Contact lenses offer a convenient way to correct vision. While they provide clear sight, eye care professionals consistently recommend removing them before sleep. This protects eye health and prevents complications from prolonged lens wear, especially when eyes are closed. Understanding the physiological reasons behind this guideline helps lens wearers make informed choices for their ocular well-being.
The Cornea’s Oxygen Needs
The clear, dome-shaped front surface of the eye, known as the cornea, is unique because it lacks blood vessels. Instead, it receives its oxygen supply primarily from the air when the eyes are open. This direct atmospheric exchange is important for its transparency and proper function.
When eyelids are closed during sleep, the cornea receives a reduced amount of oxygen, mainly from the blood vessels in the eyelids and the tear film that bathes the eye. Introducing a contact lens creates an additional barrier, further limiting oxygen flow to the cornea. This condition of reduced oxygen is termed “hypoxia.”
Corneal hypoxia can lead to the cornea swelling, a condition called edema, which may cause hazy vision. Over time, chronic oxygen deprivation can alter the structure of corneal cells and may even compromise the cornea’s ability to maintain proper hydration.
Increased Risk of Infection
Sleeping with contact lenses significantly increases the risk of eye infections, making it 6 to 8 times more likely than daily wear. This heightened vulnerability stems from a combination of factors that create an environment conducive to microbial growth. Reduced oxygen supply to the cornea weakens its natural defenses, making it less effective at fighting off bacteria and other microorganisms.
The presence of a contact lens on the eye during sleep also disrupts the natural tear flow and exchange. Tears play a protective role by flushing away debris and microorganisms, but their reduced circulation under a lens allows bacteria to accumulate on the lens surface, forming a sticky layer known as a biofilm. This biofilm provides a protective matrix for bacteria, making them more resistant to the eye’s natural defenses and even some lens solutions.
Contact lenses can also cause minor abrasions or micro-traumas to the corneal surface, especially if they are dry or ill-fitting. These microscopic breaks in the corneal epithelium provide entry points for bacteria and other pathogens, allowing them to penetrate deeper into the eye and initiate an infection.
Specific Eye Complications
Sleeping with contact lenses can lead to several serious eye complications. One severe issue is microbial keratitis, or a corneal ulcer, an infection of the cornea. These painful open sores can be caused by bacteria (Pseudomonas aeruginosa, Staphylococcus aureus), fungi, or parasites like Acanthamoeba. Untreated, corneal ulcers can cause permanent scarring, significant vision loss, or blindness, sometimes requiring a corneal transplant.
Corneal neovascularization is another complication, involving the abnormal growth of new blood vessels into the clear cornea. This happens as the eye tries to compensate for chronic oxygen deprivation. While often asymptomatic early on, these new vessels can cause blurred vision, increased redness, and light sensitivity.
Giant Papillary Conjunctivitis (GPC) is an allergic reaction forming large bumps on the underside of the eyelid. It can be triggered by lens friction, deposits on the lens, or an allergic response to lens material or solutions. Symptoms include a foreign body sensation, itching, excessive mucus, blurred vision, and lens discomfort.
If You Sleep With Lenses Accidentally
If you accidentally fall asleep with your contact lenses in, it is important to avoid immediate, forceful removal. Your eyes will likely be dry, causing lenses to stick, and pulling them out could cause injury. Instead, allow your eyes to rehydrate by blinking several times to encourage natural tear production.
Applying a few drops of sterile rewetting drops or saline solution to each eye can help loosen the dried lenses. Wait a few minutes for the drops to work and for the lenses to rehydrate. Once the lenses feel comfortable and move freely, gently remove them with clean, dry hands.
After removal, discard daily disposable lenses or thoroughly clean and disinfect reusable lenses as recommended. Give your eyes a break from contact lenses for at least 24 hours, wearing glasses instead, to allow recovery from dryness, irritation, or minor swelling. If you experience persistent redness, pain, blurred vision, discharge, or increased light sensitivity, contact an eye care professional promptly, as these could indicate an infection or other complication.