Abstract
Purpose :
Electro-neural stimulation enhances tear secretion to treat dry eye disease. We evaluated the effects of electrical stimulation of the anterior ethmoid nerve (using a chronically implanted neurostimulator) on secretion of the tear aqueous, lipid and protein content.
Methods :
Neurostimulators were implanted beneath the nasal mucosa in New Zealand white rabbits. Stimulations (2.3-2.8mA pulses of 75-875μs in duration repeated at 30-100Hz for 3 minutes) were performed daily, for three weeks to measure changes in tear volume (Schirmer test), osmolarity (TearLab® osmometer), lipid (Oil-Red-O staining) and protein (BCA assay, mass-spectrometry).
Results :
Stimulation of the anterior ethmoid nerve in the frequency range of 30-100Hz increased tear volume by 92-133%. Modulating the treatment with 50% duty cycle (3 seconds of stimulation repeated every 6 seconds) increased tear secretion an additional 23% above continuous stimulation. Tear secretion returned to baseline levels within several minutes of stimulation. Tear film osmolarity decreased by 7mOsmol/L, tear lipid increased by 24-36% and protein concentration increased by 48%. Relative abundance of most lacrimal gland proteins (i.e. lipophilin, lipocalin, prolactin-induced protein) remained the same, while several serum (i.e. serum albumin, IgG) and corneal (i.e. cytoplasmic-1 actin, transketolase, alpha-enolase and L-lactate dehydrogenase) proteins decreased with stimulation.
Conclusions :
Electrical stimulation of the anterior ethmoid nerve increased aqueous tear volume, reduced tear osmolarity, added lipid and increased the concentration of normal tear proteins. Human studies with an intranasal stimulator should verify these results in patients with aqueous- and lipid-deficient forms of dry eye disease.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.