Contact lenses are regulated as medical devices, and their safe use is strictly tied to two timelines: the manufacturer’s expiration date on the sealed packaging and the prescribed wear schedule after opening. Ignoring either timeline significantly increases the risk of eye health complications, which can range from minor irritation to severe infections. Understanding both types of expiration is necessary for maintaining clear vision and protecting eye health. The integrity of the lens material and the sterility of the packaging solution are only guaranteed up to the printed date.
Locating Manufacturer Expiration Dates
The first type of expiration to check is the literal, printed date on the product packaging, which applies to sealed lenses and solution. This date indicates the maximum time the product is guaranteed to be sterile and effective. You can find this date, often labeled “EXP,” on the outer box, the individual foil-sealed blister packs, and contact lens solution bottles.
The date format is typically year and month (e.g., YYYY-MM or YYYY/MM), meaning the product is safe to use until the last day of that specified month. After this date, the saline solution the lens is suspended in can lose its sterility or become compromised if the airtight seal degrades. This degradation can allow contamination from bacteria or fungi, which are often invisible.
Contact lens solution bottles have a second expiration rule that applies once the bottle is opened. The chemical preservatives and disinfectants in the solution begin to lose effectiveness after exposure to air and contaminants. Most manufacturers recommend discarding the solution within 90 days of opening, regardless of the printed expiration date. To follow this rule, use a permanent marker to write the discard date on the bottle immediately after opening.
Recognizing Over-Worn Lenses
The second type of expiration relates to the lens material itself after the package is opened and the prescribed wear schedule has been exceeded. This schedule is dictated by the lens type, such as daily, bi-weekly, or monthly replacement. Wearing a lens beyond its intended lifespan is known as overwear, which causes predictable changes in the lens material and comfort.
One of the first signs of overwear is increased discomfort, which may feel like dryness, irritation, or a foreign body sensation. Over time, the lenses accumulate protein, lipid, and calcium deposits naturally present in tears, leading to cloudiness or a noticeable film on the surface. These deposits make the lens less clean, even after using solution, and can reduce visual clarity, causing blurred vision.
The physical integrity of the lens also degrades, which can manifest as minor tears, nicks, or a feeling that the lens is becoming stiff or brittle. The lens material begins to lose its ability to transmit oxygen to the cornea, a process called oxygen permeability. This loss of function is not immediately noticeable but is a significant factor in eye health deterioration.
Potential Health Consequences
Using lenses past either their sealed expiration date or their prescribed wear schedule introduces serious risks to the delicate tissues of the eye. The main danger from expired, sealed lenses is contamination from bacteria or fungi that compromised packaging may have allowed to enter. This contamination can lead to severe infections like bacterial keratitis, which is a painful inflammation of the cornea.
Over-worn lenses pose a dual threat: they harbor a higher bacterial load due to deposit buildup, and they restrict the flow of oxygen to the cornea. A lack of sufficient oxygen, known as corneal hypoxia, can cause blood vessels to grow into the clear cornea to compensate for the deprivation. This condition is called neovascularization and can permanently affect vision.
The buildup of debris on over-worn lenses can also trigger an inflammatory response on the inner surface of the eyelid, resulting in giant papillary conjunctivitis (GPC). Unchecked infections or significant corneal damage, such as a corneal ulcer, can result in permanent scarring of the cornea. This scarring can severely impair vision and, in the most serious cases, lead to permanent vision loss.