Table 1.

Overview of investigated vitamins retrieved from the systematic review.

Vitamin	Vitamer Chemical Name	Remarks	Relevance to the Eye	Main Sources	Rich Food Sources
A	Retinol (A1)	Preformed retinols (or active form)—is immediately available to the body	Important for rhodopsin found in the retina for visual phototransduction, and protects against free radicals i.e., acts as an antioxidant	Animal products	Liver, eggs, cheese, butter, dark green vegetables (spinach) and carrots
		Precursors (or provitamins)—has to be metabolized into an active form	Important for rhodopsin found in the retina for visual phototransduction, and protects against free radicals i.e., acts as an antioxidant	Plant products	Vegetables and fruits with orange pigments (known as carotenoids)
B-complex	Thiamin (B1)	Some flavonoids may antagonize vitamin B1	Serve as coenzymes in catabolism of amino acids, carboxylase, cell division and growth, and DNA synthesis and repair in every cell of the body	Animal/plant products	Yeast extract, cereal grains (especially in the outer layer of the grain and in the germ), meat (pork), nuts, peas, and beans
	Riboflavin (B2)	Primary coenzyme form of vitamin B6	Used in the treatment of corneal ectasia for strengthening of corneal collagen tissue. It can also be used as a prophylaxis for migraine: a potential risk factor for glaucoma	Animal/plant products	Milk, cheese, eggs, green leafy vegetables, almonds, and mushrooms
	Niacin (B3)	May be converted to nicotinamide, which is another form of vitamin B3	Involved in vasodilatation of among others retinal arterioles. It improves endothelial dysfunction	Animal/plant products	Fish, dates, nuts, and cereal grains
	Pyridoxin (B6)	Dietary vitamin B6 cannot be used without vitamin B2 (Riboflavin)	Involved in neurotransmitter synthesis. Plays a role in the treatment of gyrate atrophy of the choroid and retina	Animal/plant products	Meat (pork), bananas, chickpeas, potatoes, and pistachios
	Folate (B9)	Synthetic form, used in supplements and food processing, is called Folic acid	When combined with vitamin B12 it reduces homocysteine levels, which induces vascular injury, alterations in extracellular matrix remodeling, and neuronal cell death	Plant products	Cereal grains (especially in the outer layer of the grain and in the germ), dark green leafy vegetables, nuts, peas, and beans
	Cobalamin (B12)	Should be in balance with folic acid and iron	Coenzyme involved in the metabolism of every cell of the body. Deficiency can results in elevated homocysteine levels, optic neuropathy, and irreversible damage to nervous system	Animal products	Fish, red meat, eggs, and cheese
C	Ascorbic acid	Oxidized form of vitamin C is reduced by glutathione, which helps maintain vitamin C in a reduced (active) form	Enzymatic cofactor for collagen synthesis and very effective in scavenging of reactive oxygen species, i.e., vitamin C is an important non-enzymatic antioxidant	Plant products	Peppers, green leafy vegetables, and in many fruits (kiwis, strawberries, oranges, guavas, and papaya)
D	Cholecalciferol	Most important subtype in humans is vitamin D3. In the liver vitamin D is converted to 25-hydroxyvitamin D, which is used as a biomarker	Responsible for intestinal absorption of several minerals including calcium, iron, magnesium, and zinc	Sunlight exposure	Mushrooms, cod liver oil, fish, and cereals
E	Tocopherol	Excessive vitamin E may lead to vitamin K * deficiency resulting in bleedings	Plays a role in the oxidation of low-density lipoproteins (LDL) and prevents the production of damaging free radicals. Therefore vitamin E is seen as an important antioxidant. Deficiency might result in peripheral neuropathy and retinopathy	Plant products	Nuts (especially almonds), sunflower oil and seeds, avocados, and dark green leafy vegetables

* = None of the retrieved studies assessed the relation between vitamin K and glaucoma.