Contact lenses are a convenient, effective, and often life-changing solution for vision correction. Offering clear sight without the need for glasses, they’re favored by millions worldwide for their practicality and aesthetic benefits. However, for many users, questions about safe usage practices remain—especially regarding whether it is safe to sleep in contact lenses. While some contact lenses are marketed as suitable for extended or overnight wear, the consensus among eye care professionals is that sleeping in contact lenses increases the risk of significant eye complications, even when using lenses designed for such use.
The risks associated with sleeping in contact lenses stem from the way lenses interact with the cornea, the clear, dome-shaped surface of the eye. Wearing lenses during sleep reduces oxygen supply to the cornea, creates a hospitable environment for bacteria, and limits natural cleaning processes, which can lead to infections, inflammation, and in severe cases, vision loss. Even for lenses approved for extended wear, the risks remain higher compared to removing them before sleeping. Understanding these risks and the science behind them is crucial for maintaining eye health and avoiding complications.
In this article, we will examine the relationship between contact lenses and eye health, the dangers of wearing lenses while sleeping, and expert recommendations for safe lens use. This deep dive will provide clarity on why removing your contact lenses before bed is one of the simplest yet most effective ways to protect your vision.
The Basics of Contact Lenses and Eye Health
Contact lenses are medical devices placed directly on the cornea to correct refractive errors like nearsightedness (myopia), farsightedness (hyperopia), astigmatism, and presbyopia. They work by refracting light to focus correctly on the retina, ensuring clear vision. Modern lenses are made from advanced materials, including soft silicone hydrogel, which is designed to be comfortable and allow oxygen to pass through to the cornea. Oxygen permeability is critical for corneal health because, unlike most tissues in the body, the cornea lacks blood vessels and relies on oxygen from the air and tears.
There are various types of contact lenses, ranging from daily disposables to extended-wear lenses that can be used continuously for up to 30 days. However, no matter the type, contact lenses reduce the amount of oxygen reaching the cornea. During waking hours, this reduced oxygen supply is mitigated by blinking and tear exchange, which help maintain corneal hydration and health. When you sleep with contact lenses in, these mitigating factors are eliminated, which significantly increases the risk of complications.
What Happens When You Sleep in Contact Lenses?
When you sleep, your eyelids close, naturally reducing the amount of oxygen that reaches your cornea. Sleeping in contact lenses further exacerbates this oxygen deprivation because the lens acts as a physical barrier, limiting oxygen flow even more. This oxygen shortage, or hypoxia, weakens the cornea, impairing its ability to resist infections and heal itself from minor injuries.
Additionally, sleeping in contact lenses disrupts the eye’s natural cleaning processes. Normally, tears help wash away debris, dead cells, and bacteria from the surface of the eye. With your eyes closed and lenses in place, tear exchange is minimal, allowing deposits and pathogens to accumulate on the lens. These conditions create a perfect environment for harmful microorganisms to thrive, increasing the likelihood of infections.
The Risks of Sleeping in Contact Lenses
1. Increased Risk of Eye Infections
Sleeping in contact lenses dramatically increases the risk of developing serious eye infections, such as microbial keratitis. Microbial keratitis is an infection of the cornea caused by bacteria, fungi, or parasites. It can lead to redness, pain, blurry vision, sensitivity to light, and in severe cases, permanent vision loss. Studies have shown that people who sleep in their contact lenses are 6 to 8 times more likely to develop microbial keratitis compared to those who remove their lenses before bed.
One particularly concerning organism is Acanthamoeba, a microscopic parasite found in water. If Acanthamoeba infects the cornea, it can cause Acanthamoeba keratitis, a rare but extremely painful condition that often results in scarring and vision loss. Contact lens wearers who sleep in their lenses and have exposure to water—whether from showering, swimming, or using contaminated lens solutions—are at greater risk of contracting this infection.
2. Corneal Inflammation and Ulcers
The cornea is a highly sensitive and delicate structure. Prolonged lens wear, especially during sleep, can lead to corneal inflammation (keratitis) and the development of corneal ulcers. A corneal ulcer is an open sore on the cornea that can result from infections, hypoxia, or mechanical irritation caused by the lens.
