Contact lenses are convenient, but their use can present significant ocular risks to those who wear them. Medscape interviewed Bernard P. Lepri, OD, MS, MEd, an optometrist and clinical review scientist, and Michelle Tarver, MD, PhD, an ophthalmologist and epidemiologist, both in the Office of Device Evaluation at the US Food and Drug Administration (FDA), about the risks associated with contact lenses, including what signs and symptoms to be aware of, as well as the importance of reporting problems related to their use to the FDA, with instructions on how to do so.
Adverse Events to Watch For
Medscape: We could categorize the risks associated with contact lens wear according to: (a) the way in which they are manufactured, including material and composition; (b) contact lens hygiene, including products used in their care; and (c) contact lens wear, including improper fit and/or inappropriate wearing schedules. Can you describe some of the adverse events associated with each?
Dr. Lepri: A red eye is hallmark for many of the different categories of adverse events that may occur. Other symptoms are irritated eyelids, itching, burning, pain, and decreased vision. They may come from the contact lens, from the care products, and from the hygiene habits of the contact lens wearer. The most worrisome adverse event is infectious corneal ulcers, also called microbial keratitis. These conditions can develop quickly, can be serious, and, in rare cases, can cause blindness. Bacterial conjunctivitis or fungal keratitis (both types of microbial keratitis) can occur as a result of poor hygiene or contamination of the contact lens care products. Adverse events also include any type of conjunctivitis. For example, allergic conjunctivitis can develop in patients allergic to an ingredient in the contact lens care products or the contact lenses.
The levels of risk are also dependent on the contact lens type. Daily-wear lenses have lower risk for adverse events compared with extended-wear lenses, and, of course, that can be further subdivided into the types of materials used. A study from Australia evaluated the incidence of microbial keratitis as well as the rates of microbial keratitis among various modes of contact lens wear (daily wear, daily disposable, and extended wear) and types of contact lens materials (conventional hydrogel, silicone hydrogel, and gas permeable). They found that 7.5% of wearers were using daily disposable contact lenses and 9.3% were using silicone hydrogel contact lenses. The annual incidence of all contact lens-related microbial keratitis was 4.8 per 10,000 wearers. According to this study, the annual incidence of moderate and severe or culture-proven keratitis in:
Daily disposable contact lens users was 0.9 (0.7-1.3),
Daily-wear soft contact lens users was 3.1 (2.9-3.3);
Daily-wear silicone hydrogel contact lens users was 4.5 (3.5-6.4);
Extended-wear soft contact lens users was 11.7 (8.2-20.6); and
Extended-wear silicone hydrogel contact lens users was 19.3 (13.9-31.3).
Good hygiene is critical in reducing the risk for adverse events. It is imperative that contact lens care be done in a clean environment with clean hands. The contact lens case must be clean and hygienic as well. Every time contact lenses are used and disinfected, the case should be cleaned out, too; rinse it out and let it air-dry. Never add (or top off) solution to the case. If you top off the solutions in your case, then you are essentially disinfecting your lenses with a diluted solution. You have to have the maximum concentration at all times. A clean, lint-free towel should be used so as not to transfer bacteria from your hands to the lenses. You want to avoid the opportunity for bacteria or other microorganisms to multiply and grow, because if the conditions are right, they can cause an infection.
Improperly fitting contact lenses can potentially contribute to the development of an adverse event. Lenses that are too tight can cause oxygen deprivation to the cornea, resulting in corneal edema, and cause a great deal of discomfort. If the physiology of the cornea is compromised by an improperly fitting lens, an infection could develop. Poorly oxygenated corneas can also develop neovascularization, a growth of small, fragile vessels that encroach from the periphery of the cornea towards the center. The cornea does not have any blood vessels in it. These new vessels then can contribute to the cornea losing its clarity if any inflammation or infection develops. These vessels are very fragile, and if bleeding should occur, the cornea will become cloudy.
We emphasize that patients should always maintain the wearing schedule as designed and recommended by their eye care professional. If you're prescribed daily-wear lenses, you should only wear them during the day for the recommended number of hours. Eye care professionals establish a wearing pattern and make a recommendation to their patients, but patients don't always follow it. Wearing the lenses longer than the recommended time may cause swelling of the cornea or overwear syndrome.
Medscape: What problems with contact lenses would the FDA like eye care professionals to report?
Dr. Lepri: We would like eye care professionals to report any untoward event experienced by the wearer. This includes eye irritation that requires the eye care professional to recommend switching brands, because eye irritation can be associated with the lens material, its manufacturing, or care products being used with a specific type of lens. We also want infections reported, including microbial keratitis.
Unfortunately, most practitioners think that these events are typical and are expected when wearing contact lenses. However, the important thing for us to emphasize to them is that if you notice a certain event occurring in your patients, you don't know for sure whether it's associated with the contact lens itself, the care products being used, or how the patient is using the care products. If you report a problem to the FDA and we happen to be receiving reports from numerous other practitioners around the country about the same products, when we analyze the data we can establish whether there's a trend or a safety issue. If there is, then we can notify the professional community, the manufacturers, and the public.
This is why it's so important to report events that occur with contact lenses and to not assume that it's just to be expected because it's a contact lens. We understand that it is difficult at times to determine whether any of these adverse reactions are due to the lens. The FDA has staff dedicated to better understanding the role of devices in adverse events, and the more information that we receive, the better able we are to determine the primary cause of contact lens-related adverse events. One person's adverse event in the office could be a signal for the FDA to look more closely at other events that are being reported and see if we can establish any trends.