Extended wear contact lenses (EWCLs) are approved for continuous use, including overnight wear, for a limited number of days. EWCLs offer users the convenience of waking up with clear vision without daily handling. They are typically made from silicone hydrogel, a material that allows significantly more oxygen to pass through to the cornea. While technological advances have improved their safety profile, wearing any contact lens overnight carries a higher risk of ocular complications than removing them daily. EWCLs are considered safe only when users adhere precisely to the wearing schedule and hygiene instructions provided by their eye care professional.
Why Extended Wear Lenses Carry Higher Risk
EWCLs carry an elevated risk due to reduced oxygen supply and the continuous presence of the lens on the eye’s surface. The cornea relies primarily on oxygen absorbed from the air to maintain its health. When the eyes are open, EWCLs made from highly breathable silicone hydrogel allow sufficient oxygen to pass through.
When a person sleeps, the eyelid covers the cornea, naturally reducing the oxygen supply. Wearing a contact lens further restricts this flow, leading to a state called corneal hypoxia. Hypoxia stresses the corneal cells, making the eye less able to fight off potential infections and increasing the risk of inflammation.
Furthermore, the constant presence of the lens prevents the eye’s natural processes from effectively flushing away debris, proteins, and dead cells that accumulate on the lens surface and beneath it. This continuous layering creates a warm, moist, low-oxygen environment highly conducive to microbial growth. Bacteria can adhere to the lens, forming a biofilm, which compromises the eye’s natural defenses and raises the risk of severe eye problems.
Recognizing Warning Signs and Serious Complications
Misuse of EWCLs or the onset of a complication can lead to serious symptoms that require immediate attention. The most significant concern is microbial keratitis, a sight-threatening infection of the cornea. The risk of developing this condition is estimated to be 10 to 15 times greater for those who sleep in their lenses compared to those who wear them only during the day.
Signs that something is wrong include excessive eye redness, pain, or discomfort that does not resolve quickly after lens removal. Other indicators are blurred or hazy vision, a gritty sensation, increased sensitivity to light (photophobia), or discharge from the eye. A clear sign of a worsening infection is the appearance of a white or grayish spot on the cornea itself.
Any of these symptoms should prompt the user to remove the lenses immediately and seek urgent consultation with an eye care professional. Ignoring even mild irritation can allow a condition to progress rapidly into a severe corneal ulcer, which may lead to permanent vision damage or loss if left untreated.
Strict Guidelines for Safe Use
Minimizing the risks of EWCLs depends entirely on strict adherence to professional guidance and product limitations. Users must never exceed the maximum wear duration prescribed by their eye doctor, which is typically six nights and seven days, or sometimes up to 30 continuous days for certain lens types. Attempting to stretch the use of a lens beyond its approved cycle increases the accumulation of deposits and debris, which compromises eye health.
Even if a lens is approved for continuous wear, many eye doctors recommend removing the lenses at least once a week for thorough cleaning and disinfection, providing the cornea a necessary break.
Hygiene and Replacement Rules
- Remove lenses at least once a week for thorough cleaning and disinfection, even if approved for continuous wear, to provide the cornea a necessary break.
- Use only fresh, approved contact lens solution for cleaning and disinfection; tap water or saliva should never be used.
- The lens replacement schedule, whether monthly or bi-weekly, must be followed precisely.
- Lenses should be discarded as directed, not worn past their expiration.
- Never sleep in a lens that has not been explicitly approved for extended or overnight wear, as these lenses lack the necessary oxygen permeability.
Regular eye doctor check-ups are required, often more frequently than for daily wear users, to monitor the health of the cornea. These exams allow the doctor to detect silent threats, such as early signs of corneal swelling or the growth of new blood vessels (neovascularization) due to chronic hypoxia.