Corneal ulcers are extremely painful and can cause symptoms such as severe redness, tearing, discharge, and blurry vision. Without prompt treatment, they can lead to permanent scarring of the cornea, significantly impairing vision. Even with treatment, recovery from corneal ulcers can take weeks, during which patients often experience significant discomfort.
3. Corneal Swelling and Long-Term Damage
Wearing contact lenses during sleep deprives the cornea of oxygen, leading to corneal swelling, or edema. This condition occurs when the corneal cells are unable to maintain proper fluid balance due to hypoxia. Swelling can cause blurry vision, discomfort, and increased light sensitivity. Over time, repeated episodes of hypoxia and swelling can weaken the cornea, making it more prone to infections and injuries.
Chronic oxygen deprivation may also trigger neovascularization, a condition in which new blood vessels grow into the cornea in an attempt to supply it with oxygen. These blood vessels can permanently alter the cornea’s structure and transparency, leading to reduced visual clarity and an inability to tolerate contact lenses in the future.
Are Extended-Wear Lenses Safer?
Some contact lenses are marketed as safe for overnight or extended wear. These lenses are made from silicone hydrogel, a material that allows more oxygen to pass through compared to traditional hydrogel lenses. While extended-wear lenses are designed to reduce the risks associated with overnight use, they are not entirely risk-free.
Research shows that extended-wear lenses still carry a significantly higher risk of complications compared to daily wear lenses. The increased likelihood of infections, corneal ulcers, and inflammation remains a concern. Many eye care professionals recommend that even users of extended-wear lenses remove them before sleeping whenever possible to minimize risks.
Common Misconceptions About Sleeping in Contact Lenses
One common misconception is that occasional overnight wear is harmless. While not every instance of sleeping in contact lenses results in complications, the risks are cumulative. Each time you sleep in your lenses, the cornea experiences hypoxia, and pathogens have more time to accumulate. Over time, these repeated exposures can lead to serious problems.
Another myth is that comfort equates to safety. Many people believe that if their lenses feel fine, there’s no risk in wearing them overnight. However, complications like microbial keratitis or corneal ulcers can develop without noticeable symptoms until they become severe, emphasizing the importance of precaution even when no discomfort is present.
Expert Recommendations for Safe Contact Lens Use
To reduce the risk of complications, follow these guidelines:
- Always remove your contact lenses before sleeping, unless explicitly advised otherwise by your eye care provider.
- Practice good lens hygiene by cleaning your lenses daily with the appropriate solution and replacing them according to the recommended schedule.
- Never expose your lenses to water, including tap water, swimming pools, or hot tubs, as this increases the risk of Acanthamoeba keratitis.
- Use fresh contact lens solution each time you store your lenses, and avoid “topping off” old solution in your lens case.
- Schedule regular eye exams to ensure that your lenses fit properly and to monitor your eye health.
The Role of Oxygen in Corneal Health
The cornea’s reliance on oxygen makes it uniquely vulnerable to complications when oxygen supply is restricted. Oxygen is essential for maintaining the health of corneal cells, supporting tear production, and preventing infections. Reduced oxygen availability during sleep—exacerbated by wearing contact lenses—compromises these functions, making the cornea more susceptible to damage.
Oxygen deprivation over time can result in long-term complications, including corneal thinning, scarring, and loss of transparency. These conditions not only affect vision but may also render the cornea less tolerant to contact lenses in the future, requiring permanent discontinuation of lens use or even surgical intervention.
Conclusion: Better Safe Than Sorry
While contact lenses are a safe and effective method of vision correction when used properly, sleeping in them—whether occasionally or regularly—significantly increases the risk of serious complications. Reduced oxygen supply, bacterial buildup, and impaired tear exchange create conditions that can lead to infections, inflammation, and lasting corneal damage. Even lenses approved for overnight wear carry elevated risks compared to removing lenses before sleep.
Protecting your eye health requires diligence and adherence to recommended practices. Removing your contact lenses before bed, practicing good lens hygiene, and consulting your eye care provider regularly are simple yet effective ways to ensure safe and comfortable lens use. Your vision is precious, and taking steps to safeguard it is always worth the effort.
