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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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Scleral Lenses Rock
Considering the attention they get on the international podia and in the media, scleral lenses rock - although their biggest advantage is that they actually don't rock; on the cornea that is! Ed Bennett and Christopher Gilmartin describe scleral lens application and removal in Contact Lens Spectrum, while I-site newsletter columnist Greg DeNaeyer in Optometric Management writes on scleral lens fitting in an article called 'Scleral Fits Simplified.' Also in Contact Lens Specrum, James Li discusses 'Fitting Scleral Lenses in Keratoconus Patients' - a look at different lens designs, fitting techniques and troubleshooting tips. Regarding the latter: in another article in Contact Lens Spectrum, Greg DeNaeyer also covers strategies for decreasing the impact of scleral lens debris, which he explains is one of the most common complications of scleral lens wear. For more on these topics: the scleral lens society hosted a complications and troubleshooting webinar, which can be played back entirely (Java function should be enabled on your computer), in which Melissa Barnett, Mindy Toabe and Lynette Johns cover many scleral lens management and complication questions. See the Sclerallens.org website for more information on scleral lenses.
Eef van der Worp
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Look-alike
Even if you ask corneal specialists how to diagnose pellucid marginal degeneration (PMD), the answer is usually not clear cut. What is clear is that it is a corneal ectasia, but where a decentered oval keratoconus stops and an PMD begins is not always obvious. Another 'look-alike' is keratoglobus, and peripheral conditions like Mooren's ulcer and Terrien's marginal degeration are also sometimes confused with PMD according to a comprehensive review paper on PMD by researchers at the University of Manchester in Contact Lens & Anterior Eye. PMD is a rare ectatic disorder that typically affects the inferior peripheral cornea in crescentic fashion, the paper states. The condition is most commonly found in males and usually appears between the 2nd and 5th decade of life, affecting all ethnicities. The prevalence and aetiology remain unknown. The paper also cannot provide the practitioner with many more practical tools than those commonly known for a more definite differential diagnosis from, for instance, keratoconus, but this eight-page paper must be the most complete reference currently available for practitioners on the topic.
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What's on tap?
Not many case reports in the literature on corneal infections are about (R)GP lens wear. Recently however, a group in Spain reported on a case of a 59-year-old (R)GP lens wearer with an Acanthamoeba infection in Contact Lens & Anterior Eye. The article reports that the patient admitted to have worn the same lenses and used the same lens case for the last 10 years. She also reported moistening her lenses in her mouth and using tap water to wash the lenses. This case report seems to emphasize that although the infection rate in (R)GP lenses is extremely low, we should not neglect to emphasize hygiene and lens care in this modality too. Avoiding tap water in the care regimen of soft lenses and also in orthokeratology seems standard practice now. Maybe it is time to start doing the same for standard (R)GP lens wear. Not only is tap water not biomimetic with the tear film, it also can contain micro-organisms. In addition, regular check-ups should also be emphasized in (R)GP lens wear.
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Economics of Eye Conditions | |
Priceless
Normally we don't think of eye conditions in terms of economic factors. But a recent paper in the American Journal of Ophthalmology by Rebenitsch et al did exactly that: it looked at the lifetime costs of keratoconus in an study called 'The Lifetime Economic Burden of Keratoconus.' The lifetime cost of treating keratoconus over myopia was $25.168. The cost of routine care for keratoconus was found not to be the main concern; the primary factor influencing changes in the cost of care for keratoconus was the probability of corneal transplant. Because of the impaired vision-related quality of life and the relatively young onset of disease, the economic burden of the treatment of keratoconus represents a significant public health concern, the paper concludes. Another paper, also in the American Journal of Ophthalmology focuses on the economic appraisal of a scleral lens (the Boston Ocular Surface Prosthesis). Benefits, based on improvements in visual functioning, were converted to quality-adjusted life years, which was then related to economic values. Shepard et al conclude in this study that the device is cost-effective and cost-beneficial in patients with severely compromised visual function attributable to ectasia, irregular astigmatism and ocular surface disease.
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Double or Nothing?
Probably not out of economic concern, but rather because of the relative lack of cornea donors, a paper in Ophthalmology by Heindl et al reports on the use of a single donor cornea for two recipients by combining deep anterior lamellar keratoplasty on keratoconus eyes and Descemet's membrane endothelial keratoplasty on Fuchs' endothelial dystrophy eyes on the same surgery day. Furthermore, because the need for human donor corneas worldwide far exceeds supply, an article in Cornea opens the discussion on Xenotransplantation, which uses corneas from other species, especially pigs, on human eyes.
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A Simplex Solution
A 74-year-old female patient presented with best corrected visual acuity of 20/200 in her left eye. She had a history of corneal transplant and central scarring secondary to a presumed recurrence of Herpes simplex virus (HSV). The patient was fit with a (R)GP quadrant specific large diameter lens (in the 11mm range). Although the final lens fit is still not ideal, the patient is able to wear the lens comfortably for a full day and achieved 20/40 vision. Corneal scars as a result of corneal infections, especially in HSV, for some reason seem to respond very well to (R)GP lenses with oftentimes surprisingly good visual outcome.
I(n)-site-the-practice by Greg DeNaeyer
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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 is a lecturer for a variety of industry partners, but is not related to any specific company. Please contact us at: [email protected]. |
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