SoftSpecialEdition is a quarterly newsletter FOR HEALTH CARE PROVIDERS that gives independent updates from the international literature on soft specialty lens-related topics. View as Webpage
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Do Specialty Soft Lenses Need Different Care?
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Much attention in the specialty lens field goes to the fitting process and to the indication range, but the success—or failure—of specialty lenses relies in large part on contact lens care. The short answer to the question in the headline: all contact lenses that are reused need to be disinfected between use; this is something that cannot be emphasised enough to patients. This is particularly true for specialty lenses, which are almost by default ‘reused' and include custom soft multifocals, extended-power-range soft lenses, soft lenses for irregular corneas, prosthetic lenses, coloured lenses, etc. In the case of specialty lenses, patients often have a compromised ocular surface (such as dry eye or because of various conditions), which may make this disinfection step even more urgent. The choice of disinfecting solution may depend on how frequently the lenses are worn and the sensitivity of the wearers to excipients such as preservatives and disinfectants contained within the formulations. ECPs should be aware of the difference between multipurpose solutions and multipurpose disinfecting solutions (see full article). The broad-spectrum antimicrobial efficacy of oxidising disinfection systems, such as systems that use hydrogen peroxide or iodine, even have activity against SARS-CoV-2 and, to a large degree, against Acanthamoeba cysts, something that most multipurpose solutions don’t have unless the rub-and-rinse regimen is carefully followed. One other 'biggie' is the lens case: replacement is key, and in our studies we found that using lens cases that are different from the ones that the manufacturer recommends with a disinfecting solution is a risk for greater microbial growth in the case. See link below for the full article by Mark Willcox: first author on the CLEAR paper on contact lens wettability, cleaning, disinfection and interactions with tears.
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Global Specialty Lens Symposium
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Soft Toric Multifocal versus Toric Orthokeratology
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Spherical orthokeratology and soft multifocal contact lenses are commonly used for myopia management. Astigmatism is more prevalent in myopes compared to hyperopes, but there are limited myopia control contact lens options for patients with moderate to high astigmatism. The purpose of this study was to quantify changes in higher-order aberrations (HOAs) in myopic astigmatic eyes fitted with toric orthokeratology and soft toric multifocal lenses, as both have shown to increase spherical aberration, coma and total HOAs. In this study, the researchers found both lens types to show an increase in HOAs compared to baseline, which placed patients outside of the age- and pupil size-matched normative ranges. But toric orthokeratology induced more HOAs, spherical aberration and coma than soft toric multifocals did. What this means is not entirely clear. In theory, an increase in HOAs may be beneficial to the myopia management effect. However, the predominant theory for myopia control remains the induction of peripheral myopic defocus. The induction of HOAs may concurrently have unintended consequences on visual performance.
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Retinal Defocus in Myopes with Dual-focus Lenses
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Hyperopic defocus, even when absent from the central 10°of the retina, accelerates eye growth and, thus, myopia. The term “hyperopic defocus” describes the situation in which the image plane lies posterior to the photoreceptor plane, which can occur if the eye is too short for its optical power. Dual-focus (DF) soft lenses employ regions of added plus power, designed to introduce myopic defocus as a way of controlling the effects of any hyperopic defocus, and have been shown to slow the rate of myopia progression. However, the efficacy of such plus-power-containing treatments often varies from child to child. One possible explanation is that some eyes experience varying amounts of hyperopic defocus, and therefore different degrees of induced myopic defocus, in part due to their accommodative response when fitted with myopia control DF lenses. Evaluation of the accommodative responses of 40 young myopes revealed significant between-participant differences in accommodative accuracy that were maintained across a wide range of viewing distances, most notably at the nearest target distances. DF lenses successfully provided a majority of myopic defocus for the subjects, who had good accommodation at all viewing distances in this study despite increased negative spherical aberration at near. The results indicate that even individuals with higher accommodative lags may still be treated effectively with MiSight 1 day DF zonal lenses containing +2.00D defocus, but they might experience more benefit from an optical design with a higher defocus. Collectively, these results also indicate potential clinical utility in measuring accommodative lag, pupil size and ocular aberrations when implementing myopia control treatment.
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Patients who are dissatisfied with 20/20 visual acuity may have underlying higher-order aberrations. Matt Kaufmann in this Contact Lens Spectrum article takes aberrometry from the research lab and applies it to clinical practice. As clinicians, it is important that we continually strive to better comprehend our patients’ quality of vision, he states. Talking to patients and understanding how they visualize the world rather than judging their quality of vision based on a single visual acuity number is a first step. A wavefront aberrometer is a tool that can be incorporated into a clinical environment to expand upon these details. Wavefront maps have the ability to quantify the way in which light travels through the eye. They can be used to produce graphics and visualizations such as point spread functions and visual acuity letter retinal image simulations that can help clinicians understand their patients’ vision, lead to more accurate diagnoses and produce better treatment outcomes. It is exciting to see wavefront-guided lenses start to emerge in the commercial market, according to Kaufmann.
