International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision
December 2010
In This Issue
Artificial Cornea
Corneal and Scleral Shape
(R)GP art
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You never get credit for things that don't happen

How many contact lens-related corneal infections did you have in your practice last year? The end of the year is always a good time to look forward, but let's not forget to reflect back and appreciate the things that happened this year. And the things that didn't happen. In politics, it is a given that you never get credit for things that don't happen, but it is the same in our practices. We put a lot of emphasis on lens safety and compliance. And despite the fact that the literature and many colleagues on the podium keep telling us that our patients' compliance is bad, whether through our fault or not, the end result is not all that bad as contact lenses continue to satisfy millions of people around the world without a large number of significant problems. This is especially true with (R)GP lenses as we know. Ed Bennett in the (R)GP annual report in Contact Lens Spectrum (October 2010) highlighted nicely that large-diameter/scleral lens designs, multifocal designs and corneal reshaping seem to have the greatest potential. Personally, I think that in every single practice, anywhere in the world, between 10% and 20% of patients can benefit from (R)GP lenses. Soon we will have the Eurolens survey data on lens fits available again for a reality check. But for now, I am going to pour a nice (big) glass of red wine, look back and think of all the red eyes that we didn't see in our practices this year. Wishing you a happy (and white) Christmas and a bright and safe 2011.

Eef van der Worp

Solutions Used in Scleral Lens Wear
Survey Results

Thanks to all of you who participated in the online Scleral Lens Solution Survey. Respondents came from 4 continents, 50% from Europe, 34% from North America, the rest from Asia and Australia - 46 in total. Thirty-seven percent of respondents reported to have worked with scleral lenses between 1-3 years: 45% 4 years or longer. Half of the respondents reported fitting up to 12 scleral lens fits per year (18% for 7-12 per year). Thirty percent do more than 25 scleral lens fits yearly.

  • Keratoconus was the number one indication to fit scleral lenses (91%), followed by corneal grafts (82%) and pellucid marginal degeneration (76%), then a number other corneal irregularities followed. Thirteen percent reported using scleral lenses for presbyopia.
  • For lens size there was a nice bell-shaped response: 55% of respondents indicated fitting mainly 14.6-18mm lenses, roughly 36% are mainly fitting larger or smaller diameter scleral lenses than that and 20% of respondents reported fitting 'all of the above' lens sizes.
  • GP lens solutions were the number one solution used for lens storage (72%) followed by peroxide systems (48%) and soft lens solutions (17%) (respondents were asked to 'check all that apply').
  • For scleral lens insertion (also subject to 'all that apply'), non-preserved saline was by far the most popular response (72%), followed by (R)GP lens solutions (22%), soft lens solutions (7%) and preserved saline (7%). A relatively large group indicated 'other' (28%), possibly referring to tear supplements.
Artificial Cornea

Something to track in the new year is the development of an artificial cornea. The results of a study by Fagerholm et al on biosynthetic corneas to restore vision in 10 patients (nine keratoconic eyes and one with a mid-stromal scar) was presented. At the two-year follow up, all 10 biosynthetic implants remained not only stable, but the researchers also found that cells and nerves from the patients' own corneas had grown into the implant. In six of these patients vision improved, and with contact lenses vision was comparable to conventional corneal transplantation with human donor tissue. See the October issue of Review of Ophthalmology for coverage of the study and the link below for an abstract of the original paper.

Light Noise

Straylight, which is described as 'light noise,' has gained a lot of interest lately in contact lens wear, not only during this Christmas time. A team from Amsterdam (the Netherlands) looked at straylight in soft and (R)GP lens wearers, and they found that the amount of straylight in soft lens wear was similar while wearing soft lenses and after their removal. In (R)GP lens wear the straylight measurements were much larger in general: during lens wear for certain, but even after lens removal. This effect was mentioned as potentially due to deposits on the lens as well as from unwanted corneal topography changes underneath of the lens.

Corneal and Scleral Shape
A (good) relationship?

The relationship between the corneal shape and the (anterior) scleral shape is poorly understood. Does corneal toricity extend into the periphery and out into the sclera, for instance? From clinical experience it may appear that this is the case in congenital astigmatism, but we don't know for certain. Muriel Schornack and Sanjay Patel published a study in Eye & Contact Lens in which they looked at whether steep and flat keratometric values and reference sphere data from corneal topography correlated with the base curve radius of scleral lenses. They found that this relationship was present, but the link was weak. Based on this, they suggested that diagnostic fitting may be the most appropriate method for fitting scleral lenses at present. Earlier, another study reported in Contact Lens Spectrum seemed to find that typically the nasal anterior sclera is flatter than the rest, which is in line with the typical flatter corneal curvatures found with topography. More data on this will be presented at the Global Specialty Lens Symposium in Las Vegas (see agenda).

 Merry Christmas

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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: