The pathogenesis is multifactorial, but is broken down into aqueous deficiency (inadequate lacrimal gland function) and increased evaporative state (insufficient lipophilic tear layer which normally prevents aqueous tear evaporation) (2007). Aqueous deficiency may be related to normal aging, hormonal imbalances, collagen vascular disease, autonomic neuropathy, systemic or local inflammatory conditions, systemic medications, or vitamin deficiency. Increased evaporative states may be caused by blepharitis (meibomitis especially), ineffective blinking or abnormal lid anatomy (ectropion), topical medications, contact lens wear, or surface inflammation.