Glaucoma: A Nutrition and Natural-Health Reference
Definition and Overview
The glaucomas are a group of progressive optic neuropathies characterized by degeneration of retinal ganglion cells and resulting changes in the optic nerve head. This condition results in a characteristic optic nerve head appearance and a corresponding progressive loss of vision. Glaucoma can be categorized into either primary or secondary types, and further into open-angle or closed-angle variants within each type.
Glaucoma is the leading cause of irreversible blindness worldwide, currently estimated to affect 76 million individuals aged 40β80 years, with projections rising to 112 million by 2040. Due to the insidious onset and low detection rate in the early stages of glaucoma, most patients are diagnosed in advanced stages with extensive and irreversible damage.
Classification of Glaucoma
Adult glaucoma includes primary open-angle glaucoma (POAG) and angle-closure glaucoma, as well as secondary open and angle-closure glaucoma, with POAG being the most prevalent type.
- Primary Open-Angle Glaucoma (POAG): POAG is described distinctly as a multifactorial optic neuropathy that is chronic, progressive, and irreversible, with a characteristic acquired loss of optic nerve fibers. Patients with POAG are often asymptomatic until significant optic nerve damage occurs, unless early signs of glaucoma are identified during routine eye examinations.
- Acute Angle-Closure Glaucoma: Acute angle-closure glaucoma can develop suddenly and lead to a rapid decline in vision, accompanied by symptoms such as corneal edema, eye pain, headache, nausea, and emesis.
- Secondary Glaucoma: Secondary glaucoma often arises due to a previous eye injury or underlying medical conditions, resulting in elevated IOP and subsequent optic neuropathy. This category encompasses various subtypes, including congenital, pigmentary, neovascular, exfoliative, traumatic, and uveitic glaucoma.
- Normal-Tension Glaucoma: Glaucomatous changes in the optic nerve may arise even when intraocular pressure is within normal limits. Among persons of European ancestry, the intraocular pressure is normal in 30% of all cases of glaucoma. This disorder is apparently caused by an intraocular pressure that, although within normal limits, nonetheless exceeds the pressure sensitivity of the optic disc.
Body Systems and Anatomical Structures Involved
The Optic Nerve and Retinal Ganglion Cells
The optic disc is composed of neural, vascular, and connective tissues. The convergence of the axons of retinal ganglion cells at the optic disc creates the neuroretinal rim; the rim surrounds the cup, a central shallow depression in the optic disc. Retinal ganglion cell axons exit the eye through the lamina cribrosa, forming the optic nerve, and travel to the lateral geniculate nucleus, the thalamic relay nuclei for vision.
Glaucomatous optic neuropathy involves damage and remodeling of the optic disc tissues and lamina cribrosa that lead to vision loss. With elevated intraocular pressure, the lamina cribrosa is posteriorly displaced and thinned, leading to deepening of the cup and narrowing of the rim.
Aqueous Humor Dynamics and the Trabecular Meshwork
The front part of the eye is filled with a clear fluid called aqueous humor, produced by the ciliary body. This fluid leaves the eye through channels in the anterior chamber angle. Anything that slows or blocks the flow of this fluid out of the eye will cause pressure to build up in the eye.
High IOP usually occurs as a result of an increase in aqueous humor outflow resistance at the trabecular meshwork (TM). An abnormal TM contributes to the development of glaucoma. Oxidative stress and vascular damage are considered two major cellular factors that lead to alterations in the TM.
Oxidative Stress in the Trabecular Meshwork
Oxidative stress-induced dysfunction of trabecular meshwork cells can obstruct the outflow of aqueous humor, leading to pathologically high IOP and contributing to glaucoma. Glaucoma is an age-dependent disease closely related to oxidative stress. Oxidative stress marker levels are significantly increased in the aqueous humor of glaucoma patients, suggesting that outflow tissues, including the TM, in glaucomatous eyes are continuously exposed to oxidative stress. Oxidative DNA damage is also significantly increased in the TM of glaucoma patients.
The pathogenic role of reactive oxygen species (ROS) in glaucoma is supported by findings that resistance to aqueous humor outflow is increased by hydrogen peroxide through TM degeneration; TM possesses remarkable antioxidant activities, mainly related to superoxide dismutase-catalase and glutathione pathways, that are altered in glaucoma patients; and intraocular pressure increase and severity of visual field defects in glaucoma patients parallel the amount of oxidative DNA damage affecting the TM.
