Quantitative Measurements of The Nasolacrimal Reflex: In the Normal and in Peripheral Facial Paralysis

Beyond the Ocular Surface: Nasal Sensory Input as a Driver of Reflex Lacrimation in Dogs

“…The magnitude and specificity of the reflex suppression observed in this study closely mirror findings in human medicine [1,2]. In people, nasal stimulation activates afferent fibers of the anterior ethmoidal and maxillary branches of the trigeminal nerve, which in turn engage the superior salivatory nucleus and parasympathetic efferents to the lacrimal gland [1].…”

“…The minimal change observed in the contralateral side following lidocaine treatment suggests that the canine NLR operates predominantly through an ipsilateral reflex arc, consistent with findings in human studies [1,2]. While slight reductions were noted in the untreated side of non-brachycephalic dogs, these changes did not reach statistical significance.…”

“…An a priori sample size calculation was performed using published STT-1 values in brachycephalic and non-brachycephalic dogs [3]. Assuming a 25%-30% reduction in tear production with attenuation of the nasolacrimal reflex (based on human studies) [1,2,6], we estimated that 5-6 brachycephalic dogs and 8-10 nonbrachycephalic dogs would be required to achieve > 80% power at a significance level (α) of 0.05. Thus, the total sample of 20 dogs provided adequate statistical power for this study.…”

Neurostimulation for dry eye disease

“…Several studies have corroborated the importance of the nasolacrimal reflex [37][38][39][40]. The Schirmer values for both eyes decreased 34% after right nasal mucosa anesthesia [41], suggesting a cross stimulation of tear secretion from the trigeminal afferent nerves on both sides. These findings were supported in patients with decreased sensation of the nasal mucosa, reduced nasal airflow, and tracheostomy who underwent dissection of the anterior ethmoidal branch of CNV 1 [38][39][40][41].…”

“…The Schirmer values for both eyes decreased 34% after right nasal mucosa anesthesia [41], suggesting a cross stimulation of tear secretion from the trigeminal afferent nerves on both sides. These findings were supported in patients with decreased sensation of the nasal mucosa, reduced nasal airflow, and tracheostomy who underwent dissection of the anterior ethmoidal branch of CNV 1 [38][39][40][41]. Sensory stimulation of the nasal mucosa significantly contributes to aqueous tear production in addition to neural stimulation from the ocular surface, suggesting that intranasal neurostimulation may constitute a beneficial therapeutic approach [42].…”