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Patient compliance a barrier to reducing risk of contact lens-associated infections
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It is estimated that just more than 40 million Americans and about 125 million people worldwide wear contact lenses. In the U.S., this is just more than 11% of the population.
Contact lens wearers thus greatly outnumber the 600,000 people or so who undergo laser corneal refractive surgery each year. The average age of a contact lens wearer is 31 years in the U.S., whereas the average age of the LASIK/PRK patient is now 39 years.
Every year about 3 million contact lens wearers become contact lens intolerant or electively discontinue contact lens wear, and many if not most of the patients who elect corneal refractive surgery come from this group. These numbers suggest that five of six patients who discontinue contact lens wear return to wearing glasses rather than opting for laser corneal refractive surgery. This finding has always surprised me, but it may be influenced in part by the fact that contact lens fitters and corneal refractive surgeons are two distinctly separate groups with different perspectives on refractive error correction. Many of the patients who discontinue contact lens wear do so after they develop one or more ocular surface or corneal complications.
The most feared and sight-threatening of these is infectious keratitis, with the potential for corneal ulceration, perforation and permanent scarring. A rough guideline is that five in 10,000 contact lens wearers will develop a corneal infection each year. This is about 20,000 patients per year in the U.S. and 60,000 globally. In the U.S., this represents about 50% of the infectious corneal ulcers diagnosed each year. To put this in perspective, the incidence of endophthalmitis after cataract surgery is approximately one per 1,000, resulting in 3,600 sight-threatening infections a year in the U.S.
From a public health perspective in regards to “iatrogenic” infection, contact lens wear is a significant issue. Several factors influence a patient’s risk of developing a contact lens wear- associated infection. The type of contact lens wear is a significant factor. While the overall rate of infection is about five per 10,000, according to a major study performed in Australia and supported by the Institute of Eye Research in New South Wales and Ciba Corp., with daily disposable contact lens wear this is reduced to 0.9 per 10,000, and with daily wear with patient sterilization and reuse, 3.1 per 10,000 for soft lenses and 4.5 per 10,000 for rigid gas permeable lenses. This suggests that our current methods of contact lens sterilization are imperfect or that patients are poorly compliant with the recommended regimens.
While both play a role, I suspect that poor patient compliance is the biggest issue. Many patients rinse their contacts in tap water, shower or swim with them in place, and do not follow the cleaning regimens recommended for the lenses and their storage cases. These bad habits also put them at risk for the more devastating waterborne infections secondary to Pseudomonas aeruginosa and Acanthamoeba. It remains the responsibility of physicians and contact lens fitters to do our best to educate our patients regarding proper contact lens and storage case cleaning and appropriate personal hygiene habits. The most common methods of contact lens sterilization remain multipurpose solutions and hydrogen peroxide, neither of which is effective against these two waterborne pathogens.
Advancements in the area of contact lens care and sterilization would be welcome, but poor patient compliance will likely trump any system the contact lens industry can develop.
Unfortunately, extended wear, which enhances the convenience of contact lens wear, also carries a higher risk. In the Australian study, the 0.9 per 10,000 risk with daily disposable soft lenses increased to 11.7 per 10,000 with extended wear soft lenses and to 19.3 per 10,000 with extended wear silicone hydrogel lenses. These risks deserve to be discussed with patients.
An interesting and perhaps somewhat unexpected finding was that the increased oxygen permeability associated with silicone hydrogel contact lenses did not reduce infection rates for daily or extended wear.
There is a real need to do all we can to reduce the risk of contact lens-associated infections, and the U.S. Food and Drug Administration deserves our compliments and support in its efforts to bring together ophthalmologists, optometrists, scientists, infectious disease experts and industry in a search for plausible solutions. Contact lens wear remains a safe, effective and popular option for patients with refractive errors who are seeking reduced dependence on glasses.
It is probable that the contact lens industry working together with dedicated consultant doctors and scientists will develop ever safer and more effective contact lens materials and sterilization methods, but the challenge of poor patient compliance will likely remain with us forever. While frustrating, every health care professional who deals with contact lens wearers needs to continuously remind them to properly care for their lenses and their eyes.