The biggest risk of using contact lenses in the eye is infection. The most serious of the eye infections is keratitis. This infection can be caused by bacteria and other germs. Studies have shown that most people get infected because they do not follow the advice of an eye doctor. The study, conducted in the United States , found that 45 percent of users did not wash their hands before opening or wearing lenses. Other studies have shown that many people spend one to one and a half times more than the maximum lens usage per month. In addition , many people use short-term (two weeks) usable lenses for two to two and a half times longer. It should not be forgotten that contact lenses are a sensitive 'medical device'. Lenses in special liquids in sterilized small containers can become contaminated when they expire. Professor Roger Buckley, associate director of the Vision and Eye Research Unit at Angila Raskin University in the United Kingdom, says the biggest cause of infection is going to sleep at night after contact lenses. Sleeping after contact lenses can increase the risk of corneal infection by 20 times. The cornea is in oxygen crisis as the eyelids are closed while wearing lenses. Due to this, the eyes become weak in dealing with germs.