About 45 million Americans wear contact lenses, a safe and effective way to correct vision problems if used properly. But many users either forget or neglect to practice proper care of their lenses.

In the spirit of Save Your Vision Month in March, here are some cautionary tales from the Annals of Emergency Medicine about contact lens wearers, all of whom made the same mistake: sleeping with their lenses still in.

One man who went to a hospital complaining of reduced vision and eye pain said he had worn the same soft contact lenses for two weeks. He did not disinfect his lenses, he slept with them in, and he did not replace them regularly. He needed a corneal transplant to save his right eye.

A teenage girl who bought her contact lenses without a prescription at a chain store slept with them in regularly and developed a corneal ulcer. An 18-year-old man who reported pain, light sensitivity and tearing in his left eye said for more than a year he had been sleeping without removing decorative soft contact lenses he bought at a local store without a prescription. After 10 days of intense treatment, his vision improved but he was left with a scar.

While some contact lenses are approved by the FDA for overnight wear, they are classified among medical devices with a greater risk for harm because of infection. In 2010, an estimated 1 million outpatient and emergency department visits were reported in the U.S. for corneal inflammation of all types.

Experts say annual visits to renew a prescription is a good time for eye care specialists to reinforce safe care for contact lens use. It’s infinitely better than being reminded of the dangers while being treated in an emergency room.