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International Newsletter and Forum on Corneal & Scleral Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision
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I-site newsletter is a global newsletter which is purely educational in nature and launched in 2009, that monthly provides independent updates from the international literature on specialty (R)GP lenses and related topics. To unsubscribe at any time, click the link 'SafeUnsubscribe' at the bottom of this newsletter.
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This title represents a saying in English that means "It's easy to know the right thing to do after something has happened, but it's hard to predict the future." The year 2020 is the year of clarity. Looking back on the very successful Global Specialty Lens Symposium (GSLS) 2020 and back, it is fairly clear that in hindsight, the last decade - between 2010 and 2020 - was the decade of scleral lenses in our industry. At various contact lens meetings late in the 'late zeros,' scleral lenses were scarcely mentioned - if at all. Back in 2010, there were hardly any resources on sclerals; and in fact, that is year the scleral lens guide was written, a guide solely devoted to better understanding the basics of scleral lenses written with the help of a board of international experts in the field. Now, in 2020, everything is completely different. Both the pre-conference track and the general program at GSLS 2020 - and surely the breakout sessions by manufacturers - were full of scleral lens topics. A new scleral lens institute had its inaugural meeting - the International Forum on Scleral Lens Research - on Wednesday prior to GSLS 2020. To top it off - the Scleral Lens Education Society an organization with over 4200 members and 200 fellows - held its annual reception. How cool to see an entire room full of 'scleral lens folks' - from residents to experts, educators, researchers and industry people. Only in hindsight is it easy to say it was clear that this would happen.
Eef van der Worp
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'Take Home' Messages on Orthokeratology
One of the 'take home' educational tools that I
literally could take home from GSLS 2020 was a new book by Michael Lipson called 'Contemporary Orthokeratology.' From getting started to advanced fitting challenges and problem-solving, it is intended to be a knowledge base for novices just learning about the process as well as a reference for those experienced in the practice of orthokeratology. The book opens with a section on the history and development of the process of orthokeratology, then covers the foundation of knowledge and skills needed for the practice of orthokeratology. It then moves through the initial evaluation, candidacy and fitting. A lengthy chapter is devoted to extensive examples of corneal topography. This includes text and numerous graphical examples of tips on how to utilize topography for diagnostic evaluation of pre- and post- treatment maps. Discussion of careful follow-up care, lens care and handling as well as a large section on troubleshooting and problem-solving is included. Finally, there is a section on the basics of practice management in the practice of orthokeratology. Also included is a special supplemental feature: a transcript of a discussion the author had with international experts on the topic of managing myopia with orthokeratology. Contemporary Orthokeratology is an open access source for the current knowledge base of all aspects relating to the practice of orthokeratology. For (free) download, see link below.
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Regional Variations in Post-lens Tear Reservoir Thickness
Both at GSLS and at the
International Forum for Scleral Lens Research Meeting held prior to GSLS, updates on scleral lenses were provided and discussed. Now that significant issues with scleral lenses have been 'colored in' over the last decade or so, it is now time to find the smaller (missing) pieces of the puzzle. Steven Vincent, also one of the keynote speakers at GSLS, recently published a paper on regional variations in post-lens tear layer (PLTL) thickness during scleral lens wear, for instance. While we typically talk about 'the reservoir thickness,' in reality it is a little bit more subtle and variable. Conclusions: the PLTL was thickest temporally and thinnest nasally in healthy eyes fitted with rotationally symmetric scleral lenses, most likely because of regional differences in underlying scleral elevation, eyelid forces and lens centration. PLTL asymmetries diminished with lens wear, and stabilization occurred more rapidly in regions with less corneal clearance immediately after lens application. A tilted optic zone was observed immediately after lens application, with the greatest asymmetry between nasal and temporal regions (156±22 μm more clearance temporally) and superior nasal and inferotemporal regions (124±12 μm more clearance inferotemporally). The magnitude of lens settling observed in each region was associated with the initial PLTL. The superior nasal PLTL furthest from the pupil center stabilized after 90 minutes compared with other regions that stabilized after 4 hrs. On average, after 8 hrs of lens wear, the PLTL decreased by 29%, and PLTL asymmetries between opposing regions decreased by 30%.
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Corneal Endothelial Blebs Induced by Scleral Lens Wear
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The purposes of this study from the University of Montreal were to determine whether blebs appear after scleral lens wear and whether their appearance is influenced by lens clearance as well as to compare bleb and cell sizes. In the bleb phenomenon, some endothelial cells transiently lose their specular reflection. This has been reported during contact lens wear and goggle-induced hypoxia or hypercapnia. The investigators found that after 25 minutes of wearing scleral lenses, the lenses with the targeted 400 micron clearances induced significantly more blebs than did the ones with 200 microns of clearance, suggesting evidence of reduced oxygen and/or increased carbon dioxide levels under scleral lenses fitted with excessive clearance. Consequently, to avoid chronic hypoxic stress on all corneal layers and to minimize hypercapnia - in addition to the obvious increase in Dk/t of the lens - scleral lenses should be fitted with limited clearance because this minimizes bleb response. This may be accomplished regardless of the lens diameter, provided that the lens is well supported by all quadrants of the conjunctiva. In that regard, for larger lenses, toric haptics may help achieve an optimal fitting
Image Giasson et al OVS Nov 2019
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Central Corneal Thickness and Intraocular Pressure
In line with the previous item, a statistically significant increase in central corneal thickness after scleral lens wear in subjects with ocular surface disease was found by Shahnazi et al, which may be attributed to subclinical hypoxic conditions created by scleral lens wear. In addition, this paper looked at intraocular pressure (IOP) changes in scleral lens wear, a topic that was discussed in several fora in Las Vegas too. No significant relationship was found between scleral lens wear and IOP, but IOP measurements in this study were obtained at the initial scleral lens consultation and at follow-up visits immediately after lens removal. This could 'break the seal' of scleral lens wear, and hence the real effect of scleral lenses on IOP could be underestimated. Other ways of measuring IOP with the scleral lens in place were proposed at both the scleral lens forum and at the general meeting. It looks like the jury is still out on this topic.
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Upcoming Events
- NCC 2020, 15-16 March, Veldhoven (NL)
- EFCLIN, 23- 25 April, Berlin (DE)
- EAOO, 15-17 May, Helsiki (FI)
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- Orthokeratolgy Society of Oceania, 5-7 June, Gold Coast (AU)
- International Congres of Scleral Contacts, July 24-25, Ft Lauderdale (US)
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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:
[email protected].
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