SoftSpecialEdition is a quarterly newsletter that provides independent updates from the international literature on soft specialty lens-related topics. View as Webpage
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Soft Lens Fitting: from Research to Practice
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The two factors that together almost single-handedly define the lens-to-ocular surface relationship are the base curve and the diameter of a contact lens; combined, they are directly linked to the sagittal depth (SAG). Two questions that cross our minds when fitting soft lenses are: 1) How can we optimize our chairtime and effectively select soft contact lens options? And 2) How do we efficiently determine whether patients require a custom soft contact lens to best fit their ocular surface? An example of expediting the fitting process is presented in a case report of a 23-year-old who has struggled with soft contact lens comfort and reports that his eyes are irritated after a few hours of lens wear. His current lens exhibits a shallow fit on eye with inadequate limbal coverage and superior-temporal decentration. To improve the contact lens fit, this patient requires a deeper lens with a higher SAG. For that, the Pacific team has developed SAG-charts, showing the various SAG values of lenses.
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To observe a change in soft lens fit, we predict that SAG adjustments of approximately 250 microns are desired. Ultimately, for this patient, the deepest spherical daily disposable lens available at the time was fitted, which showed adequate centration, lens movement, and approximately 1mm of limbal coverage. The patient reported that this lens was the most comfortable spherical daily disposable ever trialed. But ideally, higher SAGs were desired. Low-cylinder prescriptions can sometimes offer an advantage in fitting individuals similar to our patient, as the stock toric lens counterparts often have a larger lens diameter and therefore a higher SAG value. The SAG charts can help guide clinicians in selecting the next best lens option to trial on eye. But another aspect is that if the deepest SAG lens does not offer an appropriate fit, this can help practitioners confirm that a custom soft lens is the next best option in the fitting process. As we continue to study the various lens designs, we hope to utilize the SAG depth chart in decreasing the rate of soft contact lens dropout. For more, see link below.
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Global Specialty Lens Symposium
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Antiviral Effect of Solutions Against Coronavirus
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The purpose of this study was to evaluate the antiviral potential of five multipurpose disinfecting solutions against coronavirus. Test solutions were Biotrue and Renu Advanced (Bausch+Lomb), Acuvue RevitaLens (Johnson & Johnson Vision), Cleadew (Ophtecs Corp.) and AOSept Plus (Alcon); these were mixed with the virus, and the surviving virus particles from each sample were then quantified. The three multipurpose disinfecting solutions (MPS) did not kill the coronavirus at the manufacturers’ recommended disinfection time in the standalone test. AOSept Plus (hydrogen peroxide) and Cleadew (povidone iodine) did significantly reduce the number of coronaviruses to below the detection limit. This study shows that oxidative contact lens disinfecting solutions (i.e., those containing povidone-iodine or hydrogen peroxide) provide superior antiviral activity against a coronavirus surrogate of SARS-CoV-2, unless the full regimen test (rub, rinse, disinfect) is used in the MPS category.
Photo by Fusion Medical Animation on Unsplash
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Reviewing Contact Lens Solution Preservatives
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Preservatives are essential for preventing contact lens-related microbial keratitis. The purpose of this review was to summarize the current knowledge related to the use of common ophthalmic preservatives in lens care products with respect to both safety and efficacy. The review indicated that first-generation preservatives are no longer used in multipurpose solutions (MPS) due to their high levels of ocular toxicity. Modern, high-molecular-weight preservatives, including polyquaternium-1 (PQ-1) and biguanides (PHMB), are generally effective against bacteria, minimally effective against fungi, and are not effective against Acanthamoeba. PQ-1 and PHMB are likely safe when used with contact lenses, but they may cause ocular adverse events, with roughly equal risk between the two preservatives. Some MPS products contain both PQ-1 and PHMB, but no increased risk of adverse events has been reported when combining the two. Hydrogen-peroxide (H2O2) solutions are effective against all common ocular microbes, including Acanthamoeba, and they have been proven safe with proper compliance. Povidone-iodine (P-I) solutions are not currently commercially available in North America, but they have been shown in other countries to be safe and effective. In conclusion, the authors state that patients should be monitored when using PQ-1- or PHMB-containing solutions, because these preservatives have been associated with ocular adverse events. If events are detected, patients should be switched to an alternative solution. H2O2 or P-I solutions are preferred for any patients who may expose their lenses to water because they are the only solution categories effective against Acanthamoeba. Photo by matt-briney on Unsplash
