Magnesium and Glaucoma: What Do Human Studies Show?
Glaucoma is a chronic eye disease where the optic nerve is damaged over time, often leading to vision loss if untreated. The most common form is primary open-angle glaucoma (POAG), in which eye pressure tends to be high. A related condition, normal-tension glaucoma (NTG), causes nerve damage even though eye pressure (intraocular pressure, IOP) is not elevated. Researchers have wondered if improving ocular blood flow and nerve health could help slow glaucoma. Magnesium is a mineral that supports blood vessel function and nerve cell health (pmc.ncbi.nlm.nih.gov). This has led scientists to test if glaucoma patients might benefit from more magnesium, either by diet or supplements.
This article reviews all human studies on magnesium in glaucoma. Specifically, we look at trials and reports of magnesium levels or supplementation in POAG and NTG. We focus on study design, patient numbers, what dose of magnesium was used, how long patients were treated, and what outcomes were measured: visual field tests (checking side and central vision), OCT scans of nerve fiber thickness (RNFL) or ganglion cell layers (GCC), blood flow measures, and IOP. We also comment on study quality and differences between studies, and point out what’s still unknown.
Why Magnesium? The Rationale
Magnesium plays roles in blood vessel function and nerve protection. It can relax blood vessels and improve blood flow, partly by altering nitric oxide and endothelin-1 pathways (pmc.ncbi.nlm.nih.gov). In laboratory studies, magnesium also blocks excess calcium signaling that can damage nerve cells. Because glaucoma involves loss of retinal ganglion cells (the nerve cells of the optic nerve), improving blood supply and preventing cell stress might help. For example, in stroke or heart studies, magnesium sometimes improves blood flow and cell survival. Some researchers have found lower magnesium levels in glaucoma patients. One conference report (in eye fluid and tissues) showed much lower Mg in eyes with glaucoma versus controls (escrs.org). However, those findings need formal publication. In any case, these ideas led to clinical studies testing magnesium in people with glaucoma.
What the Clinical Studies Found
Only a handful of small clinical studies have tested magnesium in glaucoma. We found three main human reports that gave magnesium supplements to glaucoma patients, plus some observational data about magnesium and glaucoma risk.
Gaspar et al (1995) – NTG and Peripheral Blood Flow
In 1995, Gaspar and colleagues reported on 10 patients with glaucoma (likely NTG, though the report lists "glaucoma" broadly) (pmc.ncbi.nlm.nih.gov). They gave 243 mg of oral magnesium per day (121.5 mg tablets twice a day) for one month. They used video nailfold capillaroscopy to examine tiny blood vessels in the fingers, as a sign of peripheral circulation. They also tested visual fields. After one month on magnesium, both visual field measures and peripheral blood flow improved (pmc.ncbi.nlm.nih.gov). In other words, patients showed better vision field test scores and more open capillaries in their fingers. This small study did not have a placebo group, and it did not measure eye-related blood flow directly (just finger capillaries). Nevertheless, it suggested short-term benefit of magnesium on blood flow and vision in glaucoma.
Aydin et al (2010) – NTG Randomized Trial
A stronger study was done by Aydin et al. (2010) in Turkey (pmc.ncbi.nlm.nih.gov). This was a randomized controlled trial in 30 patients with normal-tension glaucoma (NTG). Fifteen patients were given 300 mg of oral magnesium daily for one month, along with their regular glaucoma eye drops. The other 15 patients (control group) continued their regular drops but did not receive magnesium. Before and after one month, the researchers measured visual field indices (mean deviation and pattern standard deviation) and used color Doppler imaging (an ultrasound technique) to measure blood flow velocities in the eye’s arteries.
After one month, the magnesium group’s visual fields improved significantly, compared to the control group (pmc.ncbi.nlm.nih.gov). Mean deviation (a global field score) and pattern SD (field irregularities) both got better in the magnesium group, while they stayed about the same in controls. However, there were no significant changes in ocular blood flow by Doppler in either group, and IOP remained low and unchanged (since these patients were NTG). In summary, Aydin et al found a small but significant visual field benefit from 300 mg magnesium for one month, despite no detectable increase in measured eye blood flow (pmc.ncbi.nlm.nih.gov).
