While some contact lenses are designed to be worn at night, most are not. Sleeping in contacts that are meant for daily wear can lead to infections, corneal ulcers, and other health problems that can cause permanent vision loss.
Contact lenses reduce the much-needed supply of oxygen to the cornea, or the surface of your eye. Normally, the cornea gets oxygen both from blood vessels in the eyelid at night and from the air during the day. A regular contact lens user relies on the nighttime supply to keep the eye healthy, so cutting off nighttime oxygen can be devastating.
During the day, pollutants from the air get into your eyes, and some work their way under your lenses. The combination of protection of the closed eyelid, reduced movement of the eye and eyelid, and low oxygen create ideal conditions for bacterial and viral infections to grow, according to an article in Optometry and Vision Science.
Conjunctivitis (Pink Eye)
Conjunctivitis is one of the most common, though least dangerous, consequences of sleeping in contacts, according to the American Optometric Association. Pink eye is an inflammation of the conjunctiva, which covers the white of the eye and lines the inside of the eyelid. It is usually caused by a viral infection. In addition to the cosmetic drawbacks of having oozing and discolored eyes, pink eye is often itchy and uncomfortable.
Giant papillary conjunctivitis (GPC) is a special form of this disease in which bumps develop on the inner surface of the eyelid. Contact lens wearers are most affected by this disease. GPC is painful and makes your eyes sensitive to light. The first step to treatment is taking your lenses out, which actually increases the pain initially.
Keratitis is inflammation similar to conjunctivitis. It affects the cornea—the clear part of the front of your eye that you see through. In addition to common symptoms of conjunctivitis, keratitis also damages your vision. The Center for Contact Lens Research (CCLR) states that sleeping in contacts is associated with a 10 times greater risk of microbial keratitis.
Keratitis can be caused by infections of amoebae, bacteria, and fungi. Amoebic keratitis is the most serious and causes vision loss. Contact Lens Acute Red Eye (CLARE) is keratitis often comes on suddenly during sleep, causing intense pain and sensitivity to light.
Keratitis can cause corneal ulcers, which lead to potentially permanent blindness if not treated properly.
Even if you avoid infection, deprivation of oxygen from nighttime contact lens wearing causes the eye to grow more blood vessels to increase the supply of blood to the cornea. Neovascularization impairs vision because vessels inhibit light from traveling through the cornea normally.
Sleeping in contacts is not worth it, no matter how tempting it may seem. Good contact lens care is crucial to maintaining the health of your eyes.