Contact Lens SPECTRUM^®

 

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A Suggestion for Extended Wear

As a contact lens clinician and clinical investigator since 1977, I disagree with Dr. Nathan Efron’s premise in his June 2018 article “Current and Future Controversies in Contact Lenses” that the contact lens industry has failed three times at extended wear contact lenses. There is no question that extended wear lenses are far more convenient compared to daily disposable lenses, which have to be applied and removed daily.

Unfortunately, contact lens manufacturers have been conflicted. Originally, oxygen permeability was the limiting factor of extended wear. When this was improved, we saw problems with surface buildup and lens deposits as well as with noncompliance. To solve this issue, the industry went to planned replacement and eventually to daily disposables. However, to reduce the cost, they went back to HEMA and older, lower-Dk/L materials.

Newer daily disposable lenses manufactured in silicone hydrogel materials have increased oxygen permeability, but they also have an increased cost to the point that they are no longer affordable for many patients. This has added to the compliance issue with regard to replacement schedule. The occasional red eye and the even more rare ulcer usually result from noncompliance. Why has the industry not addressed this problem?

The obvious answer is to merge the two modalities by creating a three-day disposable lens—a highly oxygen-permeable lens that would be worn continuously for two nights and three days and removed on the evening of the third day. There would be no solution to purchase or to cause sensitivity, no protein buildup or coating, rare giant papillary conjunctivitis, freedom from maintenance for all but two times a week, and reduced cost compared to daily disposables because patients would need to buy fewer lenses. This would greatly improve compliance and reduce extended wear complications. It would also enhance contact lens companies’ bottom lines with additional sales of premium lenses.

Furthermore, the first company to have this modality would enjoy a monopoly as it would be one of a kind. We already have the product available. All that remains is the U.S. Food and Drug Administration (FDA) clearance and marketing. Sometimes the answers are right there in front of us if we just pay attention to our patients’ behavior

David J. Anderson, OD, Freeport, IL

Dr. Efron’s Response:

I thank Dr. Anderson for his interest in my article and for his thoughts on what we might call “regular replacement extended wear.” There are indeed some merits to his proposal. The classic “Gothenburg Study” (Holden et al, 1985) showed that more frequent replacement of extended wear lenses lessens their physiological impact. Also, as Dr. Anderson rightly points out, such a modality would be cost effective, which is a very important consideration, as (reduced) cost is a key aspect of any health care modality.

However, despite these perceived benefits, there is still a major problem with the concept of “regular replacement extended wear”—or with any other extended wear modality—and that is the requirement to sleep overnight in lenses. Without exception, every risk-analysis study of extended wear carried out over the past 30 years has arrived at exactly the same conclusion: the risk of microbial keratitis when sleeping in lenses is about six times greater than when wearing lenses during waking hours only. Although the absolute risks are small, the industry is hypersensitive to the notion of “increased relative risk” and is therefore averse to the notion of extended wear. Until we can somehow reduce this risk (and the answer is not at all obvious), the industry is likely to continue to place all of its eggs in the daily disposable basket.

On the question of compliance, I see no reason why lens wearers would be any more compliant with a three-day replacement schedule than with a two-week or four-week replacement schedule. A lens wearer might conclude: “If lenses are OK to be worn for three days straight, then I’m sure they would also be OK to wear for three months straight.”

Differing Thoughts on Orthokeratology and Myopia Control

Myth Buster I am writing in response to Professor Nathan Efron’s June 2018 article “Current and Future Controversies in Contact Lenses.” Overall, I found the article to be excellent and well-informed, which is to be expected given the distinguished career of the author. The exception is in the section on orthokeratology (OK), which falls short of the scientific rigor that has been applied throughout the rest of the article. This is perhaps understandable given the predominant focus on soft lens research throughout Prof. Efron’s eminent career. However, it does unfair disservice to OK and to the important role that this modality has, both in helping slow the progression of myopia and in contact lens practice in general. Consequently, I would like the opportunity to debunk the myths that he has portrayed and to set the record straight.

Prof. Efron claims that OK is capable of reducing myopia by only about 2.00D, citing Carney (2010) in the 2nd edition of the medical textbook Contact Lens Practice. Through the filter of relying only on published peer-reviewed articles, this could be considered correct; however, in applying this filter, a measured awareness of what the filter blocks out also needs to be taken into consideration.

In this case, the peer-reviewed filter results in study participants being considered only when the refraction range falls within study entry criteria, which in OK studies is typically from around –1.00D to –4.00D (Charm and Cho, 2013; Chen et al, 2013; Cho et al, 2005; and others. Full list available at www.clspectrum.com/references ). The result is that the mean myopia across the study cohort ends up being around –2.00D. Therefore, the deduced –2.00D correction limit quoted by Prof. Efron is due to the peer-reviewed study design process, which is fundamentally different from OK not being capable of reliably providing anything more.

