Letters to the Editor
Soft Bifocal Lenses and Myopia Progression
I enjoyed reading the Pediatric and Teen CL Care column from March 2009 titled, "Soft Bifocal Contact Lenses for Myopia Progression," by Jeffrey J. Walline, OD, PhD, and Marjorie J. Rah, OD, PhD. I applaud the research being conducted on using soft bifocal lenses to retard the progression of myopia. I have used this same technique in my private practice since 1995. Currently, I fit almost all of my progressing myopes with these contact lenses.
At the American Academy of Optometry meeting in 2001, I presented a Case Study Series poster that quantified almost six years of experience with this modality. The study population included 60 subjects, aged 11-to-37 years, with myopia >−1.00D (mean −3.53D ±2.04D) and no more than 0.50D cylinder. Subjects were studied for 0.7 to 5.5 years (mean 2.2 ±1.2 yrs). The rate of myopic progression prior to fitting was −0.50 ±0.37 diopters/year, which decreased to 0.00 ±0.07 diopters/year following the soft bifocal contact lens fits. This compared to Aller and Grisham's (2000) study, which also found myopic progression of −0.50 diopters/year prior to treatment, which decreased to 0.08 diopters/year after treatment.
Age of entry into the study did not affect the outcome. The longer a patient had myopia prior to the study, the more effective the reduction in progression. In this study, there was no correlation of phorias to myopic progression before or after the initiation of soft bifocal lenses.
The mechanism for this beneficial effect remains unclear — perhaps it results from altering peripheral focus, perhaps from altering accommodation, or perhaps from altering visual effects of environmental stimuli. Nonetheless, it is truly exciting to clinically witness the reduction of myopic progression following soft bifocal contact lens fitting.
Susan G. Rodgin, OD, FAAO
Responding to "Glasses or Contact Lenses for Young Patients?"
I think Dr. Rah and Dr. Walline were too kind in their response to Dr. Walkowiak's Letter to the Editor titled, "Glasses or Contact Lenses for Young Patients?" (May 2009). Does Dr. Walkowiak not believe that new products and instrumentation make any difference in how we practice and how we make decisions and recommendations from 20 years ago? I have been in practice for 35 years. Although I've never worked with the foremost experts in contact lenses, for about 20 years I have been fitting kids 8 years old or younger — if the situation dictates it — with contact lenses. I have been able to follow most of these patients into adulthood and have not seen all of the dire consequences that Dr. Walkowiak implied. I believe he needs to shed his myopic views as they pertain to patient maturity and responsibility.
Ronald J. Anderson, OD
Battle Creek, Mich.
A Caution Against Peroxide Use
I read with great interest the June 2009 Point/Counterpoint column on the topic of "Hydrogen Peroxide Versus MPS" by Charlotte Joslin, OD, PhD, and Craig A. Woods, PhD, FAAO. As a 25-year practitioner, my experience weighs heavily against hydrogen peroxide use for most patients. My reasons are simple.
First, as Dr. Joslin correctly points out, only the two-step peroxides have "total efficacy." She fails to mention that the common, commercially available systems are essentially one-step. Dr. Woods is correct here: peroxides offer virtually no disinfection after 30 minutes of lens immersion. This issue is well documented in the 2001 paper by Hughes and Kilvington, which should be read by any peroxide advocate.
My second argument against peroxide use is a practical one. In the 1980s and early 1990s, our practice averaged two cases per month of accidental ocular exposure to full-strength peroxide. These cases were mostly minor in severity, but usually resulted in a lost day of work or school for the suffering patients. Noncompliance is one thing, but this type of human error is especially unforgiving. Peroxide toxicity is a ridiculous hazard for our patients, against which I would accept any degree of Andrasko Grid-type corneal staining issues.
I would also suggest that severe infections are not as strongly associated with peroxide because this agent holds a small minority share of the solution market.
