Intranasal Tear Neurostimulation: An Emerging Concept in the Treatment of Dry Eye
DED is mainly characterized by an unstable tear film and a variety of ocular irritation or vision-related symptoms, including foreign body sensation, burning, photophobia, conjunctival hyperemia, ocular fatigue, and fluctuating visual disturbances. It is potentially accompanied by ocular surface damage in chronic disease.1,5 Despite numerous research studies, the pathogenesis of DED is not completely understood. However, most studies have documented that inflammation in the lacrimal functional unit (LFU) has a prominent role in the pathogenesis and progression of the disease.6–9 Furthermore, therapies targeting these disease-relevant inflammatory mediators are beginning to emerge9 and anti-inflammatory treatment has become standard in the management of DED.6 In addition, lubricating the ocular surface with artificial tears remains the mainstay of therapy.10 The pharmaceutical and biotechnological industries have provided new molecules (trehalose) and combinations (hyaluronic acid and carboxymethylcellulose) for use in artificial tears, enabling clinicians to more effectively treat dry eye patients.11–13 However, despite these advances, the use of artificial tears has obvious limitations. In addition to their temporary relief, necessitating frequent instillation, artificial tears cannot completely substitute the complex composition of natural tears. Thus, novel therapeutic agents and treatment modalities that stimulate tearing are necessary to achieve better clinical outcomes in dry eye patients.
Recently, one of the most promising innovative treatment modalities for dry eye is the use of neurostimulation/neuromodulation that has been successfully used for a variety of different medical indications.14–16 The aim of this review article is to discuss intranasal lacrimal neurostimulation in some detail, including its history, mechanism, and clinical results.