About Extended Wear Contact Lenses
The Food and Drug Administration (FDA) first approved certain contact lenses for overnight wear in 1981. Also known as continuous wear contact lenses, extended wear contact lenses are often made from soft materials. However, rigid lenses may be worn overnight for a vision correction procedure known as orthokeratology.
According to the American Optometric Association, 15 percent of contact lens users wear extended wear soft lenses. Extended wear contact lenses are intended for overnight wear for up to 6 consecutive nights. Lenses made from newer materials, such as silicone hydrogels, allow for up to 30 consecutive nights of continuous wear.
Contact Lens Risks: Microbial Keratitis
Microbial keratitis, also known as bacterial keratitis, is an infection of the cornea. Two types of bacteria are commonly associated with microbial keratitis, including Pseudomonas aeruginosa and Staphylococcus aureus.
Microbial keratitis is the most serious and sight-threatening complication associated with wearing contact lenses overnight. As more people choose to wear contact lenses, incidences of microbial keratitis continue to increase. An estimated 30,000 cases of microbial keratitis occur annually in the United States.
In 1989, the Microbial Keratitis Study Group found that wearing contact lenses overnight may increase the risk of developing microbial keratitis by 10 to 15 times, compared to daily wear lenses. According to the Centers for Disease Control and Prevention (CDC), symptoms of bacterial keratitis include:
- Eye pain
- Eye redness
- Blurred vision
- Sensitivity to light
- Excessive tearing
- Eye discharge
The risk of microbial keratitis from overnight wear of soft contact lenses is 13 to 20 out of 10,000 people. Vision loss occurs in 28 out of 10,000 people as a result of microbial keratitis.
In 2004, the American Academy of Ophthalmology issued a safety statement about the risks associated with extended wear of contact lenses, which was most recently updated in 2013. The FDA has also advised that overnight wear increases the risk of infection.
In 2009, Ophthalmology published a case-controlled study comparing branded lenses. Researchers found lenses made by Bausch & Lomb were less likely to cause microbial keratitis in comparison to Johnson & Johnson's Surevue and Acuvue 2. Acuvue 2, a low-cost lens, is a popular option in the United States.
Other microbial keratitis complications include a peripheral corneal scar. Though the scar does not cause vision loss, it still represents a permanent injury. Individuals with peripheral corneal scarring are unable to have corrective LASIK surgery, among other impacts.
Treatment Options In A Growing Market
The use of overnight contact lenses has increased in the past three decades. Unfortunately, awareness of the risks remains minimal. The industry continues to develop innovation, such as the incorporation of oxygen permeable silicone hydrogel lenses, but the risk of infection still exists.
Treatment for microbial keratitis may be costly. Depending on the severity of the infection, treatment options include topical antibiotics, subconjunctival antibiotics, or soft contact lenses soaked in antibiotics. There is also the option of systemic therapy, collagen shields, or topical corticosteroid therapy, as well as a corneal transplant or patch grafts.
Though millions of Americans wear contact lenses, FDA statistics show the number more than doubles to nearly 100 million worldwide. Globally, the contact lens market brought in $8.95 billion in 2015. The value of the contact lens market is expected to grow, reaching $12.5 billion in 2020.
Understanding potential complications related to extended wear contact lenses is the best way to mitigate risks. If you have developed microbial keratitis from overnight lens wear, you're not alone.