Mitochondrial and Metabolic Dysfunction
Accumulating research emphasizes the metabolic susceptibility of retinal ganglion cells, specifically concerning the progressive depletion of nicotinamide adenine dinucleotide (NAD+), a pivotal coenzyme fundamental to mitochondrial energy production and cellular survival mechanisms. As a key biosynthetic precursor in NAD+ synthesis pathways, nicotinamide (NAM), a form of vitamin B3, has exhibited significant neuroprotective properties across various preclinical experimental models and preliminary clinical investigations.
Although lowering intraocular pressure is the only proven prevention and therapy, multiple interrelated mechanisms, including vascular dysregulation, oxidative stress, immune-inflammatory activation, excitotoxicity, and mitochondrial dysfunction, are implicated in RGC injury.
Contributing and Associated Risk Factors
Established Risk Factors
Six risk factors for POAG have been identified in systematic review and meta-analysis, including IOP treatment (meta-OR = 3.69), family history of glaucoma (meta-OR = 2.49), myopia (meta-OR = 2.08), elevated IOP (meta-OR = 1.13), advanced age (meta-OR = 1.07), and male sex.
Risk factors consistently associated with the development of open-angle glaucoma in individuals with healthy eyes include older age and an approximately 1 mm Hg increase in intraocular pressure at baseline. Predictive factors for development of open-angle glaucoma in individuals with ocular hypertension include older age, thinner central corneal thickness, higher cup-to-disk ratios of the optic disc, and higher pattern standard deviation values on automated perimetry at baseline.
Vascular and Systemic Factors
Several epidemiological studies confirmed the importance of vascular risk factors, particularly hypertension and blood pressure dipping, in the pathogenesis and progression of glaucomatous optic neuropathy. Diabetes mellitus is associated with elevated intraocular pressure, but has no clear association with POAG.
Factors like elevated IOP and vascular dysregulation primarily contribute to the initial insult during glaucomatous atrophy in the form of obstruction to axoplasmic flow within the RGC axons at the lamina cribrosa, altered optic nerve microcirculation at the level of the lamina, and changes in the laminar glial and connective tissue.
Genetic and Environmental Interaction
Hypothesis-free genome-wide association studies have furthered understanding of the complex genetic architecture underpinning glaucoma, while epidemiological studies have provided advances in the identification of environmental risk factors. It is increasingly recognized that the combined effects of genetic and environmental factors may confer a disease risk that departs from a simple additive effect of the two.
People over 60 years of age, family members of those already diagnosed with glaucoma, steroid users, diabetics, those with high myopia, hypertension, central cornea thickness below 5 mm, and eye injury are at an increased risk of glaucoma.
The Role of Oxidative Stress and Nutrition: Biological Rationale
Oxidative stress results from an imbalance between the production of reactive oxygen species and the capacity of antioxidants and repair systems, leading to damage to lipids, proteins, and DNA structures, and subsequently to cellular destruction. Deficiencies or over-supplementation of certain macro- and micronutrients also adversely affect the course of glaucomatous neuropathy. Given the multifactorial nature of glaucoma and its chronic course, the role of nutrition and appropriate choice of dietary nutrients should be considered as an adjunct to treatment or to inhibit disease progression.
Dietary antioxidants (e.g., carotenoids, vitamins C and E, and polyphenols) and one-carbon-pathway nutrients (e.g., folate and vitamins B-2/B-6/B-12) support glutathione regeneration and homocysteine control, thereby mitigating oxidative and nitrosative stress implicated in RGC injury.
Nutrients and Natural Ingredients Studied in Relation to Glaucoma
Key nutrients studied specifically in the context of glaucoma include the herbs ginkgo biloba and ginseng; catechins in green tea (epigallocatechin gallate [EGCG]) and cocoa beans; black currant and bilberry anthocyanins; carotenoids in saffron and lutein, zeaxanthin, and meso-zeaxanthin; forskolin; rutin; alpha-lipoic acid (ALA); vitamins A, B, C, and E; omega-3 essential fatty acids; citicoline; palmitoylethanolamide (PEA); homotaurine; carnosine; and trace elements zinc, copper, magnesium, and manganese.
Vitamin C (Ascorbic Acid)
Scientific evidence: In a study looking at the prevalence of glaucoma and dietary supplement use among participants of the National Health and Nutrition Examination Survey, supplemental intake of vitamin C was linked to a decreased chance of glaucoma; however, this did not correlate with serum vitamin C levels. No relation was found between reported glaucoma and supplemental use, or serum levels, of vitamins A and E.
