Contact lenses are carefully regulated medical devices designed for temporary vision correction. Continuously wearing them, especially beyond the prescribed schedule, introduces severe and escalating risks to ocular health. The primary danger stems from obstructing the cornea’s natural ability to receive oxygen. Failing to remove these devices prevents the cornea from accessing the necessary oxygen and moisture for normal cellular function, immediately setting the stage for physiological damage and later, life-altering complications.
The Immediate Physiological Damage
The cornea lacks blood vessels and draws the vast majority of its oxygen directly from the air. A contact lens acts as a physical barrier that restricts this oxygen flow, a condition known as corneal hypoxia. When oxygen supply is significantly reduced, the corneal cells switch to anaerobic respiration, resulting in the accumulation of lactic acid. This metabolic waste draws water into the cornea, causing it to swell in a condition called corneal edema.
Edema initially manifests as hazy or blurred vision, often noticeable after long periods of wear. Swelling compromises the structural integrity of the cornea and impairs the function of the epithelial cells. When this protective barrier is weakened, the eye becomes highly susceptible to infiltration by infectious agents.
The Risk of Severe Eye Infections
The most urgent and sight-threatening consequence of contact lens overwear is the increased likelihood of developing microbial keratitis, commonly known as a corneal ulcer. Overwearing lenses causes microscopic abrasions and compromises the corneal epithelium, allowing bacteria, fungi, or protozoa to invade the underlying tissue. The warm, moist environment trapped beneath a compromised lens creates an ideal breeding ground for these pathogens.
One particularly aggressive bacterial culprit is Pseudomonas aeruginosa, which can cause acute necrotizing keratitis. This infection can progress quickly, sometimes leading to significant tissue destruction and irreversible scarring in as little as 24 hours. Equally concerning is Acanthamoeba keratitis, a devastating infection caused by a free-living amoeba often found in tap water and soil. Sleeping in lenses or exposing them to water significantly raises the risk of this infection, which is notoriously difficult to treat. Both Pseudomonas and Acanthamoeba infections carry a high risk of permanent vision loss, often requiring surgical intervention like a corneal transplant.
Permanent Changes to Eye Health
Beyond the immediate threat of infection, chronic oxygen deprivation and mechanical irritation from continuous lens wear can lead to long-term structural changes in the eye. One such chronic condition is corneal neovascularization, the abnormal growth of new blood vessels from the limbus into the clear corneal tissue. This is the eye’s attempt to compensate for the lack of oxygen by delivering blood-borne oxygen to the hypoxic cornea.
These newly formed vessels can obstruct vision if they grow into the central visual axis, and their presence indicates long-term physiological stress. Another chronic issue is Giant Papillary Conjunctivitis (GPC), an inflammatory reaction that affects the inner surface of the upper eyelid. GPC is characterized by the formation of enlarged, dome-shaped bumps on the conjunctiva, which is often triggered by an inflammatory response to protein and lipid deposits on the lens surface. This condition often leads to lens intolerance, making it impossible to comfortably wear contacts in the future due to excessive itching, mucus discharge, and lens movement.
Recognizing Warning Signs and Seeking Help
Recognizing the early indicators of a complication is paramount, as a corneal infection can become a medical emergency in a matter of hours. The most telling signs that necessitate immediate action include sudden, sharp eye pain or a persistent foreign body sensation that does not resolve after lens removal. A significant increase in eye redness, particularly if it is localized or severe, is a major warning sign that should not be ignored.
Other symptoms demanding immediate attention include a notable reduction in visual clarity, excessive light sensitivity (photophobia), and any discharge, such as a thick or watery secretion. If any of these signs appear, the contact lenses must be removed immediately and an eye care professional (ECP) must be contacted without delay. Delaying consultation, even by a few hours, can dramatically worsen the prognosis for vision recovery, as these symptoms can indicate a rapidly progressing, sight-threatening infection.