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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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Sp(l)ineless
 I have been debating with myself for a while now about what topic to choose for this column from the recent Global Specialty Lens Symposium in Las Vegas (USA). What an awesome meeting we had, with participants from over 30 countries! OK then - let's not be spineless, let's be brave. I think the major thing I got out of the meeting this year is the need to move forward and improve and upgrade our industry with the newest technology. This reminds me of an interesting recent column in Contact Lens Spectrum by Clarke Newman. It is under, of all things, the 'Business of Contact Lenses' section of the journal. But he touches on a very important point: 'splines'. In simple terms, splines try to mathematically describe a complex shape-like the corneal shape. We don't have to understand plines. We just need to use it. Splines, based on corneal topography, can make better custom-made (R)GP lenses: these lenses are superior both in comfort and in supporting corneal physiology (and corneal integrity). Corneal topography has been widely available for more than ten years now, but I don't think we are using it to its fullest potential yet. See also this month's case report in this I-site Newsletter for a nice example from Switzerland of what advanced (R)GP lens fitting can do for us. And the good thing is - we don't have to wait for the future for this to happen. It is here! Eef van der Worp
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Vision by Design
 It is not a coincidence that the growth in popularity of orthokeratology and that of corneal topography happened around the same time: indeed, ten years ago at the introduction or the rebirth of orthokeratolgy in 2001 (see link for an article in Global Contact on that topic). And orthokeratology keeps intriguing us. A paper by Querios et al in Eye & Contact Lens in November 2011 looks at anterior and posterior corneal elevation after orthokeratology in comparison to after standard and customized LASIK. The topograpic changes that take place on the front corneal surface after orthokeratology and LASIK might seem similar when looking at the curvature maps, but the quantitative analysis with a Pentacam (Oculus Inc) showed remarkable differences in this study. Changes in the elevation of the front corneal surface are 2 to 3 times greater after LASIK than in orthokeratology, they found. No posterior changes were found in any procedure. An article in Contact Lens Spectrum looks at corneal cross-linking and orthokeratology. To learn more about orthokeratology, the best thing to do almost certainly is to go to the Orthokeratology Academy of America's fascinating meeting under the title 'Vision by Design'. The program is online now, with a very interesting line-up of speakers. |
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Linking CXL to LASIK
Corneal crosslinking (CXL) has been linked mostly to keratoconus up to now. The recent 'Pioneers Day' in London hosted by Nigel Burnett Hodd and the British Contact Lens Association (BCLA) provoked an interesting discussion between the audience and the speakers-all corneal surgeons-on whom to refer for the procedure. The proposition 'if it were my child with keratoconus - I would certainly refer for a CXL procedure' was backed up by the entire panel. But more and more, CXL is now also linked to LASIK. Refractive Eyecare journal ran an editorial on this topic by David Muller. Muller believes that crosslinking has the potential to play a major role in LASIK and to eventually become a noninvasive refractive procedure entirely on its own. See the link below for the full editorial (free access, after registration).
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Topography-Based (R)GP Lens Fitting
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Relevance of Eyelid and Tear Film Attributes
Genís Cardona and Roser Isern looked at the influence of eyelid and tear film factors in correctly predicting (R)GP lens fitting. They found that lid position, and to a lesser extent tear meniscus height, are determinant factors in explaining the differences between computer-simulated lens predictions and in situ fittings in negative spherical (R)GP lenses of low to moderate power in normal corneas. The study did not use custom-made, topography-based lenses, but rather relied on fitting a standard tricurve (R)GP lens using the topography-based system and the in situ manual fitting based on trial set fitting. The authors conclude that in view of the present findings, a large scale, multicenter study including a variety of lens powers (including torics) and designs (including aspheric) may be required to verify the outcome, but that these factors can further assist in developing the next generation of topography-based contact lens fitting.
Eye & Contact Lens, November 2011 |
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Flexing the Quads in Keratoconus
 In cases with irregular corneas due to ectasia, fitting (R)GP lenses can be challenging. The contact lens needs to fulfill the visual demands of the patient as well as provide the least physiological impact to the weak cornea. In this case, the current (R)GP lens of the patient, a 9.30mm diameter aspheric, rotationally symmetric design, demonstrated apical touch and inferior lift-off. This made the contact lens extremely uncomfortable and additionally induced some diffuse corneal scarring. To achieve better comfort and centration, we fitted the ectasia with a quadrant specific lens with a larger overall diameter to allow the lens to click into the peripheral corneal curvatures. Quadrant specific lens designs consist of a spherical optic zone and free, definable peripheral curvatures in all four quadrants, providing outstanding centration and crisp clear vision. Click here for the full report of this quadrant specific lens fit from Michael Baertschi, Michael Wyss and Simon Bolli from Switzerland.
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Upcoming Events
- San Diego Specialty Lens Symposium, Febr 24-26, San Diego USA
- NCC 2012, March 10-12, Veldhoven NL
- Asia Orthok and Specialty Lens Conference, March 30-31, Hang Zhou (China)
- Vision by Design, April 19-22, Scottsdale USA
- BCLA meeting, May 24-27, Birmingham UK
- Orthokeratology Society of Oceania, July 6-8, Gold Coast AU
- ISCLS congress 2012, September 7-12, Kent UK
- ECLSO congress, September 14-16, Nice FR
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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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