Neurostimulation could be the “next big thing” in dry eye disease (DED). A new neurostimulation device called TrueTear (Allergan) is a patient-directed, non-pharmacologic option.
TrueTear is inserted into the nostril; two prongs contact the ophthalmic branch of the trigeminal nerve. An electrical signal from the device signals the trigeminal nerve (5V1) and travels to cranial nerve VII, which stimulates the lacrimal glands. The nervous pathway, not reflect tears, ultimately drives secretion of basal tears.
Optometrists have questions about how the device works, patient use, and safety concerns. Let’s answer them.
What is neurostimulation?
Much like the word implies, neurostimulation describes supplying stimulation to a nerve. Neurostimulation in used in several applications in medicine, including pain management, treatment of post-traumatic stress disorder, and cognitive neurologic conditions, such as Alzheimer disease.
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As it pertains to the treatment of DED, neurostimulation using the TrueTear device initiates an afferent signaling pathway that culminates in secretion of tears by one or more proposed mechanisms.
For instance, the electrical signal received by the ethmoidal nerve may travel through the trigeminal afferent nerve fibers in the nasal cavity to the superior salivatory nucleus region of the brain, the area that controls tears.1
A second theoretical mechanism is TrueTear may induce changes in the meibomian glands that restore their ability to contribute to tears.2
Researchers have also described a pathway through which TrueTear prompts activity in glands responsible for secretion of lipids and proteins that contribute to tear development.3
TrueTear may also induce the nasal-ocular tear reflex—the stimuli might initiate a secondary signaling pathway to the pterygopalatine ganglion, a parasympathetic ganglion that has axonal projection to the lacrimal glands and nasal mucosa, which then shifts to the parasympathetic pathway to stimulate facial nerve VII, which connects to the goblet cells and meibomian glands.4