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Custom Soft Lenses as Alternatives to Sclerals
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Scleral GP lenses absolutely have great benefits; however, there are some factors that limit their use in certain cases. For example, sclerals’ ability to be tinted/painted is limited. And the addition of layers of pigments contributes to overall lens thickness and can potentially impact oxygenation to the cornea. In some of these cases, a custom soft lens that is made 2mm-to-3mm larger than the size of the cornea with an opaque iris ring is an appropriate fitting option, Stephanie Ramdass writes in 'custom soft lens corner' in Contact Lens Spectrum. Furthermore, even a best-fit scleral lens will leave some indentation on the eye. If you remove lenses from established scleral lens wearers during follow-up visits and stain the eye with sodium fluorescein, this indentation ring can be visualized. Stain uptake over a filtering bleb or scleral sutures following trauma is evidence of injury to the underlying ocular surface epithelial cells. If adequate vault over these structures cannot be achieved or an edge/haptic vault is required that leads to a bubble when the patients blink, a custom soft lens can be lathe-cut and fitted to better protect the delicate conjunctiva to prevent erosion. And sclerals can induce hypoxic changes in compromised corneal tissue, even at a minimal lens center and fluid reservoir thickness, she states - especially in eyes that have undergone one or more corneal transplant surgeries. A custom soft lens can sometimes serve as a healthier barrier between the undersurface of the eyelids and the delicate corneal tissue.
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A BCLA global consensus paper delivers guidance to the profession on all aspects of prescribing and fitting contact lenses to allow for best patient care. The Contact Lens Evidicenced-based Academic Reports (CLEAR) were published in the April issue of Contact Lens and Anterior Eye and consist of 11 papers ranging from anatomy and physiology to all types of lenses, including various aspects of soft lens fitting.
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Medical Use of Soft Contact Lenses
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The CLEAR 'Medical use of contact lenses' section hosted by Deborah Jacobs notes that there are several applications of soft lenses in this category. Large diameter soft contact lenses are available for off-the-shelf use in eyes with larger corneal diameters and can be used for medical purposes such as bleb leakage or when there is poor retention of typical diameter lenses due to exposure, ocular surface disease or unusual corneal or scleral topography. Current literature suggests good long-term tolerance of custom soft contact lenses, such as torics; a study that enrolled 105 patients who had astigmatism and who were empirically fitted with a custom toric soft lens found that 74% of the enrolled subjects were able to wear the contact lens full-time and that 89% were able to achieve vision within one line of their best-corrected visual acuity. A more recent 12-month prospective study with a custom soft lens specifically designed for keratoconus in a group of 43 patients found that, at 12 months, 84% of the subjects were still wearing these lenses, with the majority achieving good vision and comfort. Bandage soft lens use is described in detail in this (open access) paper and shows the wide range of indications such as after a range of refractive surgery procedures as well as post-corneal collagen crosslinking; in persistent epithelial defects, corneal abrasions and recurrent corneal erosions; and post-operative use for comfort and healing (such as in penetrating keratoplasty, Intracorneal ring segments, ptosis/pterygium surgery, bleb leaks, perforations and trauma). See link below for the full report.
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Specialty Soft Lens Education
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Specialty Soft Lenses In Your Practice
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'Custom Soft Lens Update for Healthy and Irregular Cornea Patients' is presented in the September 2021 GPLI webinar by Renee Reeder. She describes in this one-hour webinar the importance of looking at soft specialty lens options. See the full webinar below or click this link GPLI.info.
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In the September issue of the GPLI newsletter, the theme 'building your practice with GP and custom soft contact lenses’ was further explored by highlighting the very timely topic of “Myopia Management” in the education spotlight by Jeff Walline. With several soft multifocals currently being used for this purpose and an ever-increasing introduction of orthokeratology lens designs, the myopia control arena is growing rapidly. The presentation reviews clinical studies that showed just how effective every treatment is and followed that up with how you should utilize these treatments in clinical practice as well as how to effectively communicate these options to your patients.
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