While people normally think of vitamins and supplements as helpful, a large number of supplements can cause rather than cure eye problems. Some supplements cause problems only when taken in large quantities, while others can cause problems at any dose. Applying certain supplements topically rather than taking them orally can also cause problems in some cases. Check with your practitioner before taking any supplements. Any time you experience a change in vision, tell your medical practitioner about any supplements you may be taking.
Vitamin A
Vitamin A is a fat soluble vitamin, which means excess amounts can be stored in your body. Vitamin A overdose can be acute, resulting from taking too much at one time, or chronic, meaning that it builds up in your body. At normal doses, vitamin A helps vision, particularly night vision. Chronic vitamin A overdose normally occurs when you take more than 25,000 international units, or IU, per day, according to MedlinePlus, while acute poisoning occurs with doses of several hundred thousand IU. Eye problems that occur with an overdose of vitamin A include blurred vision, double vision in young children and other vision changes.
Echinacea
Echinacea, commonly used to treat colds, can cause conjunctivitis, inflammation of the conjunctiva, the thin layer of tissue that covers the lower inner eyelid and part of the eyeball, reports ophthalmologist Cary Silverman on his website EyeCare 2010.
Gingko Biloba
Gingko biloba, often taken to improve memory and brain function, also acts as a blood thinner. People who already take blood thinners or who have blood-clotting disorders may develop bleeding in the blood vessels of the retina, the portion of the eye that contains the cells necessary for vision, Silverman warns.
Licorice
Licorice supplements, which differ from licorice candy, are used in alternative medicine to treat upper respiratory infections and stomach problems. In large quantities, licorice can cause vasospasm, spasms of the blood vessels in the retina, decreasing blood flow to the retina and causing transient vision loss, the IU website states.
Niacin
Niacin is prescribed medically to treat high triglyceride and cholesterol levels. Niacin doses of 3 g or more daily can cause cystoid macular edema, also called CME, swelling in the central part of the retina, the macula, which contains the cells responsible for clear, focused vision, Indiana University School of Optometry website reports. Discontinuing niacin clears up CME.
