Retinal ischemia/reperfusion injury (IRI) is a common clinical condition that occurs in a variety of ocular diseases, including diabetic retinopathy [1], retinal vascular occlusion [2], anterior optic neuropathy [3], and glaucoma [4,5]. It ultimately leads to retinal ganglion cell (RGC) death because these cells are particularly vulnerable to ischemia [6,7].

Ohsawa et al. (2007) reported that molecular hydrogen (H₂) is an efficient antioxidant when administered by gaseous rapid diffusion into tissues and cells [8]. H₂, as a novel neuroprotective gas, was confirmed in a variety of ocular disease models, including optic nerve crush, diabetic retinopathy, photochemical retinal injury and retinal IRI [[9], [10], [11], [12]]. Intraperitoneal injection or ocular instillation with H₂-rich saline is the most common method of H₂ delivery. Therefore, we have developed a simple and effective method to produce the mixed gas with high-concentration H₂ for therapeutic inhalation. Moreover, the previous method of preconditioning which have been highly used was limited to its transferability, feasibility and validity into clinical applications, since patients usually receive medical treatment after IRI and the onset of retinal ischemia is unpredictable while the onset of reperfusion is predicable [13,14]. So our last study which have published on the journal of Brain Research in 2015 have firstly shown that postconditioning with inhaled hydrogen (HPC) can protect RGCs against IRI [15]. This is the first report to show that H₂ can be administrated through inhalation, which is a portable, easily administered, safe and more efficient means of delivering H₂. But the potential mechanism of protection is not clear.

Full Clinical Study: DOI: 10.1016/j.bbrc.2017.12.146