letters to the editor
Consider This Soft Lens Replacement Schedule
I enjoyed the Point/Counterpoint article in the June 2010 issue on the topic of Lens Replacement Frequency by Colleen Riley, OD, MS, FAAO, and Peter Bergenske, OD, FAAO. Replacement compliance continues to be an ongoing problem for contact lens practitioners and patients. I believe that both Dr. Riley and Dr. Bergenske provide evidence to defend their respective positions for different lens replacement schedules.
One replacement interval for frequent replacement contact lenses that always seems to be ignored is weekly replacement. Why have none of the four major contact lens companies developed a contact lens specifically for weekly replacement? I have posed this question to many of my colleagues, contact lens reps, and members of the contact lens industry. I have never received any answers as to why this cannot be accomplished. Is it a problem with the manufacturers not being able to package an easy number of lenses, such as a six-pack?
Outside of daily disposal, I believe a weekly replacement schedule would clearly be the best choice for replacement compliance (i.e., easier to remember when to throw out the lenses). I think most contact lens practitioners would agree that a lens replaced more frequently will be more comfortable and less likely to cause ocular health problems. If contact lens manufacturers can produce affordable daily disposable lenses, they certainly should be able to manufacture a safe, comfortable, weekly replacement soft contact lens at a decent price point. soft contact lens at a decent price point.
I found it highly ironic that on the page preceding this Point/Counterpoint article was Dr. Jason Nichols' Editor's Perspective titled "It's Time for All of Us to Step Up." Dr. Nichols writes, "industry must launch new products that not only meet patient needs, but also create even more interest in wearing contact lenses." I think a weekly replacement contact lens would perform better than either monthly or two-week replacement lenses and would result in better replacement compliance. I believe that patients, practitioners, and lens manufacturers could benefit from this type of lens. Or do we continue to use the same old two-week contact lens replacement cycle that has been used since 1987?
Patrick J. Wellik, OD
Apple Valley, Minn.
Responding to MK Article
I read with interest the article "A Closer Look at Microbial Keratitis" in the August 2010 issue by Aaron Zimmerman, OD, MS, FAAO, and Jason Nichols, OD, MPH, PhD, FAAO. However I would like to point out several issues with the article that your readers may find of interest.
The incidence of microbial keratitis (MK), specifically bacterial keratitis, that was quoted is grossly underestimated, and here's why. The vast majority of cases of bacterial keratitis in the United States are treated by private practice doctors, like myself, and are never reported to the U.S. Food and Drug Administration. Conversely, most of the studies quoted in your article were based on the experience of University Eye Centers or large corneal referral centers and represent cases of treatment failures, mixed etiology, etc.
I also know that this is true because I see at least 30 cases of bacterial keratitis per year. (I have a small contact lens practice but a medium-sized medical eye practice.)
As one result of under-reporting, we continue to have contact lens manufacturers and many practitioners advertising "safe" contact lenses. In private practice, they're not.
I would like to also stress that because community-acquired methicillin-resistant Staphylococcus aureus represents 40 percent of current ocular pathogens (Asbell et al, 2009), culturing with antimicrobial sensitivities is critical before starting treatment, in contrast to the American Academy of Ophthalmology's recommendation quoted in your article that advises to perform a culture for a non-responsive lesion or if there is extensive infiltration into the stroma.
It is well known in clinical practice that once antibiotic treatment is started, it is notoriously difficult to get a corneal (or conjunctival for that matter) sample to grow out on culture.
While identification of the organism is important, what is of highest concern is to what antibiotic is the organism sensitive? Practitioners who continue to treat empirically with fluoroquinolones will find their treatment failures increasing.
Also, you failed to mention the importance of trimethoprim in cases of MRSA.
In my opinion, most of the research regarding contact lens disinfection and cleaning with multipurpose solutions is biased, lacks credibility, and is not applicable to the real world, as was painfully illustrated by the recent outbreaks of fungal and Acanthamoeba keratitis as well as the ongoing bacterial infections.
Multipurpose solutions simply don't work well. They certainly don't clean, yet we and the contact lens industry continue to prescribe them or to "sell" the consuming public on their "safety" or extoll the virtue of "convenience" to the detriment of our own reputation and the safety of our patients.
Yet, during the last several years of ongoing debate, not once have I seen in print the obvious suggestion that we prescribe a separate detergent surfactant cleaner for patients who re-use their lenses. Wouldn't this be potentially more valuable than the ongoing "rub versus no-rub" debate?
The tail appears, again, to be wagging the dog.
Mark R. Flora, OD
Dr. Zimmerman's and Dr. Nichols' Response: We thank Dr. Flora for his letter and appreciate the opportunity to respond to his comments regarding our recent article on microbial keratitis.
