Dry eye syndrome (DES) represents a heterogeneous group of conditions that share inadequate lubrication of the ocular surface as their common denominator. DES is characterized by symptoms of ocular dryness and discomfort due to insufficient tear quantity or quality caused by low tear production and/or excessive tear evaporation. Symptoms can be debilitating 1 and, when severe, may affect psychological health and ability to work. No cure exists for DES, which is one of the leading causes of patient visits to ophthalmologists and optometrists in the United States. Because of the presumed high prevalence of DES and the attendant health care burden, the National Eye Institute (NEI) has identified tear film and dry eye research as important areas in need of further study.