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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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Reshaping our Vision?
Orthokeratology in its new 'shape' has been with us for quite a while: it's been almost 15 years since its re-introduction. It's funny, back then it was regarded as 'the technique of the future.' And somehow, I feel that's still the case. So when will the future of orthokeratology become reality? Anno 2014, some eye care practitioners embrace orthokeratology ('loving it'), but at the same time the general uptake has been slow, and many ophthalmologists are still not in favor. Yes, complications do occur in both children and adults. The infection rate is somewhere in the range of that for extended wear soft lenses, it seems. The question may be: what is worse, six diopters of myopia (with a higher risk of cataract, glaucoma, retinal detachment and macular degeneration) or a small risk of corneal infection? That may be a tough call in the consulting room. Granted, myopia control can be done with soft dual-focus lenses as well. But what are the infection risks involved with that, when children wear these lenses (swim, shower and nap in them) all day? What seems paramount is: all of the practitioners I've talked to who have a flourishing orthokeratology lens practice are serious about it. They check on compliance and have a good and decent system for follow up - i.e., skipping six-month check-ups is not allowed, and patients will be tracked down and called repeatedly about why they didn't show up for their exam. Tapwater is a no-go, and annual replacement is the norm typically. These practitioners tell me they see very few complications. Orthokeratology is for some patients only. Is it for some eye care practitioners only, too?
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Reviewing Corneal Reshaping
Michael Lipson, a long-term corneal reshaping enthusiast from the University of Michigan (US), writes the 'Overnight Corneal Reshaping in 2014 and Beyond' overview in Contact Lens Spectrum. He mentions the slow uptake by eye care practitioners in the US. Although accurate data is not available, estimates indicate that 6000 to 8000 US practitioners are certified to fit orthokeratology lenses. First, and most important, he states, is staff education and enthusiasm. 'All office staff should be well-versed in discussing orthokeratology with patients, creating excitement about it, and identifying who may be good potential candidates. It's ideal to have staff members become orthokeratology users.' Second, the author states it is helpful to create an informed consent or 'fitting agreement' that spells out the services that will be provided to patients as well as what is expected of them. This includes items such as risks and benefits, necessity for compliance in wearing and care, follow-up schedule, emergency contact procedures, what is included in the initial costs, ongoing costs, replacement lens costs and other office policies. Having the patient involved this way, as a joint decision and responsibility, may be key for a successful corneal reshaping practice.
Lipson - Contact Lens Spectrum, May 2014
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Orthokeratology Myopia Control
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Is Corneal Power Predictive of Myopia Progression?
It doesn't seem to be a question anymore as to whether orthokeratology slows down myopia progression in children - but rather how much it does so, and in whom? Further evidence to the already large base of studies supporting this hypothesis was published in Optometry & Vision Science. A group from China aimed at investigating the relationship between corneal refractive power change along three axes (nasal, temporal and inferior) and 2-year axial growth in children 9-14 years of age. Subjects with a larger magnitude of corneal relative peripheral power along specific axes experienced slower axial elongation. It is hypothesized that this is caused by the greater amount of relative myopic defocus on the peripheral retina. The investigators conclude their paper by saying: 'our study lends weight to potential orthokeratology lens designs for myopia control in children'.
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Lets Get this Strayt
When light reaches the eye, some of it is scattered forward and backward, and the rest forms the image on the retina. Light that is forward scattered projects a veil of light over the retinal image, which reduces the contrast of the image produced and thus diminishes vision quality. This veil of light is called straylight. Previous studies have shown that light scattering by the cornea can change after refractive laser surgery: both straylight reduction and increase has been reported. The current study found in orthokeratology that straylight significantly fell from baseline values in values reported at 1 month, 3 months, 6 months and 12 months of treatment. Interestingly, one month after discontinuing orthokeratology, straylight was still significantly lower than baseline. No correlations were observed between straylight values and high contrast visual acuity. The paper's conclusion was that good refractive outcomes and reductions in straylight were observed in response to corneal refractive therapy for myopia, and that the reduction in straylight observed after discontinuing orthokeratology warrants further investigation.
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Orthokeratology & Swimming - a Risk?
Contact Lens and Anterior Eye reports an unfortunate case of Acanthamoeba infection. A 34-year-old woman, who had been wearing corneal refractive therapy lenses for myopia correction for 3 years, presented with the complaints of tearing, burning, photophobia, and moderate pain of 4 days duration after having bathed in a swimming pool that was poorly maintained. Non-compliant contact lens wearers, use of tap water or exposure to potentially contaminated sources of water are risks for corneal infection. Swimming in lenses is considered a risk factor for infection in contact lens wear, specifically for Acanthamoeba infection. Orthokeratology represents a different situation in which the lenses are not worn during the day and the lenses themselves are not initially exposed to water, as they are worn overnight. However, the current report indicates that patients corrected with orthokeratology should be warned that under certain adverse conditions, a contaminated swimming pool may pose a potential risk of severe adverse events, the paper states.
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A Caucasian male, 52 years of age, had been wearing contact lenses since he was in his 20s. Over the last 7 years, symptoms of presbyopia have been bothering him. He tried several different contact lens options, including monovision, (R)GP translating and simultaneous lens designs as well as hydrogel translating and simultaneous designs, but none of these solved his problems entirely; either discomfort (dry eye) or vision related problems still occurred. Orthokeratology eliminates the dry eye issue, and with the new bifocal design, simultaneous bifocal images are presented to the eye in a manner similar to other (R)GP or hydrogel lens systems on the market.
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I-site is an educational newsletter that is distributed on a monthly basis and provides an update on rigid gas permeable related topics (scientific research, case reports and other publications worldwide). I-site is objective and non-political. Its editor Eef van der Worp, optometrist, PhD, FAAO, FBCLA, FIACLE, FSLS is a lecturer for a variety of industry partners, but is not related to any specific company. Please contact us at: i-site@netherlens.com.
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