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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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Top of the Eyesberg
When I look back five years at the July 2009 I-site newsletter, which happened to the second edition ever - not a single word is mentioned on scleral lenses. Today, that is quite rare: pretty much each issue has at least some scleral lens coverage. This edition even features a 'special' on the topic, simply because there is that much material available. In fact, there is more material available today than the newsletter can host: the publications mentioned here are really just the top of the iceberg! To start off: a review paper has become available, published in Contact Lens & Anterior Eye (see next item in this newsletter). It is of interest to see the 'peak' in scleral lens publications in the late '60s, early '70s - but more recently (in the last 5 years) an even larger peak can be seen. These are just the peer-reviewed journals. More from the academic fields; see the item with coverage from ARVO 2014 with a special eye on scleral lenses and some interesting findings - ranging from endothelial cell changes to wavefront correction with sclerals. To illustrate the 'growing-up' of scleral lenses: we now worry about residual over-refractions in scleral lenses, which is hosted in an article in Contact Lens Spectrum that is covered here. To top things off: an interesting case report by Lynette Johns on scleral lens diameter: which one is better, large or small? In ocular surface disease, large diameter lenses can not only increase comfort, but also may reduce conjunctival staining. Top-hats off, to sclerals!
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Reviewing a Revival
The scleral lens review paper mentioned above, based on a literature search by researchers from the University of Minho in Portugal, states that most of the reports in the peer-review literature agree that scleral lenses are a good option for diseased corneas and ocular surfaces, although some limitations still exist. Their fitting is mostly based on a steep learning curve, and the practitioner's experience plays a great role in success. It was concluded that the indication range of scleral lenses in contact lens practices seems to be expanding, and it now increasingly includes less severe and even non-compromised eyes too. The occurrence of adverse reactions in uncompromised eyes wearing scleral lenses has not been commonly reported in the peer-review literature. Adverse events with these lenses are rare, but the clinician needs to be aware of them to avoid further damage in eyes that often are already compromised. For the domain of fitting the non-diseased eye, the balance between risk and benefit is less evident at this point than in diseased eyes.
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ARVO 2014 - Orlando
Orlando (US) hosted the Association for Research in Vision and Ophthalmology ( ARVO) meeting earlier this year. Scleral lenses were on the menu. Corneal edema is a potential consequence of scleral lenses, and Kornberg et al (poster#2039) looked at the potential changes this could have to the endothelial layer. The mean endothelial cell density at fitting was 2453 cells/mm2 and this decreased slightly over the mean 113 days of scleral lens wear to 2417 cells/mm2, but the change as not statistically significant. The change in heterogeneity of cell size (polymegathism) and the percentage of hexagonal endothelial cells (pleomorphism) also didn't reach statistical significance. Sui et al (poster#2670) looked at wavefront correction with scleral lenses. Misalignment of a full magnitude wavefront guided scleral lens correction can result in image quality worse than no correction. The purpose of this study was to model optical performance of an 18.2mm diameter scleral lens with toric peripheral curves to assess whether it provides adequate registration precision to implement a full magnitude 2nd to 5th radial order wavefront guided correction without inducing significant change in visual acuity (< 1 line). They found this to be true for all five keratoconic eyes modeled. Agranat et al (poster#1464) looked at the impact of five years of scleral lens wear (using the Prosthetic Replacement of the Ocular Surface Ecosystem, PROSE). Mean age of patients at lens fit was 58 years, but with interesting range from 8 to 96 year. Two thirds of candidates with complex corneal disease was still wearing the devices after five years. Patients with corneal ectasia/irregular astigmatism have a higher rate of continued wear at five years than patients with ocular surface disease. Theophanoous et al (poster#5542) found that PROSE devices can both reduce ocular symptoms and improve visual acuity in patients with Chronic Graft versus Host Disease. Even patients who did not report better visual acuity benefited from improved ocular comfort.
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Advanced Scleral Lens Fitting
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Scleral Lens Residual Astigmatism
 To illustrate the evolution, and the growing-up of the scleral lens modality: Contact Lens Spectrum hosts an article on 'Managing Scleral Lens Residual Astigmatism'. If the sphero-cylindrical over-refraction has less than 1.00D of cylindrical power, the authors advice to prescribe the equivalent diopter sphere or a scleral lens with aspheric optics. Although the residual cylinder does not decrease with an aspheric design, the spherical aberration may be reduced, leading to improved vision the authors state. If there is more than 1.00D cylindrical over-refraction, then over-keratometry or topography can help differentiate between internal astigmatism and lens flexure. Astigmatic 'over-Ks' indicate the presence of lens flexure; spherical 'over-Ks' indicate that the over-refraction cylinder is due to internal astigmatism. The latter can be resolved with a front-surface toric scleral lens. To prevent unwanted lens flexure, the advice is to increase the lens center thickness 0.1mm for each diopter of flexure. Peripheral toric system can be incorporated as well to decrease lens flexure on eye, improve scleral alignment and enhance lens comfort. Photo: Henny Otten, Visser Contactlenzen
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Guia Para Adaptação de Lentes Esclerais
The latest edition of the A Guide to Scleral Lens Fitting, based on the input of a well renowned international educational board, is the Portuguese version. All language editions are available for download, courtesy of Bausch & Lomb Boston, from the Pacific University website. Apart from English and Portuguese, language editions include German, French, Spanish, Italian, Serbian and Japanese. Two versions of Chinese (traditional & simplified Chinese) will be published in the fall. In the process of being translated currently are Korean and Russian. The Scleral Lens Case Report Series, with 30 cases on scleral lens indications, fitting- and management tips also can be downloaded from the Pacific University website (English only), courtesy of Microlens of the Netherlands.
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Covering Scleral Lens Coverage
There are many advantages of both small and large diameter scleral lenses. Selecting the diameter for the patient can be a challenging decision. For instance, if the scleral topography shows asymmetry, then selecting a small diameter may be more advantageous. Otherwise using a larger scleral lens on an eye with scleral asymmetry may require toric or quadrant specific back surface curves in the lens designs for proper alignment. Some patients who have ocular surface disease request their lenses to be made larger because they are symptomatic beyond the edge of the lens. Their most common symptom is feeling dryness and topical lubricants are not always sufficient. In this case, there also a reduction in conjunctival staining underneath the scleral lens was seen. Should this therapeutic effect also be a consideration to use a larger diameter? How large do you make the lens? There is still a lot we need to learn about scleral lenses and parameter selection.
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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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