This study was stronger (randomized, controlled) but still small (15 per arm) and short (1 month). It was not reported as double-blind, so placebo effects cannot be ruled out. Nonetheless, it provided evidence that oral magnesium might help NTG patients’ visual field in the short term (pmc.ncbi.nlm.nih.gov).
Akioud et al (2022) – POAG “GlaucoMag” Study
More recently, a single-center study from Morocco (the “GlaucoMag” study) looked at magnesium in primary open-angle glaucoma (www.researchgate.net) (www.researchgate.net). This was non-randomized (no placebo group). It included 46 patients with POAG who all had IOP ≤ 19 mmHg and good vision (to minimize vision changes from lens problems). Each patient took one 300 mg magnesium tablet daily, for 6 months. Eye exams (including Goldmann tonometry for IOP, perimetry for visual field, and OCT scans for RNFL and GCC thickness) were done at baseline, 3 months, and 6 months (www.researchgate.net).
After 3 and 6 months of magnesium, the average visual field scores improved (mean deviation scores “regressed” toward normal, meaning less vision loss) (www.researchgate.net). On OCT scans, nerve fiber layer (RNFL) and ganglion cell layer (GCC) thickness were stable, i.e. not thinner than at baseline. Mean eye pressure also fell significantly in this group over 3-6 months (www.researchgate.net) (from a mean IOP of 16 mmHg downward). In fact, 71.9% of patients had improved visual fields on magnesium (vs 33% of a historical control group), and the magnesium-treated group ended with significantly lower IOP than untreated controls (escrs.org) (escrs.org) (an observation from this or related work). The authors concluded that daily magnesium helped slow glaucoma progression and improve vision, in these patients (www.researchgate.net).
However, this study has major limitations. It was not randomized or blinded, and it lacked a proper control group. All patients knew they were taking supplements, and there could be placebo effects. Also, since all patients were on glaucoma drops already, any improvement might partly reflect better adherence or natural variation. The positive results could be influenced by many biases. Still, as an uncontrolled report, it suggests that 300 mg/day magnesium for months did not harm patients and might be associated with better field results and slightly lower IOP (www.researchgate.net).
Effects on Vision, Blood Flow, and Nerve Thickness
Across these studies, magnesium appeared to help visual field outcomes in glaucoma. Both Gaspar et al (1995) and Aydin et al (2010) saw short-term improvements in visual field scores with one month of oral magnesium (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The Moroccan POAG study also reported better mean deviation scores after a few months of magnesium (www.researchgate.net). This is encouraging, but such field changes can fluctuate easily. In the Aydin trial, the field improvements were statistically significant though modest. In the uncontrolled GlaucoMag study, most patients improved on magnesium, but without a placebo group it is hard to be sure how much of that was real drug effect versus normal measurement variability or learning on the test.
The blood flow effects were mixed. Gaspar et al saw improved peripheral capillary blood flow in nails (pmc.ncbi.nlm.nih.gov), suggesting vessels dilated. Aydin et al, however, measured blood flow in the eye’s arteries by color Doppler ultrasound and found no change after magnesium (pmc.ncbi.nlm.nih.gov). Thus, objective evidence that magnesium raises eye perfusion is still lacking. None of the studies measured something like ocular perfusion pressure directly, except Gaspar’s indirect nailfold test.
On IOP, only the Moroccan study noted a drop when patients took magnesium (www.researchgate.net). It reported a “significant” IOP reduction over 3–6 months of supplementation. But this was uncontrolled, so it is unclear if magnesium truly lowered eye pressure, or if patients coincidentally improved control of their glaucoma drops. Both Gaspar and Aydin did not report any change in IOP (Aydin’s patients already had normal pressures by definition). In short, there is no strong evidence that oral magnesium directly lowers IOP.
The OCT nerve scans (RNFL/GCC thickness) were only reported in the 2022 POAG study. There, nerve layers were stable over 6 months of magnesium (www.researchgate.net). This suggests no unexpected thinning occurred, but without a comparison group we cannot tell if magnesium prevented loss or if RNFL would have been stable anyway. No OCT changes were reported in the other trials.
