While contact lenses are safely used by millions of people every day, they do carry a risk of eye infection. Factors contributing to infection can include:
Use of extended-wear lenses;
Reduced tear exchange under the lens;
Environmental factors;
Poor hygiene.
The single best way to avoid eye infections is to follow proper lens care guidelines as prescribed by your eye care professional. In particular, including a "rub and rinse" step in the lens cleaning process, minimizing contact with water while wearing contact lenses and replacing the lens case frequently can help reduce the risk of infection.