Vitamin abnormalities in neuropathic corneal pain

Neuropathic corneal pain (NCP) refers to spontaneous corneal pain in the absence of stimuli arising from corneal nerve dysfunction with no clinically observable ocular surface abnormalities. It is debilitating with difficult-to-manage symptoms-burning pain, photophobia, and irritation being profound. However, evidence-based clinical recommendations for the management of NCP remain scarce. Given the established role of vitamins in various neuropathies and associations between vitamin deficiencies and NCP in the literature, vitamin supplementation represents a potential therapeutic avenue that has yet to be adequately investigated in the context of NCP. This narrative review provides an overview of the therapeutic potential of vitamins B3, B12 and D as treatment in NCP, drawing evidence from both preclinical animal and clinical studies. It discusses the potential mechanisms of action rendered by various vitamins in alleviating NCP and includes the suppression of inflammation, neuroinflammation, mitochondrial dysfunction, oxidative stress, as well as the modulation of neurodegeneration and nociception dysregulation. Furthermore, we offer insight on future directions needed for vitamin supplementation to serve as mainstream treatment for NCP. Future research should also aim to establish optimal treatment protocols, including dosing regimens, treatment duration and administration methods for each vitamin.