Walsh & Hoyt: Reflexes Associated with Lacrimation

Most reflex lacrimation originates from stimulation of the first division of the trigeminal nerve. The stimulus, if slight, may produce only ipsilateral lacrimation, but beyond a certain point it will affect both eyes. These stimuli include all painful diseases of the eye, corneal foreign bodies, and corneal irritants. Many nonocular sources of trigeminal stimulation produce lacrimation. These include tickling of the nasal mucous membrane, painful teeth, and painful sinus disease. Trigeminal-lacrimal reflexes may operate through brain stem connections between the descending spinal tract of the trigeminal nerve and the superior salivatory nucleus.