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reference
Aydin B, Onol M, Hondur A, et al. The effect of oral magnesium therapy on visual field and ocular blood flow in normotensive glaucoma.Eur J Ophthalmol.2010;20(1):131-135.
design
Controlled clinical trial to evaluate the effect of oral magnesium therapy on ocular blood flow and visual field perimetry indices in patients with normotensive glaucoma (NTG). Measurement of blood magnesium levels, visual field analysis and color Doppler imaging of the orbital vessels were performed before treatment and after one month.
Participant
Fifteen patients with NTG (study group) received 300 mg of oral magnesium citrate for one month, while 15 patients with NTG (control group) received no treatment.
Key findings
In the study group, the visual field measurements improved significantly: the mean deviation improved from -3.7+/-1.9 (mean +/- standard deviation) at the start of the study to -2.5+/-1.8 after one month (P<0.05) and the pattern standard deviation improved from 3.6+/-2.3 at baseline to 2.8+/-2.6 after 1 month (P<0.05). Color Doppler imaging indices did not change after magnesium therapy. Mechanisms other than increased ocular blood flow may be responsible for the improvement in visual field caused by oral magnesium therapy.
Effects on practice
Glaucoma reflects damage to the optic nerve. Glaucoma can cause a gradual loss of peripheral vision, leading to tunnel vision and eventual blindness. Normally, damage to the optic nerve is caused by increased pressure in the eye resulting from greater production of ocular fluid (aqueous humor). Normal intraocular pressure (IOP) is approximately 10 to 21 mm Hg. In chronic glaucoma, intraocular pressure is usually slightly to moderately elevated (22 to 40 mm Hg). In acute glaucoma, intraocular pressure is more than 40 mm Hg.
In some cases, glaucoma develops in people with normal intraocular pressure. This form, called low-tension glaucoma or normotensive glaucoma, accounts for about 25 to 30 percent of all glaucoma cases in the United States.
Low-tension glaucoma, or normotensive glaucoma, accounts for approximately 25 to 30 percent of all glaucoma cases.
Since increased intraocular pressure is not a factor in NTG, other factors are responsible for optic nerve damage. Suggested causes include:
- Reduzierter Blutfluss
- Früher Nervenzelltod
- Nervenreizung
- Übermäßige Glutamatproduktion
- Autoimmunerkrankung
The disease occurs more often in women than men and affects adults with an average age of 60 years. A common risk factor for NGT is low blood pressure.
This study showing benefits in visual field improvement after oral magnesium supplementation is of great importance because NTG cannot be effectively treated with conventional medications. It is also extremely thought provoking as a mechanism of action needs to be identified.
Because the benefits of magnesium therapy are not due to changes in blood flow, it is possible that the benefit is related to the reduction of elevated glutamate concentrations in the extracellular spaces surrounding the optic nerve. Glutamate is an important excitatory neurotransmitter and an important neurotoxin that promotes neuronal cell death. It's definitely connected to NTG. Since magnesium has been shown to stimulate blockade of neuronal receptors, resulting in a reduction in glutamate release during ischemia,1This mechanism could also explain its advantages in NTG.