There is now evidence that magnesium is deficient in patients with glaucoma. In one Russian study, magnesium levels were found to be several fold lower. In normal subjects, levels were found to be about 180 mg/L whereas in glaucoma patients levels were around 18 mg/L. The role of magnesium supplementation is yet to be evaluated in detail; there is some concern about the toxicity of magnesium in patients with renal complaints. Magnesium deficiency may play a role in glaucoma by impairing mitochondrial function and activating NMDA receptors. One epidemiological study based on a dietary survey however has linked a higher intake of magnesium with an increased risk of glaucoma, so the data is quite hard to interpret really. http://www.ncbi.nlm.nih.gov/pubmed/22461101

Magnesium is found naturally in green vegetables including spinach, nuts and whole grains. It helps the release of energy from food, and is important in the development of healthy bones, nerves and muscles. A typical adult male requires about 400mg of magnesium a day, and an adult female around 300mg daily.

Severe magnesium deficiencies are infact rare. They are more likely in those who have Crohn's disease and kidney disease, also in those who abuse alcohol.