Vitamins A, E, and Carotenoids (Beta-Carotene, Retinol)
Scientific evidence: Participants diagnosed with glaucoma consumed a diet with a lower intake of antioxidant-rich foods, such as Ξ²-carotene, retinol, and B vitamins (B1 and B12), and a higher intake of magnesium- and vitamin E-rich foods than participants without glaucoma, based on the prospective Rotterdam study cohort of more than 3,500 participants. Coleman et al. found a decreased glaucoma risk in women who consumed fruits and vegetables rich in vitamin A and carotenes, namely collard greens, kale, carrots, and peaches. Evidence for individual vitamin supplementation in glaucoma remains weak and mostly observational.
B Vitamins (Including Nicotinamide / Vitamin B3)
Scientific evidence (Nicotinamide): The current research landscape indicates that B vitamins, particularly vitamin B3 (nicotinamide), represent the most advanced area of vitamin research in glaucoma, with multiple Phase II and III clinical trials ongoing worldwide.
A randomized crossover clinical trial showed that oral nicotinamide supplementation enhanced RGC function, as assessed by electroretinography, regardless of IOP levels. A 12-week crossover randomized clinical trial in Australia of 57 participants found improved inner retinal function as assessed by electroretinography with nicotinamide supplementation of 3 g/day.
The Glaucoma Nicotinamide Trial is a prospective, randomized, placebo-controlled double-masked clinical trial. It has two arms: the Swedish Glaucoma Nicotinamide Trial and the vitamin B3 in glaucoma study. The results of large-scale clinical trials are still awaited before NAD can be considered an accepted therapeutic modality for glaucoma.
Nicotinamide has a simple chemical structure that allows it to serve as a precursor to nicotinamide adenine dinucleotide (NAD), a vital coenzyme in cellular metabolic processes. NAD is essential for mitochondrial function, as it supports oxidative phosphorylation and ATP production, which are critical for maintaining neuronal health and energy homeostasis.
Vitamin combinations targeting metabolic dysfunction in retinal ganglion cells appear more promising than single-vitamin approaches; however, few studies have been performed with proper single-compound-only controls, which makes scientific interpretation more difficult.
Omega-3 Fatty Acids (DHA and EPA)
Scientific evidence: The effect of polyunsaturated fats on glaucoma remains inconsistent and warrants source- (plant vs. animal) and substitution-based analyses.
A prospective randomized study evaluated the effect of citicoline, vitamin C, and docosahexaenoic acid (DHA) in patients with glaucoma. Patients were randomized to treatment with vitamin C, DHA, citicoline, or a combination of DHA and citicoline for 3 months. Mean defect significantly improved (p = 0.001) from β9.52 to β7.85 dB during the study period in persons taking DHA + citicoline. Similarly, the mean visual field index significantly improved in this group. This was a short-duration study with a small sample and must be considered preliminary.
Flavonoids and Anthocyanins
Scientific evidence: Studies suggest that flavonoids exert a beneficial effect in glaucoma, particularly in terms of improving ocular blood flow and potentially slowing progression of visual field loss.
A study was performed to evaluate the effect of ginkgo biloba extract (GBE) and anthocyanins on visual function in patients with normal tension glaucoma based on the vascular theory of glaucomatous optic nerve damage. Retrospective analysis was carried out by a chart review of 332 subjects who were treated with anthocyanins, GBE, or no medication. Flavonoids (anthocyanins and flavanols), carotenoids (lutein/zeaxanthin), and B vitamins have strong biological rationale for glaucoma prevention but have limited support from long-term, large population-based studies.
Ginkgo Biloba
Traditional use: Ginkgo biloba (Ginkgo biloba L.) leaf extract has been used for centuries in traditional Chinese medicine for circulatory and cognitive conditions. The standardized extract (EGb 761) is prepared from dried leaves.
Scientific evidence: In addition to its antioxidative and anti-inflammatory properties, GBE has been shown to improve endothelium-dependent vasodilation, thereby increasing microcirculation and reversing vasospasms. GBE also stabilizes the inner mitochondrial membrane and increases the membrane potential, which restores the respiratory chain and increases ATP production.
GBE appears to increase ocular blood flow in those with glaucoma. However, data on visual field outcomes are inconclusive.
A 2025 systematic review retrieved data from 8 studies including 428 patients, with a median follow-up of 3.7 months. The administration of GBE was not associated with an improvement in IOP, mean deviation, corrected pattern standard deviation, or heart rate from baseline to the last follow-up.
In previous studies, GBE has been shown to slow the progression of visual field damage and improve visual function in normal tension glaucoma patients. However, to date, conclusive evidence of the efficacy of GBE on IOP, mean deviation, and visual field testing is lacking. GBE holds promise as a neuroprotective treatment for glaucoma, but larger, well-designed clinical trials are needed to validate its effectiveness and determine its place in clinical practice.
