Contact lenses offer a convenient way to correct vision. They are designed for specific wear schedules, classified as either daily wear or extended wear, with extended wear approved for limited overnight use under professional guidance. When lenses are worn longer than recommended, or especially when sleeping in daily-wear lenses, this disrupts the delicate balance of the eye’s natural environment. Ignoring the prescribed wear time places the ocular surface under stress, which can range from minor irritation to serious, sight-threatening conditions.
Oxygen Deprivation and Corneal Swelling
The primary physiological issue resulting from overwearing contact lenses is a lack of oxygen reaching the cornea. Unlike most body tissues, the cornea contains no blood vessels and must draw its necessary oxygen directly from the air and the tear film. A contact lens acts as a physical barrier, significantly reducing this oxygen supply, a condition known as hypoxia.
When the cornea is starved of sufficient oxygen, it cannot function properly and begins to swell, a response called corneal edema. This swelling occurs because the lack of oxygen impairs the function of corneal cells responsible for pumping excess fluid out of the tissue. The resulting fluid buildup can cause the cornea to thicken, sometimes exceeding the 15% threshold considered pathological.
Corneal edema can initially manifest as hazy or blurry vision, often noticed upon waking up after sleeping in lenses. Chronic or severe hypoxia can also trigger the development of tiny, fluid-filled pockets called microcysts beneath the corneal surface. This ongoing oxygen deficiency compromises the cornea’s defenses, making it more vulnerable to subsequent complications.
Acute Discomfort and Irritation
The immediate, non-infectious symptoms experienced after exceeding the recommended wear time include ocular redness, or hyperemia. This occurs when the blood vessels in the conjunctiva become visibly dilated, a reaction to the irritation and lack of oxygen caused by the overworn lens.
The lens material itself can contribute to irritation, especially as it dries out and accumulates deposits from the tear film over time. This leads to a foreign body sensation, making the eye feel scratchy or gritty. Excessive dryness can cause temporary vision changes, as the irregular surface of the lens disrupts the light entering the pupil.
The eye may also respond with excessive tearing, or lacrimation, as a protective reflex against discomfort and dryness. While these acute symptoms are temporary and resolve shortly after lens removal, they serve as a clear warning of undue stress. Persistent or severe discomfort indicates a need for professional evaluation before resuming lens wear.
Serious Risks of Infection and Damage
Overwearing contact lenses significantly increases the risk of severe, vision-threatening complications, particularly microbial keratitis. Overnight wear, even occasionally, carries a risk of corneal infection that is five times higher than daily wear. The prolonged presence of a lens traps bacteria and other microorganisms against the corneal surface, preventing the natural flushing action of blinking and tears.
This increased microbial load, combined with the compromised corneal surface due to hypoxia and micro-abrasions, creates an environment ripe for infection. The most feared outcome is a corneal ulcer, an open sore caused by the infectious process, often involving bacteria like Pseudomonas aeruginosa. A corneal ulcer can rapidly progress, causing intense pain, light sensitivity, and a pus-like discharge.
Even with aggressive treatment, an ulcer can leave permanent, opaque scarring on the cornea, which interferes with vision and may require a corneal transplant. A long-term structural change resulting from chronic oxygen deprivation is corneal neovascularization, where new, abnormal blood vessels grow into the normally clear cornea. These vessels are the body’s attempt to supply oxygen to the starved tissue, but their presence can cause inflammation and further compromise vision.
Steps to Take Immediately After Overwearing
If you realize you have overworn your contact lenses, especially if you have slept in them, remove the lenses as soon as possible. If the lenses feel stuck or the eye is extremely dry, resist the urge to pull them off forcibly, which can cause painful abrasions. Instead, liberally apply rewetting or lubricating eye drops to restore moisture and allow the lens to move freely before gently removing it.
After removal, give your eyes a rest and avoid wearing contact lenses for at least 24 hours, switching to glasses instead. This period allows the corneal tissue time to recover from the lack of oxygen and stress. While mild redness and irritation may resolve on their own, monitor your eyes closely for any symptoms that signal a more serious problem.
You must seek immediate consultation with an eye care professional if you experience severe eye pain, a sudden decrease in vision, extreme sensitivity to light, or a persistent discharge. These symptoms are red flags for a developing corneal infection or ulcer, which requires prompt medical attention and often prescription-strength antibiotic drops. Do not attempt to self-treat severe symptoms, as delaying care can result in permanent vision loss.