Nerve stimulation as a treatment for dry eye disease

Topical medications can be of limited efficacy. Chronic nerve stimulation of the lacrimal gland can be a better treatment option.

woman administering drops

If you have severe dry eyes that require frequent drops for symptomatic relief, lacrimal nerve stimulation may be an option for you.

Dry eye disease (DED) is one of the leading causes of eye discomfort and decreased vision. Patients often complain of a gritty or itchy sensation in the eyes and visual disturbances (e.g. temporary clouding of vision, light sensitivity). It is thought that the instability of the tear film in DED is immune-mediated and is influenced by a neural reflex loop, with the afferent and efferent branches passing through the anterior ethmoidal nerve (AEN) and lacrimal nerves, respectively.

Artificial tears and lubricating ointments, which are first-line options in the management of DED, only provide temporary relief. Topical immunomodulatory preparations such as cyclosporine and lifitegrast offer some anti-inflammatory effect, but the use of these medications is hindered by inadequate treatment response and side effects (e.g. burning sensation, unpleasant taste).

Previous pre-clinical and clinical studies have shown that electrical stimulation of the nerves innervating the lacrimal gland results in increased tear production. The objective of this study, therefore, was to evaluate the safety and efficacy of chronic electric stimulation of the AEN and LN via surgically-placed implants.

Experimental rabbits were assigned to either the AEN or LN treatment groups. The neuroimplants were designed to consist of a gold coil, a platinum black electrode, and platinum cured silicone. These were surgically placed either beneath the lacrimal gland and adjacent to the LN or along the dorsal rim of the nasal septum. Electrical stimulations were done 4-7 days after implantation, with the pulse duration dependent on rabbit response. As control, the other eye was treated with sham electrical pulses.

Using the Schirmer test, tear volume was observed to be increased by 32% (versus sham) in rabbits who received LN stimulation. Meanwhile, AEN stimulation resulted in a 133% in the stimulated eye and 64% increase in the fellow eye. Histopathologic examination of the lacrimal gland after 4-7 months of electric stimulation showed no evidence of damage, indicating that the implant was tolerated well. However, the nasal septum showed mucosal thinning, fibrosis and inflammation.

This research has shown that AEN stimulation is significantly more effective than LN stimulation in increasing bilateral tear production. However, further optimization of the nasal implants is necessary. The use of chronic nerve stimulation can be of benefit to patients with severe DED, although it is not likely to work in patients who already have a normal tear volume or have aberrant innervations to the lacrimal gland.

Kossler, A., Brinton, M., Patel, Z., Dalal, R., Ta, C., & Palanker, D. (2019). Chronic Electrical Stimulation for Tear Secretion: Lacrimal vs. anterior ethmoid nerve. The Ocular Surface. doi: 10.1016/j.jtos.2019.08.012

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