Incidence of Microbial Keratitis The incidence of microbial keratitis (MK) has been thoroughly investigated for more than 20 years, and the estimated rate of infection as well as risk factors have not significantly deviated over that time period (Poggio, 1989; Seal, 1999; Cheng, 1999; Lam, 2002; Schein, 2005; Stapleton, 2008). These studies have been performed in multiple geographic locations around the world, and although they do differ in their methodology, they have all yielded relatively consistent estimated rates of MK.
One concern raised by Dr. Flora was in regard to how the data from the studies were acquired. While it is true that some of these studies were based in large hospital settings (which tend to attract more severe disease and can often overestimate actual rates of disease), a few were surveillance studies in which eye-care practitioners in a specific region reported all encountered cases of MK during a specified period of time. Telephone surveys of the general population were also performed to estimate the frequency of contact lens wear for those regions (Stapleton, 2008; Cheng, 1999). The estimated incidence of MK could therefore be calculated. Additionally, patients with confirmed MK were interviewed to assess risk factors.
The actual number of individuals who have MK may never be known, but numerous studies give eyecare practitioners a reasonable estimate. Some eyecare practitioners may encounter more cases of MK than others would, particularly if that practitioner works in an anterior segment referral center or a high-volume contact lens practice. These variances among individual practitioners are why it is important that a carefully conducted epidemiological evaluation be performed.
MRSA and Effective Treatments Dr. Flora commented that methicillin resistant Staphylococcus aureus (MRSA) is becoming much more frequent in the United States. It is of interest to note that a recent article shows some evidence that hospital-associated MRSA (HA-MRSA) is slightly on the decline—at a rate of more than 9 percent per year during this period (Kallen et al, 2010). However, community-associated MRSA (CA-MRSA) is increasing rapidly and will certainly be an increasing cause of bacterial keratitis (Blomquist, 2006). Contact lens patients may be more susceptible to CA-MRSA as they frequently touch their eyes and, of course, contact lens patients vary in their compliance with lens care and wear habits, which might also contribute to increased risk for infection.
Trimethoprim is a very formidable treatment for MRSA. Trimethoprim inhibits successive steps in the folate synthesis pathway, making folic acid unavailable for DNA replication (Bartlett and Snyder, 2010). The Ocular TRUST studies have shown that nearly 95 percent of MRSA cases are susceptible to this medication, while fluoroquinolones are only 18 percent to 30 percent effective (Asbell, 2008).
Although fluoroquinolones are not fully effective against MRSA, they are broad-spectrum, are nearly as effective as fortified antibiotics (Shah, 2010), and they constitute the recommended initial treatment of MK according to the American Academy of Ophthalmology (Rapuano, 2008). Another chloro-fluoroquinolone not originally mentioned in our article is besifloxacin (Bausch + Lomb). The use of besifloxacin for MK is currently off-label, but initial studies show that it is currently effective against MRSA (Ward, 2007). If, however, the initial fluoroquinolone treatment fails, the use of trimethoprim in unresponsive ulcers is indicated, particularly those in which MRSA is the infectious organism (Melton, 2010).
Vancomycin is another antibiotic that is typically effective in eradicating MRSA infections and is commonly used in a fortified concentration (Rapuano, 2008).
The importance of culturing cannot be overstated. It is clearly effective in determining the appropriate treatment. It takes time for a culture to incubate, and any form of keratitis needs to be treated immediately. Therefore, a recommended initial treatment guideline similar to the American Academy of Ophthalmology's, while not perfect, will lead to successful treatment for the majority of cases.
Contact Lens Solutions Dr. Flora's comments about lens care solutions based on his personal experiences are interesting. Multipurpose care solutions do not sterilize lenses, and it probably would not make much difference if they did, as microbes from an individual's hands are introduced during lens application. Even so, patient noncompliance with hand washing, case replacement, topping off and lens overwear are likely to continue. Regardless of patient receptiveness, eyecare professionals need to continually educate patients on proper compliance, as this could reduce nearly a third of the cases of MK (Keay, 2009).
The use of separate cleaning agents such as surfactants will certainly help clean the lens by removing debris, and depending on their composition, they may also contribute to active disinfection. Advancements with contact lens solutions are certainly welcomed, but rather than only eradicating microorganisms and debris, future care solutions may also need additional properties that enhance the normal ocular surface defense mechanisms.
Conclusion Contact lens wear is a risk factor for sight-threatening MK, however the risk of MK is low compared to other life-risks. Epidemiological studies need to continue as does development of better lens materials, solutions, and antimicrobials and basic research into the pathophysiology of MK in an effort to eradicate this complication.
For references, please visit www.clspectrum.com/references.asp and click on document #180.
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