To dig further into this topic, we can turn to Charm and Cho (2013) who enrolled only children who had –5.00D or more myopia in their study investigating whether partial correction of myopia with OK slowed progression of myopia. The authors targeted partial correction of –4.00D across all study participants and reported a mean refraction change of 4.50D from OK. I would argue that this value is closer to the true capability of OK because the same correction target was applied to all subjects.

This study also provides an insight into the reliability of OK correction. Their reported median range of correction from –2.75D to –6.25D clearly indicates variation in effect given that all participants were targeted to correct –4.00D. Whether this is enough to brandish OK as being unreliable, however, is a different matter. The longevity of OK in clinical practice has allowed OK lens manufacturers the time and experience to develop comprehensive systems to support their respective designs. Outside of the constraints of scientific study design, practitioners are free to evaluate response from a few nights of lens wear and to alter lens design parameters toward correcting any residual refractive error.

Finally, even this study of Charm and Cho is now out of date. Various technology advances over recent years have led to considerable development in OK lens designs leading to reported, although admittedly not peer-reviewed, improvements in reliability for achieving full refraction correction with the first-fit lens (Gidosh et al, 2017).

On a different topic from Dr. Efron’s article, I’m not sure that anyone has ever promoted OK as a procedure to avoid contact lens wear, which thereby negates the suggestion of OK being only a psychological crutch.

With regard to soft lenses, I agree that they are amazing devices. I also believe that they represent one of our biggest failings as a profession for allowing the public to come to view this amazing technology as a simple commodity that can be readily exchanged among brands and purchased over the internet. OK lenses are more expensive initially compared to soft lenses, but over time, this cost is dissipated due to the longevity of OK lens life; this may result in a better average cost over time. Agreed, OK lenses are slightly more difficult to fit; but systems to aid their fitting are constantly improving, and there are an increasing number of empirical designs across the market for which the initial lens is calculated from corneal topography measurement. Corneal topography also provides the perfect transfer medium when practitioners need to seek expert advice; unlike soft lens fits that rely on subjective visual assessment, topography maps provide an accurate digital record of fit that can be sent anywhere in the world at a touch of a button.

In terms of infection risk, soft lenses, especially silicone hydrogels, haven’t been the hoped-for savior in terms of reducing microbial keratitis (MK). The risk of MK in overnight wear of either hydrogel or silicone hydrogel lenses (20 to 25 per 10,000 patient-wearing years) (Stapleton et al, 2008) is around twice as high as the risk in pediatric OK wear (13 per 10,000 patient-wearing years) (Bullimore et al, 2013); and the risk of MK in pediatric OK is equivalent to the risk in a reusable, daily wear soft lens (Stapleton et al, 2008). The risk of severe MK—causing loss of two lines of best-corrected acuity—appears to be highest in overnight soft contact lens wear, not in OK (Stapleton et al, 2008; Bullimore et al, 2013). There’s no doubt that rigid lenses carry the lowest infection risk, which is why they are used in their daily wear modality as the referent in these relative risk studies (Stapleton et al, 2008). Daily disposable soft lenses are the safest of the soft lens cohort (2 per 10,000 patient-wearing years risk of MK); but, if we’re selecting between OK and a reusable soft contact lens option for myopia control, the truth is that the safety profile is similar.

When it comes to myopia control, many major scientific developments have been accidental in origin. The whys and wherefores of OK’s success in slowing myopia progression are too vast a subject to cover here, but two recently published meta-analysis papers confirm that OK is effective in slowing progression of myopia by around 50% compared to controls (Si et al, 2015; Sun et al, 2015). Yes, questions remain on mechanisms and longevity of effect, possible rebound effect, and which patients are most likely to benefit, but the same questions remain for soft lens options. It’s also not as simple as developing soft lenses to mimic OK lens optics, as both changes in spherical aberration and peripheral refraction aren’t directly comparable across OK and soft lens designs of the same refractive power (Ticak and Walline, 2013).

At the very end of his article, Prof. Efron concluded, and I completely agree, that “Contact lens practitioners need to be alert to exaggerated and unsubstantiated claims….” But I’ll go one step further to add the additional warning that even refereed scientific literature can be interpreted differently according to the filter that an individual chooses to apply. This is an important lesson to us all, for we are all human, and as such, whether intentional or otherwise, are subject to the human fallibility of confirmation bias (seeking facts to support our personal viewpoint and avoiding those that don’t) (Watson, 1960). Call me biased too, as my research and work has centered around OK design; but, when we line the facts up side by side, OK has a lot to offer to our patients and to the profession and, for that reason, is definitely worth the bother.

Paul Gifford, PhD, Brisbane, Australia

Look Beyond the Literature I would like to comment on Dr. Nathan Efron’s article in the June 2018 issue of Contact Lens Spectrum. I believe that it contains several inaccurate statements about orthokeratology and myopia control that may reflect the author’s lack of experience with, or knowledge of, the current state of ortho-k and myopia control.

