  Patients with primary Sjögren's syndrome also have dry mouth.  Patients with secondary Sjögren's  syndrome have an associated autoimmune condition such as rheumatoid arthritis.

Tear production can also decrease from any condition that decreases corneal sensation.  Just as irritated eyes tear more, eyes that lose sensation tear less.  This is because intact corneal sensation partially drives tear production.  Causes for decreased corneal sensation include long-term contact lens wear, LASIK eye surgery, trauma to the 5th nerve, and certain viral infections.

Omega-3 essential fatty acids are provided primarily by the consumption of salmon, herring, sardines and mackeral.  For those who can't, won't or don't eat these on a regular basis, there is TheraTears Nutrition an omega-3 supplement developed for dry eyes and blepharitis.