Bilberry (Vaccinium myrtillus) and Anthocyanins
Traditional use: Bilberry has been used in European herbal medicine for centuries, primarily for eye health and circulatory support, with preparations from the ripe berries used to improve night vision and reduce eye fatigue.
Scientific evidence: A combination of ginkgo biloba and anthocyanins from Vaccinium myrtillus (bilberry) achieved a significant improvement in Humphrey visual field parameters and also reported significant improvement in best corrected visual acuity after two years of oral supplementation. This study was retrospective in design, which limits causal inference. Overall, the evidence base for bilberry alone in glaucoma is limited to preliminary and observational data.
Citicoline (CDP-Choline)
Scientific evidence: Citicoline has demonstrated neuroprotective properties in central neurodegenerative diseases. However, conclusive evidence of the effect of citicoline on glaucoma progression is missing. Experimental studies on retinal cell cultures and animal models showed a protective effect of citicoline on glaucomatous damaged RGC.
Citicoline, also known as cytidine 5β²-diphosphocholine, a naturally occurring compound, has garnered attention for its potential neuroprotective effects in the context of glaucoma. Although initial preclinical and early clinical studies have shown promising outcomes, larger and more thorough trials are necessary to validate its effectiveness and define its place in clinical practice.
Resveratrol and Green Tea Catechins (EGCG)
Scientific evidence: The most compelling evidence in nutraceutical research for glaucoma exists for nicotinamide, homotaurine, resveratrol, and melatonin, whilst emerging compounds like vitamin K1 are under investigation. Other neuroprotective candidates, including coenzyme Q10 and dietary interventions like the ketogenic diet, are under investigation, though large-scale clinical evidence remains limited. Evidence for EGCG and resveratrol in human glaucoma is largely confined to cell-culture and animal studies at present.
Magnesium
Scientific evidence: Oral magnesium therapy has been studied in relation to visual field and ocular blood flow in glaucoma patients. Glaucoma patients have been observed to have a higher dietary intake of magnesium-rich foods compared to non-glaucoma participants in the Rotterdam study, though interpretation is complicated by the observational design. The overall evidence base for magnesium supplementation in glaucoma is preliminary and inconclusive.
Vitamin D
Scientific evidence: Vitamin D regulates anti-inflammatory and immunomodulatory ocular and neurological cellular processes, potentially conveying neuroprotective properties. While vitamin D supplementation has been shown to lower IOP in primate experiments, evidence for this in humans is limited and conflicting. High-quality randomized trials are needed to evaluate the efficacy of vitamin D supplementation in glaucoma neuroprotection.
Lutein and Zeaxanthin
Scientific evidence: Lutein and zeaxanthin are carotenoids concentrated in the macula and retina. They are studied in the context of glaucoma as part of broader antioxidant strategies. Analysis of the NHANES database found that higher dietary antioxidant indices were associated with lower risk of glaucoma, a composite finding that includes carotenoid-rich diets, though the cross-sectional design prevents causal conclusions. No large randomized controlled trials have specifically isolated lutein or zeaxanthin supplementation for glaucoma outcomes.
Alpha-Lipoic Acid (ALA)
Scientific evidence: Alpha-lipoic acid is included among the broader group of antioxidant compounds studied in glaucoma, listed in systematic reviews of nutritional supplementation in the condition. It is among the key nutrients studied specifically in the context of glaucoma. However, human clinical trial data for ALA specifically in glaucoma remain sparse, and existing evidence is largely preclinical.
Homotaurine
Scientific evidence: A nutraceutical formulation (Epicolin) based on citicoline, homotaurine, epigallocatechin-3-gallate, forskolin, and vitamins showed significant neuroprotective, antioxidant, and anti-inflammatory effects in both in vitro and in vivo studies. Homotaurine appears in combination formulations but has not been sufficiently studied as a standalone agent in robust human glaucoma trials.
Coenzyme Q10
Scientific evidence: Coenzyme Q10 is among the neuroprotective candidates under investigation for glaucoma, though large-scale clinical evidence remains limited. Evidence is primarily from preclinical and small human studies.
Dietary Patterns and Lifestyle Factors
Fruits, Vegetables, and Antioxidant-Rich Diets
Being rich in antioxidants, a diet rich in fruits and vegetables is speculated to decrease the risk of developing glaucoma. However, the nutrient composition of different fruits and vegetables varies, making it difficult to link any presumed protective effect to a single source. Nonetheless, multiple cross-sectional studies have been conducted using food frequency questionnaires in an attempt to link certain fruits and vegetables to glaucoma.
