Contact lenses are most often designed to be worn on a monthly, bi-weekly, or daily schedule. When lenses are worn past the recommended amount of time, the material starts to deteriorate. Protein deposits on the lens will increase, and will cause the lens to become cloudy, and less comfortable. It is important that contact lens wearers follow the recommended wear schedule given to them by their eye doctor. While it may seem harmless, contact lens over-wear can lead to problems later.

Contact lens over-wear is a problem that eye care professionals have been trying to combat for many years. Even with newer materials that allow more oxygen and moisture to the eye, patients continue to be seen for a variety of problems associated with the overuse of both rigid gas permeable and soft hydrogel contact lenses. Approximately twenty to thirty percent of contact lens wearers have reported incidences of contact lens over-wear.

Corneal ulcers are one problem that can arise from wearing contact lenses after they are supposed to be thrown away.  Because the lenses will have started deteriorating, the edges can begin to scrape against the cornea, creating tiny tears which can become infected with bacteria from the lens.

Among the many eye conditions that can occur, corneal ulcers cause the most eye damage. Symptoms of a corneal ulcer include redness of the eye, swollen eyelids, discharge, light sensitivity, and blurred vision. If a corneal ulcer goes untreated, it can cause permanent damage to the cornea, including scarring. Corneal scarring, at a minimum causes a haze in the vision. In some cases, corneal scarring must be treated by a corneal transplant. Even if the ulcer does not cause permanent scarring, it can take several months to heal completely. In extreme cases, corneal perforation can occur. Corneal perforation, while treatable, is painful, and requires treatment from an optometrist or ophthalmologist.