Contact lenses offer a popular and convenient method for vision correction, but they require strict adherence to replacement schedules and hygiene practices. Using lenses past their intended lifespan, whether through expiration or overuse, poses significant risks. This practice threatens the delicate tissues of the eye and can lead to permanent vision damage.
Defining “Old” Contact Lenses
A contact lens becomes “old” and dangerous in one of two distinct ways: expiration or overwearing. Expired lenses are those that have remained sealed in their original packaging past the date printed on the box. The primary concern is that the sterile saline solution they are stored in loses its preservative effectiveness over time, even if the seal remains intact. The packaging seal itself may also degrade, allowing microscopic contaminants to enter and compromise the solution’s sterility.
Overworn lenses are those that have been used past their recommended replacement schedule, such as wearing a two-week lens for three weeks. Overwearing allows natural substances from the tear film, like proteins and lipids, to accumulate on the lens surface. This buildup is difficult to remove completely with standard cleaning solutions and causes the lens material to deteriorate, affecting its fit and function. The accumulated deposits and material breakdown significantly reduce the lens’s ability to transmit oxygen to the cornea.
Immediate and Long-Term Health Risks
Wearing old contacts introduces microbial threats and physically deprives the eye surface of oxygen. Compromised sterility from expired packaging or the protein buildup on overworn lenses creates an ideal breeding ground for harmful microorganisms, including bacteria, fungi, and the parasite Acanthamoeba. These pathogens can cause microbial keratitis, a painful and rapid infection of the cornea that can result in corneal scarring and vision loss if not treated immediately.
Oxygen Deprivation (Hypoxia)
When an overworn lens restricts oxygen delivery, the cornea suffers from corneal hypoxia (oxygen deprivation). A deteriorated or coated lens acts as a barrier, causing the tissue to swell, known as corneal edema. Chronic oxygen deprivation can trigger neovascularization, where new, fragile blood vessels grow into the clear cornea. This ingrowth of blood vessels can permanently obstruct vision and compromise the structural integrity of the cornea.
Physical Damage and Inflammation
Physical damage is another serious risk, as expired lenses can dry out, and overworn lenses become stiff or coated in rough deposits. These compromised lenses can rub against the corneal surface, causing tiny scratches called corneal abrasions. An abrasion allows pathogens harbored on the lens to penetrate the eye tissue and form a corneal ulcer.
Chronic protein buildup on the lens surface can also lead to an inflammatory response called Giant Papillary Conjunctivitis (GPC). GPC causes the inner surface of the eyelid to develop small bumps, or papillae, resulting in severe discomfort, itching, and an inability to wear contact lenses comfortably.
Proper Handling and Replacement Schedules
Protecting eye health begins with strictly adhering to the replacement schedule prescribed by an eye care professional, whether the lenses are daily, bi-weekly, or monthly. The replacement timeline is determined by the lens material and design, not by how often the lens was actually worn. A monthly lens must be discarded after 30 days regardless of usage. This practice prevents the accumulation of tear film deposits that lead to material breakdown and reduced oxygen flow.
Lens Hygiene for Reusable Lenses
Proper lens hygiene is equally important for reusable lenses, requiring the use of fresh contact lens solution every time the lenses are stored. Reusing or “topping off” old solution significantly reduces its disinfecting power. Lenses should be cleaned using the recommended “rub and rinse” method with the solution before storage to mechanically remove surface deposits.
The contact lens case itself can become a source of contamination and should be rinsed with fresh solution after each use, allowed to air-dry, and replaced entirely at least every three months.
Avoiding Water Exposure
A safety rule involves avoiding all contact between lenses and any form of water, including tap water, swimming pool water, or saliva. Non-sterile water sources can contain harmful microorganisms. Lenses should always be removed before showering, swimming, or using a hot tub, and only sterile contact lens solution should be used for cleaning and storage.