Mediterranean Diet
The effect of the Mediterranean lifestyle (ML) on glaucoma incidence was analyzed in the SUN Project. The SUN Healthy Lifestyle Score (SHLS) includes 10 healthy habits: never having smoked, moderate to high physical activity, Mediterranean diet adherence, moderate alcohol consumption, low television exposure, no binge drinking, short afternoon napping, meeting up with friends, working at least 40 h/wk, and low body mass index. After a median of 12 years of follow-up, 261 incident cases of glaucoma were recorded. This large prospective cohort study found an association between greater adherence to healthy lifestyle habits and lower glaucoma incidence, though the composite nature of the score limits attribution to diet alone.
Caffeine and Coffee
Coffee is a rich source of caffeine, a biologically active compound that exerts numerous physiological effects on the human body. A transient elevation in IOP has been noted following caffeine ingestion in patients with different types of glaucoma, and to a lesser extent in healthy individuals. The Blue Mountains Eye Study found a higher mean IOP among POAG patients that reported regular caffeine consumption.
The pooled evidence reveals that the effect of caffeine on IOP varies among individuals: in healthy populations, caffeine intake does not cause changes in IOP; in contrast, caffeine intake in patients with glaucoma or ocular hypertension tends to increase the IOP significantly.
Findings from large prospective cohorts suggest that high coffee consumption β β₯5 cups per day β may significantly increase glaucoma risk (Ptrend = 0.02). Similarly, UK Biobank data indicate that in individuals with a high polygenic risk score for glaucoma, heavy coffee consumption may sharply elevate disease risk. Caffeine consumption has also been linked to an increased risk of exfoliation glaucoma (XFG) but not normal tension glaucoma. This may be mechanistically plausible, as coffee intake elevates plasma and aqueous humor homocysteine levels, and hyperhomocysteinemia has been implicated in the pathogenesis of exfoliation syndrome.
Alcohol
Data from the Framingham Eye Study suggests that there is a positive association between high alcohol consumption and glaucoma. A subset of case-control studies conducted on small numbers of patients found that alcohol consumption offers a protective effect against the development of POAG and ocular hypertension. The evidence on alcohol is therefore mixed and inconsistent across study designs.
Smoking and alcohol use are frequently coupled with poorer diet quality (e.g., lower vegetable intake) and heightened oxidative stress, which may exacerbate glaucomatous neurodegeneration.
Physical Exercise
Consistent protective effects of aerobic exercise and high-quality sleep may be associated with favorable metabolic profiles and ocular perfusion, potentially mitigating retinal ganglion cell loss. Growing evidence suggests that lifestyle factors β particularly dietary patterns and specific nutrients, as well as exercise, smoking, sleep, alcohol, and caffeine β may modulate underlying pathophysiological mechanisms of glaucoma.
Ketogenic and Low-Carbohydrate Diets
An association was found between paracentral visual field loss and a low-carbohydrate, high-fat and -protein diet from vegetable sources, representing approximately a 20% reduced risk of this POAG subtype. The authors suggest this supports findings of mitochondrial and lipid metabolism dysfunction in this POAG subtype, normal-tension glaucoma, and Leber's hereditary optic neuropathy. Clinical trials employing controlled ketogenic or derivative diets will be necessary to fully assess their effects on glaucoma progression and evaluate their role as effective therapeutic strategies.
High-Salt Diet
Glaucoma is linked to a variety of factors, including elevated intraocular pressure, optic nerve damage, and oxidative stress. In recent years, dietary habits, as a controllable lifestyle factor, have received increasing attention in the prevention and management of glaucoma. Research has examined potential connections between high sodium intake and IOP elevation via effects on systemic blood pressure and fluid dynamics, but specific clinical evidence in human glaucoma remains limited.
Limitations of the Existing Evidence Base
Much of the current literature is constrained by cross-sectional designs, reliance on self-reported food frequency questionnaires, and insufficient use of structural endpoints such as retinal nerve fiber layer imaging.
To date, the only prospective randomized clinical trial evaluating the possible effect of antioxidant supplements in glaucoma was published by Garcia-Medina et al., who studied the effect of the AREDS formula on a small sample of patients with mild to moderate POAG. This illustrates how sparse the high-quality interventional evidence remains across the field.
Vitamin combinations targeting metabolic dysfunction in retinal ganglion cells appear more promising than single-vitamin approaches; however, few have been performed with proper single-compound-only controls, which makes scientific interpretation of the studies more difficult.
References
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