Neurostimulation for tear production.

PURPOSE OF REVIEW: Dry eye disease (DED) is a chronic multifactorial disease that affects millions of people worldwide. Despite ongoing research, treatment for DED remains a challenge. Neurostimulation for tear production is a rapidly evolving field that culminated in the development of the intranasal tear neurostimulator (ITN). In this article, we review the neuroanatomy and pathophysiology of tear production and the evolution of neurostimulation for the treatment of DED. RECENT FINDINGS: The ITN was approved for commercial use in April 2017. This innovation stemmed from the success of lacrimal nerve and anterior ethmoid nerve stimulation animal studies. Since then, numerous pilot studies and multicenter randomized controlled trials demonstrate increased aqueous tear production, improved DED-related symptoms, and device safety. Recent studies also report the positive effects of intranasal stimulation on mucin and lipid secretion. SUMMARY: Neurostimulation for enhanced tear production is a promising new treatment option for DED. Stimulation of the lacrimal nerve and anterior ethmoid nerve both effectively increase tear volume. The ITN is a noninvasive device that effectively increases aqueous tear volume and may improve tear composition, including mucin and lipid concentrations. Further studies are needed to determine proper patient selection and the long-term efficacy of neurostimulation for DED.