In summary, my patients and I continue to benefit from the use of polyquad/Aldox-based solutions, with the biguanide products used as distant secondary choices. I reserve peroxides for patients who have multiple sensitivities and insist on wearing reusable contact lenses.
William B. Potter, OD
Hamilton Square, N.J.
Dr. Potter has previously received honoraria and travel funding from Allergan, Alcon, and CIBA Vision.
Dr. Joslin's Response
I appreciate the careful reading and comments by Dr. Potter regarding my recent hydrogen peroxide Point/Counterpoint article, and welcome the opportunity to further discuss this common misperception on the efficacy of onestep peroxide systems versus multipurpose solutions.
No doubt, two-step hydrogen peroxide systems have superior efficacy against Acanthamoeba: this is evident not only in the older Hughes and Kilvington literature, but also in our recent paper examining solution efficacy against recent Acanthamoeba clinical and tap water isolates (Shoff, 2008). As pointed out in the Point/Counterpoint article, only a simulated two-step system had total efficacy against recent Acanthamoeba isolates (at 24 hours). What was not described is that the same study also evaluated the efficacy against Acanthamoeba of a common one-step peroxide system in addition to four universal multipurpose systems (including both polyquad/Aldox- and biguanide-based disinfectants). MPS systems tested had complete or nearly complete survival of Acanthamoeba isolates following exposure to the disinfectant, regardless of a six- or 24-hour soaking period; trials with viable Acanthamoeba isolates for each MPS system: 90/90 (100 percent), 90/90 (100 percent), 90/90 (100 percent), 85/90 (94.4 percent). In comparison, only 49/90 (54.4 percent) of trials had viable Acanthamoeba isolates with the tested one-step peroxide system. This indicates that even one-step peroxide systems offer some disinfection against Acanthamoeba.
So this begs the question: is the brief disinfection that occurs in the first hour before neutralization with one-step peroxide systems adequate enough to overcome organisms, resulting in a superior protection compared to existing multipurpose systems? Results from our laboratory and epidemiologic studies, which account for solution prevalence in the population through use of controls, seem to suggest that this may be the case, although the outbreak of Acanthamoeba keratitis persists and is occurring with all existing solutions.
This circles back to one of my original points, which I think is consistent with Dr. Potter's observation: education regarding patient hygiene is critical, and this includes appropriate instruction with peroxide systems. After 15 years in the field, I have fortunately never seen two cases per month of a peroxide-induced keratopathy — but we are now seeing at least two cases per month of Acanthamoeba keratitis. Reintroduction of two-step peroxide systems may not be a bad thing.
Know Your EFAs
I was very impressed with the July 2009 Research Review article titled, "Essential Fatty Acids and Dry Eye: What Do We Know?" by Lyndon Jones, PhD, FCOptom, FAAO. He did an excellent job discussing the role of nutrition in the dry eye disease process.
I only hope that readers do not stop halfway through the article and take away a concept that omega-3s are "good" and omega- 6s are "bad." Dr. Jones made an excellent point that both of the fatty acids are essential and needed in the correct balance to maintain overall health, including a healthy tear film. I've found GLA (an omega-6) in addition to other nutrient co-factors to be very effective in treating dry eye and meibomian gland dysfunction.
Toward the end of the article Dr. Jones mentions that some of the fish oils might be contaminated with methyl mercury or pesticides. While I'm sure that TheraTears Nutrition (Advanced Vision Research) is an excellent product, it should be known that all fish oils entering the United States are screened for PCBs and other contaminants, so U.S. consumers can rest assured that all fish oils are safe. Consumer Labs, an independent nutritional product testing organization, recently tested dozens of fish oil products and found that none of them had contaminants.
Jeffrey Anshel, OD, FAAO
President, Ocular Nutrition Society
To obtain references for these letters, please visit http://www.clspectrum. com/references.asp and click on document #165.
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Contact Lens Spectrum, Issue: August 2009