Aqueous tear deficiency	Evaporative tear deficiency
• Sjögren syndrome	• Meibomian gland dysfunction (posterior blepharitis)
• Age-related dry eye	• Exophthalmos, poor lid apposition, lid deformity
• Systemic medications (e.g. antihistamines, beta blockers, antispasmodics, diuretics)	• Low blink rate
• Lacrimal gland duct obstruction (e.g cicatricial pemphigoid, mucous membrane pemphigoid, trachoma, erythema multiforme, burns)	• Ocular surface disorders (e.g. vitamin A deficiency, toxicity from topical drugs/preservatives, contact lens wear)
• Ocular sensory loss leading to reflex hyposecretion (e.g. diabetes mellitus, corneal surgery, contact lens wear, trigeminal nerve injury)	• Ocular surface disease (e.g. allergic conjunctivitis)
• Lacrimal gland infiltration (e.g. sarcoid, lymphoma, graft vs host disease, AIDS, IgG4-related disease)