Accidentally falling asleep while wearing standard soft contact lenses is a common mistake. This oversight significantly increases the risk of serious complications for the eye’s surface. Wearing lenses overnight disrupts the natural balance of the eye, creating an environment where health risks are elevated. Understanding the specific biological consequences of this practice is crucial for protecting vision.
Why Oxygen Deprivation is the Primary Concern
The cornea, the clear, dome-shaped front surface of the eye, lacks blood vessels and must receive oxygen directly from the air to maintain its health. A contact lens acts as a physical barrier, partially restricting this oxygen flow even when the eye is open.
This restriction becomes far more pronounced when the eyelid closes during sleep. The cornea is then forced to rely on limited oxygen supplied by blood vessels within the inner eyelid. This combination leads to oxygen deprivation, known as corneal hypoxia. The lack of oxygen causes the cornea to swell slightly, a condition called edema, which weakens its natural defenses and makes it vulnerable to injury or infection.
Common Immediate Symptoms
Upon waking after sleeping in lenses, the most immediate sensations are typically related to dryness and friction. The contact lens loses moisture overnight, often causing it to adhere tightly to the corneal surface. This adhesion results in a gritty, uncomfortable, or burning sensation, often described as feeling like something is stuck in the eye.
The eye often appears bloodshot or red due to surface irritation and inflammation caused by restricted oxygen and friction. Vision may also be temporarily blurred or hazy from the combination of dryness and slight corneal swelling. These transient symptoms are signs of surface stress, distinct from the deeper, more dangerous damage of a severe infection.
Understanding Severe Corneal Infections
The most serious consequence of sleeping in lenses is a dramatically increased risk of severe eye infection, specifically microbial keratitis. Studies show that wearing lenses overnight increases the risk of this vision-threatening infection by six to eight times. The oxygen-deprived and swollen cornea is a compromised host, and the contact lens creates a warm, moist space where bacteria can rapidly multiply.
This environment is an ideal breeding ground for common, aggressive bacteria, such as Pseudomonas aeruginosa. When these microorganisms penetrate the weakened outer layer of the cornea, they cause a deep infection known as a corneal ulcer. A corneal ulcer is a medical emergency because the infection can cause permanent clouding or scarring of the normally transparent cornea. If treatment is delayed, this can lead to permanent vision loss or require a corneal transplant.
What to Do After Sleeping in Lenses
If you wake up and realize your lenses are still in, resist the urge to immediately pull them out. The lens is likely dehydrated and stuck to the cornea, and forcing removal can cause a painful surface abrasion. Instead, apply sterile saline solution or lubricating eye drops liberally to rehydrate the lens and the corneal surface.
After applying the drops, blink gently several times and wait a few minutes until the lens moves freely. Once removed, switch to wearing glasses for a minimum of 24 hours to allow the cornea time to recover full oxygenation and repair minor surface damage.
Any persistent symptoms, such as severe pain, intense sensitivity to light, blurred vision that does not clear, or unusual discharge, are red flags. These symptoms indicate a serious complication and require an immediate, emergency consultation with an eye care professional.