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Expand Your Fitting Options with Custom Soft
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Robert Davis and Moshe Schwartz look beyond mass-produced lenses to delight patients who thought that they could not wear contact lenses. The mass-produced soft contact lens market has a tool chest filled with similar products that fit alike, with comparable power availability and nearly universal diameters. When this tool chest of lenses is not successful, custom lenses can fill the void. These custom lenses can be fabricated in any power, cylinder, or multifocal configuration including distance-center, near-center, annular or aspheric designs, for myopia management as well as for presbyopia. They can also be manufactured with prism for vertical imbalance, with thicker lens profiles to correct irregular astigmatism or as tinted or opaque colored lenses that can improve cosmesis and contrast sensitivity as well as problems with glare. Patients who have severe light sensitivity will benefit from filtered custom contact lenses for conditions including cataracts, macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa. In short: soft custom lenses offer practitioners the opportunity to recommend lens wear to patients who were previously told that they could not wear contact lenses, thereby enhancing their quality of life. This contact lens modality can enhance patients’ cosmetic appearance and visual abilities in a way not provided by any other lens type, and it offers freedom from glasses and improved contact lens comfort for non-average eyes. Custom soft contact lenses solve the problems inherent in a “one-lens-fits-all” fitting philosophy, the authors state. Photo by Barn Images on Unsplash
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Customizing Presbyopia & Astigmatism
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In Customizing with Confidence, Brooke Messer looks at the role of custom soft contact lenses, specifically in the arena of astigmatism and presbyopia. First, she states that corneas and contact lenses with similar central curvatures can have very different sagittal depths due to overall diameter differences. She urges readers to look at that, but also at pupil size, eyelid characteristics, the ocular surface and the (type of and magnitude) of the refractive error. This way, you can recognize your candidates, and she provides very practical tools in the form of two tables listing all of the characteristcs to do so. Working with custom soft lenses can improve your skills at evaluating all types of contact lenses, Messer states. Much like our irregular cornea patients trying scleral lenses for the first time, custom-designed soft lenses can be just as impactful for our astigmatic and presbyopic patients.
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Myopia: More Benefit Than Risk
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Without intervention, sight-threatening complications from high myopia will become more common. But a question that regularly pops up in clinical practice is: What are the risks? Corneal infiltrative events (CIEs) occur at rates between 300-to-400 per 10,000 patient years in adults; in patients 8-to-12 years of age, this is 97 per 10,000 patient years, and it is 335 per 10,000 patient years for ages 13-to-17 years. But CIEs are not sight-threatening. Sight-threatening microbial keratitis (MK) is less common: in daytime soft lens wear, the incidence is two-to-four cases for every 10,000 patient years in adults. Prescribing a daily disposable lens decreases the risk of corneal complications. The frequency of MK in children 12 years or younger appeaers to be no higher than what is observed in adults. This is important, because it is the typical age group for which myopia management with contact lens therapy is initiated. On the benefit side: the greatest benefit of reducing myopia is a resulting decreased risk of complications that are associated with visual impairment such as retinal detachment, myopic maculopathy, glaucoma and cataracts. Without intervention, sight-threatening complications from high myopia will become more common. The societal burden for these events will be enormous and greatly outweighs the modest and largely manageable risks of pediatric contact lens wear, according to Frogozo.
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Fitting & Acceptance of Photochromic Soft Lenses
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This multi-site prospective study describes the subjective visual performance of wearers and the proportion of neophytes who can successfully be fitted with photochromic soft lenses. Across 11 sites, 105 adult neophytes completed the study following four weeks of wear. Ninety-seven percent of participants were considered to have been successfully fitted; 60% reported better vision outdoors, and 62% reported less squinting compared to with spectacle wear. Neophyte participants expressed positive opinions about the study lenses compared to their current spectacles. Photo by wu yi on Unsplash
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Piggyback Photochromic Lenses for Visual Rehabilitation in Traumatic Aniridia
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Miyoshi et al from Brasil report a case of fitting with a photochromic silicone hydrogel contact lens under a rigid gas-permeable lens (piggyback system) for photophobia and low vision correction after traumatic aniridia and aphakia. The 40-year-old woman was referred to the practice for contact lens fitting in her right eye, which was left aphakic after an open globe injury. She also presented traumatic aniridia in the right eye, and her left eye had been previously eviscerated. A successful fitting was obtained with a photochromic silicone hydrogel (senofilcon A) contact lens with a +13.00D rigid gas-permeable lens on top. The patient displayed visual acuity and contrast sensitivity improvement and reported decreased photophobia.
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