Dry eye syndrome may soon be treated with a new implant developed by a team led by researchers at Stanford University. The team identified the afferent neural pathway as being an excellent target for stimulation in order to activate tear production. They built a device that has platinum foil electrodes implanted under the inferior lacrimal gland, with an additional electrode reaching for the afferent ethmoid nerve. A remote control was used to activate the electric stimulation. The study was conducted with laboratory rabbits, some of which had long term wireless stimulators implanted to provide power.
The researchers were able to produce substantial increase in tear production compared to controls and work is now underway to move toward FDA clinical trials on human patients.
Summary of the results of using the implants according to the study abstract in Journal of Neural Engineering:
Stimulation of the lacrimal gland increased tear secretion by engaging efferent parasympathetic nerves. Tearing increased with stimulation amplitude, pulse duration and repetition rate, up to 70 Hz. Stimulation with 3 mA, 500 μs pulses at 70 Hz provided a 4.5 mm (125%) increase in Schirmer score. Modulating duty cycle further increased tearing up to 57%, compared to continuous stimulation in chronically implanted animals (36%). Ethmoid (afferent) nerve stimulation increased tearing similar to gland stimulation (3.6 mm) via a reflex pathway. In animals with chronically implanted stimulators, a nearly 6 mm increase (57%) was achieved with 12-fold less charge density per pulse (0.06–0.3 μC mm−2 with 170–680 μs pulses) than the damage threshold (3.5 μC mm−2 with 1 ms pulses).
Study in Journal of Neural Engineering: Electronic enhancement of tear secretion…
Source: Institute of Physics…
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