Eye health has acquired a distinctly digital vocabulary. Screen time, blue-light glasses, dark mode, artificial tears, and reminders to look into the distance have become familiar parts of the conversation about protecting our eyes. That concern has emerged alongside a profound change in how much of daily life occurs through digital devices. In the United States, smartphone ownership increased from 35% of adults in 2011 to 91% in 2025, while 46% of teenagers reported being online almost constantly in 2024, nearly twice the proportion recorded a decade earlier. Furthermore, a systematic review of 103 studies involving 66,577 participants estimated the pooled prevalence of computer vision syndrome, or digital eye strain, at 69%.
The changes extend beyond eyes that feel tired or dry after a day in front of a screen. Myopia has become increasingly common among children and adolescents worldwide. A 2025 systematic review and meta-analysis of 276 studies representing more than 5.4 million participants estimated that pooled myopia prevalence increased from 24.3% in 1990 to 35.8% in 2023 and projected that it could reach 39.8% by 2050, affecting more than 740 million young people. Myopia has genetic and environmental determinants, and recent evidence continues to associate greater near-work exposure with higher myopia risk in children, while greater time outdoors is associated with a lower risk of developing myopia.
A different pressure is building later in life. Between 1990 and 2020, the number of people aged 50 years or older who were blind increased by about 51% worldwide, while the number living with moderate or severe vision impairment increased by about 92%, even as the age-standardized prevalence of blindness declined. By 2050, the same analysis projected approximately 61 million people living with blindness and 474 million with moderate or severe vision impairment, driven in large part by population growth and aging. Age-related macular degeneration illustrates that demographic effect particularly clearly: the number of people with AMD-related vision impairment rose from 3.64 million in 1990 to 8.06 million in 2021 even though the age-standardized prevalence rate declined by about 5.5% over the same period.
Metabolic disease adds another layer to the same story. Among working-age adults, the global prevalence rate of vision impairment caused by diabetic retinopathy increased significantly between 1990 and 2021, with an estimated 2.85 million affected people in 2021, or about 2.8 times the number in 1990. Taken together, these trends describe more than a rise in any one eye disorder. The visual system is being challenged across the lifespan: by changing visual environments early in life, by decades of continued function, by aging, and by the vascular and metabolic consequences of diseases such as diabetes.
The biology of vision helps explain why those very different pressures can eventually converge on some of the same vulnerabilities. The retina is among the most metabolically active tissues in the body, with exceptionally high oxygen demand and a tightly regulated vascular supply. Photoreceptor membranes are rich in polyunsaturated fatty acids that are essential for their structure and function but are also susceptible to oxidation, while the retina is continuously exposed to visible light and a highly oxygenated environment. Photoreceptors also continually renew their outer segments, creating substantial demand for glucose metabolism, biosynthesis, and reducing power to protect cellular components from oxidative damage.
That workload depends on balance. Reactive oxygen species (ROS) participate in normal cellular signaling, while antioxidant and repair systems continuously prevent normal oxidative metabolism from becoming damaging. Even so, aging can weaken those protective and reparative systems and allow oxidative damage to accumulate. Across retinal and optic-nerve diseases, redox imbalance can intersect with mitochondrial dysfunction, inflammatory signaling, vascular abnormalities, and pathways that determine whether stressed cells recover or die. These mechanisms appear in different combinations in age-related macular degeneration, diabetic retinopathy, glaucoma, retinal ischemia, and other forms of ocular injury, giving very different diseases some overlapping biological vulnerabilities. The common thread is therefore not simply “oxidative stress,” but what happens when the eye becomes less able to control the downstream consequences of that stress: impaired energy production, inflammatory activation, abnormal vascular responses, and progressive loss of cells that cannot readily be replaced.
Molecular hydrogen (H₂) has entered ophthalmic research at several points within that cascade. One of the earliest studies used hydrogen-loaded eye drops in a rat model of retinal ischemia-reperfusion injury and found that H₂ rapidly reached the vitreous, reduced hydroxyl-radical levels and markers of oxidative damage and apoptosis, and limited subsequent retinal thinning. That finding established two important points for later research: molecular hydrogen could reach tissue inside the eye, and reducing the oxidative burst produced during acute retinal injury could preserve retinal structure.
