Nearly a million Americans visit the doctor each year for eye infections, which are often related to wearing contact lenses, according to a new report.

In 2010, people made 930,000 doctor's visits plus 58,000 emergency department visits in the United States for microbial keratitis, according to the report, from the Centers for Disease Control and Prevention. Microbial keratitis is an infection of the eye's transparent outer covering caused by bacteria, fungi, amebae or viruses.

The biggest risk factor for microbial keratitis is improperly wearing contact lens for example, wearing the lenses overnight, not keeping contact lens cases clean and not replacing cases frequently, the CDC said.

In more than three-fourths (76.5 percent) of the visits, the person was given a prescription for antibiotics, the report found. The researchers estimated that visits for these eye infections result in $175 million in direct health care costs yearly. [7 Absolutely Horrible Head Infections]

Keratitis can cause eye pain, redness, blurred vision and even blindness in severe cases.

In July, a woman in Taiwan reportedly went blind because she left her contact lenses in for six months, and developed an infection from an amoeba.

"Contact lenses can provide many benefits, but they are not risk-free especially if contact lens wearers take shortcuts and don't take care of their contact lenses and supplies," Dr. Jennifer Cope, a CDC medical epidemiologist, said in a statement.

It's estimated that 38 million Americans wear contact lenses. To prevent eye infections, the CDC recommends the following:

  • Wash hands before touching contact lenses.
  • Remove contact lenses before bed, showering or swimming.
  • Rub and rinse contact lenses with disinfecting solution every time they are removed.
  • Replace old contact-solution with fresh solution every time you store your contact lenses in a case.
  • Clean contact lens cases after each use.
  • Replace contact lens cases at least once every three months.

Keratitis can also be caused by factors not related to infection, such as injury to the cornea or chemical exposure, the researchers said, so some of the 1 million doctor's visits may have been for eye problems not caused by infection. published this week in the CDC's Morbidity and Mortality Weekly Report.

Copyright 2014 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.