|Quarterly newsletter on Soft Specialty Contact Lens |
Research, Developments, Designs and Materials WINTER 2013
|WORLD WIDE VISION
Kerasoft IC - Your Flexible Friend
Jennifer McMahon is Optometry Lead at The Great Western Hospital, Swindon in the United Kingdom. She presents two case reports illustrating that specially designed custom-made soft lenses can be a versatile lens option that can be successfully applied in fitting mild, moderate and even advanced irregular corneas. They can be a very useful tool especially when a lens is required in one eye only (case 1) or if the patient is having difficulties with RGP lenses (case 2). The Kerasoft IC (Irregular Cornea) lens, used in these case reports, is a soft lens specifically designed for the correction of the irregular cornea including keratoconus and post graft. It is available with both a standard and a sector management control periphery, where individual sectors can be flattened or steepened in relation to their neighbors. Click here for full report.
Treatment Plan for Keratoconus
RGP Lenses, Soft Lenses and Surgical Options
Further on this topic, William Miller of the University of Houston (US) in Contact Lens Spectrum gives his opinion on contact lens and surgical treatment options for keratoconus. 'Customized soft lenses' from different companies are proposed, both for the management of keratoconus in its active state and/or post-surgically after corneal transplant. Photo Jan Pauwels University Hospital Antwerp.
Millar - Contact Lens Spectrum November 2012
|IN THE LITERATURE|
Can we Use OCT to Evaluate
Soft Lens Fits?
Slit Lamp, OCT, Morphology, Cornea, Conjunctiva, Limbus, Soft Lens Fit
The tools for assessing soft lens fits are, unfortunately, limited apart from a subjective 'feel' by the eye care practitioner about movement and dynamics of the soft lens fit. Quantifying it was, up to now, virtually impossible. That may change. 'Using Optical Coherence Tomography to Assess Corneoscleral Morphology After Soft Contact Lens Wear' is the title of a potentially groundbreaking paper by David Alonso-Caneiro, Alyra Shaw and Michael Collins in the November 2012 issue of Optometry & Vision Science. Although the clinical significance of these changes is yet to be determined, it was found that soft contact lenses can produce small but statistically significant changes in the morphology of the limbal/scleral region of the eye and that OCT technology is useful in assessing these changes.
Alonso-Caneiro, Shaw, Collins - Optometry & Vision Science, November 2012
|IN THE LITERATURE|
'What to do with 3.00D of Astigmatism'?
Standard & Toric RGP lenses, Soft Toric Options
Ronald Watanabe in Contact Lens Spectrum says that he is sometimes asked what is the best contact lens for someone with 3.00D of astigmatism. 'It depends,' according to Watanabe - which always evokes a groan, the author explains. But in the article, a good overview is given of the options available to the practitioner. He also states that these days, custom soft lenses in additional multipacks have reduced the pricing to make them affordable after the initial lens fit.
Watanabe - Contact Lens Spectrum November 2012
|IN THE LITERATURE|
Ocular Sagittal Height
and Soft Contact Lens Fit
Sagittal Heigt, Keratometry, Shape Factor, Lens Fit
A paper by Graeme Young on soft lens fitting, from 1992 is a classic and deserves a second look. In the paper, it is made clear that central keratometry readings are not the most useful variable to predict soft lens fit. The shape factor of the cornea, for instance, is a very important factor in predicting the sagittal height of a lens to best fit the eye. And corneal diameter is another very strong variable to consider when fitting soft lenses. Small changes in lens diameter can lead to a huge increase or decrease in sagittal height, while changes in base curve radius have limited effect. In a later paper, Young et all (see below for full access link to the article) looked at the "Influence of Soft Contact Lens Design on Clinical Performance". Up to now, imaging and measuring the corneal-scleral profile and the sagittal height of the ocular surface was impossible, but that has changed with new topographical technology that can measure areas beyond the cornea.
Young, Holden, Cooke - Optometry & Vision Science, 5/1993
|IN THE LITERATURE
Lens Modulus, Mechanical Properties, Silicone Hydrogel
The mechanical properties of a contact lens - also in soft lens wear - are important for visual performance of the lens and for on-eye comfort, Horst et al state in a paper in Optometry & Vision Science. 'The material must be sufficiently compliant so that the lens can conform to the surface of the eye to feel comfortable to the wearer and reduce the risk of mechanical complications such as superior limbal arcuate lesions, contact lens papillary conjunctivitis, mucin balls, conjunctival flaps, and changes in corneal curvature' the paper continues. Assessing the efficacy of current and proposed contact lens materials and designs is important, especially if such designs make use of variable properties to enhance function or fit, according to the paper.
Soft Lens Fit Evaluation
Matt Lampa & Mark André
Successful custom soft contact lens prescribing is rooted and grounded in the practitioner's ability to appropriately assess the fit of the lens. But traditional evaluation techniques are limited. This is where the keratometer comes in. Performing over-keratometry allows us to appreciate what the patient is experiencing through the lens because the quality of the reflected mires is a mirrored representation of the image quality the patient receives. The more regular and consistent the mires appear, the better the potential for correcting the patient's refractive error. Click here for the full report on over-keratometry in soft lens fit evaluation.
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