Neurostimulation in dry eye disease-past, present, and future

Neuromodulation is a novel approach that utilizes electrical signals, pharmaceutical agents, or other forms of energy to modulate abnormal neural function through neurostimulation. Neurostimulation is a novel technique that uses electrical currents to stimulate the nervous system. During the recent few decades, neuromodulation has gained significant attention, in particular for the treatment of chronic neurological diseases, due to its success in treating patients unresponsive to conventional pharmacological therapies. Dry eye disease (DED) is a chronic, multifactorial disease that affects millions of people worldwide. Recent data have demonstrated that neurosensory abnormalities contribute to the pathogenesis of DED. Current mainstays of dry eye therapy include lubrication, tear retention, and anti-inflammatory therapies, among others. The recent development of intranasal neurostimulation therapy for DED utilizes the nasolacrimal reflex as an alternative pathway, not only to increase tear production via increased lacrimation, but also to target other tear film components, such as mucin and meibum secretion, promoting tear film homeostasis. This review aims to describe the different types of neuromodulation devices available and their application for non-ocular diseases, as well as to review recent advances and literature on ocular neurostimulation.