Wearing contact lenses longer than the recommended duration, or sleeping in lenses not approved for overnight use, poses substantial risks to eye health. Contact lenses are medical devices designed for specific wear schedules, and disregarding these limits can lead to consequences ranging from mild discomfort to severe, sight-threatening infections. Understanding the underlying physiological stress caused by this misuse is important for protecting the delicate structures of the eye.
The Mechanism of Oxygen Deprivation
The cornea, the transparent front dome of the eye, lacks blood vessels, relying instead on oxygen absorbed directly from the surrounding air and dissolved in the tear film. When a contact lens is placed on the eye, it acts as a physical barrier, naturally reducing the amount of oxygen that can reach the corneal surface. Modern lenses are made from materials like silicone hydrogel to allow for high oxygen transmission, but prolonged wear still restricts this supply, especially when the eye is closed during sleep.
This reduced oxygen supply creates a condition known as corneal hypoxia, which forces the corneal cells to switch to less efficient anaerobic respiration. A common physiological response to this stress is corneal edema, or swelling, as the cellular pumps responsible for maintaining the cornea’s dehydrated state begin to fail.
Acute Symptoms of Overwearing
Exceeding the recommended wear time often triggers physical discomforts. The most common sign is redness, medically termed conjunctival injection, which is a visible dilation of blood vessels on the white of the eye. This often accompanies a sensation of dryness or a gritty feeling, as the lens material absorbs moisture and the tear film becomes unstable.
The corneal swelling caused by oxygen deprivation can lead to a noticeable blurring of vision. Users may also experience mild pain or a foreign body sensation, as the compromised corneal surface becomes more sensitive. These symptoms signal that the cornea is under stress and requires an immediate break from the lens.
Severe Risk of Eye Infection
The most serious consequences of overwearing contact lenses stem from the combination of mechanical irritation and a weakened, oxygen-starved cornea. When the cornea is deprived of oxygen, the superficial layer of cells, the epithelium, becomes vulnerable and prone to microscopic abrasions. These breaks in the protective barrier create an entry point for bacteria and other microbes that naturally colonize the lens surface and the tear film.
This environment is a breeding ground for severe infections, collectively known as microbial keratitis, a sight-threatening condition. Overnight wear is a significant risk factor, as the closed eyelid dramatically lowers oxygen levels, and the stagnant environment under the lens promotes bacterial growth. Untreated microbial keratitis can rapidly progress to a corneal ulcer, which is an open sore on the cornea. If the infection is not treated promptly, the resulting inflammation and scarring can cause permanent vision loss.
Immediate Action Steps
If you realize you have overworn your contact lenses and are experiencing discomfort, the first step is to remove the lenses immediately. If the lenses feel stuck or the eye is very dry, do not force the removal; instead, use preservative-free rewetting or lubricating drops to hydrate the eye and allow the lens to loosen safely. Once removed, switch to wearing glasses to give the cornea time to recover and repair any surface damage.
It is important to differentiate between mild irritation and a medical emergency. You must seek immediate professional attention from an eye care provider if you experience:
- Persistent pain
- Increased sensitivity to light
- A noticeable discharge
- Any sudden change in vision
These are signs that a serious infection or corneal ulcer may be developing, which requires immediate diagnosis and treatment with prescription medication. Do not resume contact lens wear until an eye doctor has examined your eyes and confirmed that the tissue is fully healed.