Practitioners read journals to gain information and knowledge so that they can become better practitioners. We need to trust that the writers present up-to-date, accurate, and thorough information. Many well-done clinical studies are available in the literature showing the efficacy and safety of ortho-k (e.g., many are available at www.myopiaprevention.org ). Also, there are several online ortho-k discussion groups in which practitioners present cases and ask and answer questions to improve their understanding and skills. These discussion groups often discuss cases in which upwards of –12.00D of myopia and 5.00D of astigmatism are routinely corrected successfully! The modality has advanced well beyond a maximum power reduction of –2.00D.

Those of us who specialize in ortho-k and myopia control have seen with our own eyes over and over again what a huge difference we can make for the children whom we treat. Casting doubt on this amazing treatment is a tragedy for any kids whose practitioners trusted Dr. Efron’s words and recommended against ortho-k.

Jeffrey G. Jeruss, OD, Marietta, GA

Dr. Efron’s Response:

I am pleased to have this opportunity to respond to the comments of Drs. Gifford and Jeruss. First and foremost, I make no apologies for viewing orthokeratology, as Dr. Gifford puts it, “…through the filter of relying only on published peer-reviewed articles….” Dr. Gifford seeks to equate peer-reviewed publications with non-refereed anecdotal reports, the latter often being prone to distortion through inappropriate experimental design and inadvertent experimenter bias.

There is a historical reason why rigorous, large-scale scientific studies of orthokeratology likely will no longer be conducted; this relates back to the Berkeley Orthokeratology Study (Brand et al, 1983; Polse et al, March 1983; Polse et al, April 1983), funded by the National Institutes of Health to the tune of around $1 million. This single-center, randomized, concurrently controlled, masked clinical trial demonstrated that although orthokeratology was safe, it was largely inefficacious. In response, orthokeratology enthusiasts claimed that the study was out of date as soon as it was published, offering unsupported claims that new designs had recently been devised that would deliver far better results.

I believe that this is the trick of the orthokeratologists. Non-refereed, anecdotal reports demonstrating fantastic results are hailed as ground-breaking, whereas refereed scientific papers questioning the technique are dismissed as out of date and irrelevant because they used last years’ designs rather than this years’ fabulous new designs. Now, of course things have moved on since the 1980s, with changes such as the introduction of overnight orthokeratology and reverse geometry designs; however, the orthokeratologists’ trick is still invoked even when minor tweaks in design are introduced (such as new materials, small changes in diameter, etc.)

Indeed, Dr. Gifford seeks to play the same trick in his discussion of the paper by Charm and Cho. Although the target correction in that study was –4.00D, subjects ended up with corrections ranging from –2.75D to –6.25D—and he wonders “Whether this is enough to brandish OK as being unreliable….” (When I do a refraction on my –4.00D patients, I like them walking out the door with a correction of –4.00D ± 0.00D and 20/15 vision.) But then Dr. Gifford attempts to obfuscate that finding by going on to claim that Charm and Cho’s imprecise orthokeratology refractive results are now out of date, because newer designs will undoubtedly have better reliability.

Dr. Jeruss makes reference to online groups in which orthokeratology enthusiasts “…often discuss cases in which upwards of –12.00D of myopia and 5.00D of astigmatism are routinely corrected successfully.” Such extraordinary claims are simply not supported by the refereed literature, and if anything, they set the field back by establishing unrealistic expectations, misleading colleagues, and disadvantaging patients. Online forums have no place in the scientific discourse.

I was disturbed that Dr. Gifford made the claim that prescribing orthokeratology allows practitioners to retain control of patients rather than being exposed, when fitting soft lenses, to patients sourcing lenses from the internet. This is akin to saying that you are prescribing orthokeratology in the pecuniary interests of yourself rather than the ocular welfare of your patients.

Notwithstanding any of the above, the proof is in the pudding. If orthokeratology is a wonderful clinical modality suitable for correcting all levels of myopia, then all practitioners would be rushing to employ this approach. But, the opposite is true. Over the past 16 years, orthokeratology has represented a meager 0.3% of all contact lenses fitted (Morgan et al, 2018).

Having said all of this, I do recognize the role that orthokeratology research has had in advancing our understanding of corneal mechanics, rheology, and stability; introducing interesting concepts of reverse-geometry lens designs; and pointing the way toward optical designs that can at least partially arrest the advancement of myopia. Indeed, Dr. Gifford himself has many accomplishments in this field, having published important refereed papers on orthokeratology as well as an authoritative textbook chapter on the subject. I applaud his efforts in this regard. However, I feel that Drs. Gifford and Jeruss, and their fellow orthokeratology enthusiasts, are misguided. We will have to agree to disagree as to the true efficacy and popularity of this clinical approach. CLS

For references, please visit www.clspectrum.com/references and click on document #273.