* Vitamin A and other carotenoids. In countries where malnutrition is widespread, vitamin-A deficiency is linked to blindness. The vitamin is essential for a healthy retina and for strengthening the mucous membranes that surround the eyes. Beta-carotene, a carotenoid that goes to make vitamin A, is also a powerful antioxidant. A Romanian animal study suggests that two other carotenoids, lutein and zeaxanthin, are also important for treating glaucoma, and can reduce damage to retinal nerve cells and the optic nerve (Oftalmologia, 2003; 59: 70-5). Suggested daily dose: 25,000 IU

* Vitamin C. In one study, high doses of this powerful antioxidant vitamin, given intravenously, dramatically improved patients with open-angle glaucoma (Eye Ear Nose Throat Monthly, 1967; 46: 1502-8). Those with initially high eye pressures showed the biggest improvements, and the effects lasted for up to eight hours. Suggested daily dose: 3000 mg

* Vitamin E. This and other fat-soluble antioxidants are believed to prevent the eye’s drainage system from deteriorating as well as inhibiting cell death (Br J Nutr, 2004; 91: 809-29). Suggested daily dose: 500 mg

* B vitamins. Glaucoma patients are often highly deficient in vitamin B1 (thiamine) (Ann Ophthalmol, 1979; 11: 1095-100). In one study, although vitamin B12 (cobalamin) didn’t lower eye pressure, it did halt visual-field loss for up to five years (Glaucoma, 1992; 14: 167-70). Suggested daily dose: 50 mg (vitamins B1, B2 or B6); 50 mcg (vitamin B12)

* Alpha-lipoic acid (ALA). Supplementing with ALA increased glutathione (antioxidant containing the amino-acid cysteine, needed for cell energy and proper immune function) in red blood cells of glaucoma patients (Vestn Oftalmol, 1992; 108: 13-5). In one Russian study of 45 patients with early-stage glaucoma, one group was given 150 mg/day of ALA for a month, another was given 75 mg/day for two months and a third group used only medicated eyedrops. The most improvement in eyesight and in fluid release was seen in the patients taking the highest dose of ALA, despite the shorter treatment time (Vestn Oftalmol, 1995; 111: 6-8).

* Magnesium, zinc and iron. Deficiencies in these minerals are associated with glaucoma (Vestn Oftalmol, 1994; 110: 24-6). In one study, 121.5 mg of magnesium improved the eyesight of glaucoma patients (Ophthalmologica, 1995; 209: 11-3).

A number of herbal and plant extracts may also benefit glaucoma patients. These include:

* Ginkgo biloba. This herb can successfully treat glaucoma and even improve damage to the visual field (Ophthalmology, 2003; 110: 359-62). It works by enhancing the general blood circulation (J Ocul Pharmacol Ther, 1999; 15: 233-40), reducing glaucoma-inducing vasospasm (where blood flow is decreased by a sudden contraction of blood vessel walls) and thinning the blood. Ginkgo also reduces cell toxicity and cell death (Med Hypoth, 2000; 54: 221-35).

* Coleus forskohlii. Forskolin, the active ingredient in this plant, is involved in the production of cyclic adenosine monophosphate (cAMP), which decreases eye fluid flow, thereby decreasing eye pressure. A number of studies have shown that eyedrops containing forskolin can significantly lower eye pressure for at least five hours. Indeed, in one, it decreased the aqueous flow rate by 34 per cent in healthy human volunteers (Lancet, 1983; i: 958-60; Exp Eye Res, 1984; 39: 745-9).

* Salvia miltiorrhiza (dan shen). Often used in traditional Chinese medicine, this plant’s beneficial effects on the microcirculation of retinal nerve cells and the optic nerve have been demonstrated in animals with ocular hypertension (Chin Med J [Engl], 1993; 106: 922-7; Zhonghua Yan Ke Za Zhi, 1991; 27: 174-8). Nevertheless, it is important to remember that findings from animal studies do not necessarily apply to humans.