Dietary Magnesium and Glaucoma Risk
Besides intervention trials, one large observational study in the U.S. looked at dietary magnesium intake and glaucoma risk (from NHANES survey data, 2005–2008) (pmc.ncbi.nlm.nih.gov). In that analysis of 6,180 adults, meeting the recommended magnesium intake (roughly 300–400 mg/day) was not associated with lower glaucoma risk overall. The odds ratio was about 1.0 (no difference) for glaucoma in those getting enough magnesium versus less (pmc.ncbi.nlm.nih.gov). In other words, people who ate the recommended magnesium did not have significantly different rates of glaucoma than those with lower intake. Some subgroup analyses hinted at possible benefits in specific groups (like younger patients or those with high blood pressure), but these were inconsistent. Overall, this suggests no clear protective effect of normal dietary magnesium at a population level (pmc.ncbi.nlm.nih.gov). However, dietary surveys have limits: they rely on self-reported food intake and include undiagnosed glaucoma, so the evidence is weak.
Quality of the Evidence and Study Differences
The existing studies have many limitations. All clinical trials so far have been small, typically under 50 patients, and usually just a month or a few months long. Only one (Aydin 2010) was randomized, and none were double-blind or placebo-controlled. Some improvements (especially in visual fields) could reflect placebo effect or test learning. Trial designs varied widely: for NTG versus POAG, for dosing (243–300 mg/day), and for follow-up time (1 month vs 6 months). Outcome measures also differed. Earlier studies did not use modern imaging (only the 2022 study used OCT), and only one used objective blood flow imaging. Because of these differences, the results are heterogeneous and hard to compare directly.
Experts note that “only two clinical studies support the beneficial role of magnesium in glaucoma,” indicating how sparse the evidence is (pmc.ncbi.nlm.nih.gov). The risk of bias is high: Gaspar’s study lacked controls, and the recent POAG study gave magnesium to everyone. The randomized NTG trial was better, but with only 30 patients its statistical power is limited. No trial clearly ruled out confounders such as changes in other treatments. Additionally, none of the studies reported side effects in detail; magnesium is generally safe, but high doses can cause diarrhea or interact with some medications. (The doses used were moderate though, and no safety issues were noted in the reports.)
Because of these issues, the quality of evidence is low to moderate. Different patient groups (NTG vs POAG) might respond differently, and the one uncontrolled POAG study suggests a potential QOL benefit that needs confirmation. In summary, the current trials hint at a possible benefit of magnesium on visual fields, but these findings need stronger proof. No study has demonstrated a clear change in objective measures like OCT thickness or long-term vision loss rate.
Gaps and Future Research
Given the uncertainties, there are clear gaps in knowledge. Most importantly, we need well-designed trials. A future study should be randomized, double-blind, placebo-controlled, and large enough to draw reliable conclusions. It should enroll either NTG or POAG patients (or both, in stratified groups) and treat them for at least several months, if not longer. Key outcomes should include visual field tests over time, repeat OCT scans for nerve layer thinning, and IOP monitoring. Good trials would also measure any changes in ocular blood flow using objective methods and record any side effects.
Other gaps include the optimal dosage and form of magnesium. The studies used about 300 mg/day, but it’s unclear if more or less, or a different magnesium salt (oxide vs citrate vs lactate), would be best. It would also help to know if only patients with low magnesium levels benefit. No study measured patients’ blood magnesium before treatment, so we don’t know if deficiency status matters.
Finally, since glaucoma progresses slowly, long-term outcomes (over years) are needed. Future trials might also examine whether magnesium helps in combination with other treatments (like IOP-lowering eye drops) better than drops alone. Ultimately, larger and longer trials will tell us if magnesium supplementation should be recommended or not.
Conclusion
In summary, a few small clinical reports suggest that oral magnesium might modestly improve visual field results in some glaucoma patients (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov) (www.researchgate.net). However, the evidence is far from conclusive. There have been no large, definitive trials. The current data come from limited studies with risk of bias. Magnesium appears safe, but whether it truly slows glaucoma damage is still unproven. Patients should not rely on supplements alone but continue standard glaucoma care. Researchers note that more rigorous human studies are needed before magnesium can be recommended for routine glaucoma treatment (pmc.ncbi.nlm.nih.gov).