Later experiments suggest a broader mechanism than direct radical scavenging alone. In retinal tissue exposed to nitrative stress, H₂ reduced protein nitration, preserved mitochondrial membrane potential, suppressed apoptosis, and limited neuronal loss. In rats exposed to intense light, hydrogen-rich saline increased SIRT1 expression and endogenous antioxidant activity while reducing lipid peroxidation and activation of apoptotic proteins, while blocking SIRT1 weakened the protective effect. A separate study found that H₂ preserved SIRT3, a mitochondrial stress-response protein, while reducing ROS, oxidative DNA damage, inflammatory NF-κB signaling, and markers of cellular senescence.
These findings begin to explain why H₂ is being investigated across eye disorders that otherwise have very different causes. Excess reactive species can damage membranes and DNA, disrupt mitochondria, amplify inflammation, and activate pathways that push stressed retinal cells toward senescence or apoptosis. H₂ has affected several points along that progression, including nitrative damage, mitochondrial stability, endogenous antioxidant defenses, inflammatory signaling, and the molecular machinery governing cell survival. Its potential relevance therefore lies less in eliminating ROS than in influencing whether oxidative pressure remains manageable or progresses into dysfunction and cell loss.
The vascular research adds another important dimension. In diabetic mice, long-term hydrogen-rich water improved abnormal retinal blood-flow responses to visual stimulation and systemic hyperoxia while reducing retinal nitrative stress and gliosis, suggesting improved neurovascular coupling, the coordination between neural activity and the blood supply needed to support it. That connection is particularly important in diabetic retinopathy, where the problem extends beyond damage inside individual retinal cells to disruption of the relationship among neurons, glial cells, and the microvasculature responsible for meeting their metabolic needs.
H₂ has also been studied where abnormal vascular growth becomes part of the disease process. In a mouse model of choroidal neovascularization associated with neovascular age-related macular degeneration, hydrogen inhalation reduced vascular leakage while suppressing HIF-1α, VEGF, TNF-α, and IL-6, linking H₂ to hypoxic, angiogenic, and inflammatory signaling within the same injury response. A 2024 oxygen-induced retinopathy study similarly found that H₂ promoted normal retinal revascularization while reducing pathological neovascularization, vascular leakage, and microglial activation, with Nrf2, Dll4/Notch, and HIF-1α/VEGF signaling implicated in the response. These findings are notable because healthy retinal function depends on preserving an adequate vascular supply without allowing the uncontrolled, leaky vessel growth that can itself damage vision.
The same pattern extends to retinal degeneration. In rd6 mice, a genetic model of progressive photoreceptor degeneration, long-term hydrogen-water consumption slowed retinal thinning, preserved photoreceptors and retinal electrical responses, and altered expression of genes involved in phototransduction. Other degeneration models have likewise reported reduced lipid peroxidation, apoptosis, and microglial activation alongside stronger antioxidant and SIRT-related responses. Across these models, the recurring outcome is preservation of retinal cells and function when the tissue is placed under conditions that would otherwise drive progressive degeneration.
Some of that research has now reached humans. In a prospective randomized double-masked trial involving 32 patients undergoing cataract surgery in both eyes, hydrogen dissolved in the surgical irrigation solution reduced corneal endothelial-cell loss: three weeks after surgery, endothelial-cell density had fallen by 18.4% with conventional irrigation compared with 8.5% when H₂ was used. The study is particularly useful because the oxidative insult occurs during the procedure itself, allowing H₂ to be delivered directly into the environment in which corneal endothelial injury is developing. It therefore provides a relatively direct human test of the tissue-protection hypothesis suggested by the preclinical work. A separate randomized crossover study in 10 adults found that a persistent H₂-generating supplement improved tear stability and several dry-eye symptoms, with accompanying mouse experiments showing increased tear secretion and protection of lacrimal-gland function under dry-eye stress. Together, these studies suggest that H₂ may be relevant wherever oxidative or inflammatory stress compromises specialized ocular tissues.
The human evidence remains small, and molecular hydrogen cannot currently be treated as an established therapy for common eye diseases. Most of the detailed mechanistic evidence still comes from animal or cellular models, and the route, dose, timing, and duration of H₂ exposure differ considerably among studies. The mechanistic evidence nevertheless helps explain why H₂ continues to appear in studies of conditions that otherwise look unrelated. Different ocular disorders place different pressures on the visual system, yet many eventually converge on mitochondrial function, oxidative and inflammatory control, vascular regulation, and the decision of stressed cells to recover or die. For a visual system required to perform metabolically demanding work for a lifetime, preserving that cellular environment may be as important as responding to damage after vision has already begun to decline.
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