Novel Role of Molecular Hydrogen: The End of Ophthalmic Diseases?

Molecular hydrogen (H₂) is a colorless, odorless, and tasteless gas which displays non-toxic features at high concentrations. H₂ can alleviate oxidative damage, reduce inflammatory reactions and inhibit apoptosis cascades, thereby inducing protective and repairing effects on cells. H₂ can be transported into the body in the form of H₂ gas, hydrogen-rich water (HRW), hydrogen-rich saline (HRS) or H₂ produced by intestinal bacteria. Accumulating evidence suggest that H₂ is protective against multiple ophthalmic diseases, including cataracts, dry eye disease, diabetic retinopathy (DR) and other fields. In particular, H₂ has been tested in the treatment of dry eye disease and corneal endothelial injury in clinical practice. This medical gas has brought hope to patients suffering from blindness. Although H₂ has demonstrated promising therapeutic potentials and broad application prospects, further large-scale studies involving more patients are still needed to determine its optimal application mode and dosage. In this paper, we have reviewed the basic characteristics of H₂, and its therapeutic effects in ophthalmic diseases. We also focus on the latest progress in the administration approaches and mechanisms underlying these benefits.