Melatonin for Eye Health

Research suggests a meaningful biological connection between melatonin and eye health, particularly through the retina's own capacity to produce melatonin and through specialized light-sensing retinal cells called melanopsin-expressing intrinsically photosensitive retinal ganglion cells, which help regulate circadian timing and appear to influence sleep quality when their function is compromised, as seen in Parkinson's disease. Studies indicate that the retina actively synthesizes melatonin via the enzyme HIOMT, though at levels far lower than the pineal gland, and that this local production responds dynamically to light exposure, pointing to a role for melatonin in retinal physiology beyond its well-known sleep functions. The available evidence is largely observational and mechanistic in nature, drawn from animal studies, human pupillometry research, and disease-specific investigations rather than randomized controlled trials directly testing melatonin supplementation for eye health outcomes. Taken together, the findings are directionally supportive of a relationship between melatonin, retinal cell function, and light sensitivity, but the evidence base remains preliminary and does not yet establish clear clinical applications, leaving open important questions about whether interventions targeting melatonin or melanopsin pathways could meaningfully protect or improve eye health in humans.