I-site May 2010

International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision

May 2010

In This Issue

Column

Presbyopia

Myopia Progression

BCLA

I(n)site-the-practice

(R)GP art

Agenda

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Column

Makes sense(-itivity)

In the discussion of soft versus (R)GP, it always comes down to comfort in the end - corneal health is better with (R)GPs, vision is better and compliance and lens care are far less of an issue with (R)GPs compared to soft lenses. What is surprising, though, is that so little is actually known about sensitivity of the cornea. Information on how modern lens types affect ocular surface sensitivity is hard to find. Eric Papas addresses the comfort issue in a column in the March issue of Contact Len Spectrum. Pure mechano-receptors, which are what is usually measured, make up only about 15 to 20 percent of the total number of sensory elements on the ocular surface, he states. About four-times more abundant are a group that can respond to the multiple stimuli of heat, chemical irritants of various kinds, and mechanical force. Also in Contact Lens Spectrum, Ed Bennett takes a closer look at the comfort issue with (R)GPs, stating that 'established (R)GP lens practitioners do not have a problem with comfort.' The main question may be - how much comfortare we ready to sacrifice? (R)GPs may be the durable alternative to soft lenses - with better long-term effects - but it is painful to see that we know so little about the comfort issue.

Eef van der Worp

Bi- and Multifocal Lenses

(R)GPresbyopia

If there is any area in particular in which (R)GPs can be beneficial, then it must be for presbyopia. No other vision correction method can be a better alternative for glasses than (R)GPs. But practitioners are not always keen on using them, maybe because the initial success rate is not what they expected. In the 10th annual presbyopia report in Review of Optometry, Christine Sindt summarizes a few tips for success, including a list of patients you may want to avoid in the beginning as they may be more challenging. These include patients who have: against-the-rule astigmatism over 0.75D, with-the-rule astigmatism over 2.50D, oblique astigmatism over 1.00D, residual astigmatism over 1.00D, steep corneas over 48.00D (under 7.00mm) or flat corneas under 39.50D (over 8.50mm), corneal warpage (let the cornea first return to baseline), previous refractive surgery, lid surgery or blepheroplasty, high plus powers, amblyopia, pseudophakia and patients who are long-term monovision wearers. Craig Norman, in a recap of the Global Specialty Lens Symposium, summaries the usefulness of corneal topography in fitting multifocal (R)GP lenses. Apart from being crucial in defining and designing the first lens, it can help determine off-axis optical centres and even aid in pupil size measurement, lid position/shape and dry eye detection.

Myopia Progression

Any progress?

Myopia progression keeps intriguing us, although not everybody in the field is convinced that there is such an effect and these practitioners remind us that it may be too soon to jump to conclusions yet. Let's take a closer look at myopia development itself - what do we know? In an interesting article in Die Kontaktlinse(full article access - German language), Arne Ohlendorf and Frank Schaeffel look at peripheral refraction as a potential factor in myopia development, but they also state that near-activity, long thought to be a predominant factor in myopia development, may not be as important as outdoor activity and light stimulance. In a fantastic review in a 'Borish Awardee' special in Optometry and Vision Science (abstract only for non-members), Donald Mutti underscores the latter conclusion, but also looks at the importance of lens thinning (and the cessation of that at the onset of myopia) and the role of the ciliary body. Melissa Baily further discusses the role of the ciliary body in a very insightful article in Review of Optometry (full article) and makes it clear that the ciliary body in myopic patients (also in children) is thicker than in emmetropic eyes, and she discusses the potential significance of that. A well known association exists between accommodative lag and myopia, and it is speculated that the ciliary muscle plays a prime role in this. But is it cause or effect? Still many questions need to be answered, but progress is being made.

BCLA

Keratoconus & much more

Illustrating that (R)GPs are very much alive, at the upcoming BCLA conference in Birmingham, UK, one of the biggest and certainly most important contact lens meetings worldwide, many (R)GP topics will be highlighted. Keratoconus is one of the main themes throughout the conference, both on the general program and scientific session program. But also myopia, contact lenses & kids and myopia progression are prominent on the program, while topics like orthokeratology and general (R)GP related topics will also be covered.

I(n)-site-the-practice

Designing a Toric (R)GP Contact Lens

The management of astigmatism with gas permeable contact lenses in any practice can be intimidating with respect to complexity of fit and time. This leads to the question, is the prescribing of toric gas permeable contact lenses an art or science? Beth Kinoshita, assistant professor and chief of contact lens services at Pacific University College of Optometry (USA), reviews in this month's I(n)-site-the-practice what makes an ideal lens-to-cornea fitting relationship. There are three fit factors that need to be achieved. The ideal fluorescein pattern that achieves all three fit factors: 1) vaults the central cornea 2) lands at 3 and 9 o'clock and 3) has unobstructed vertical movement. Managing high astigmatism in any practice takes practice, but by mixing technology and a step-by-step fitting approach, the art becomes a science.

(R)GP-ART

Mars

International Agenda

Upcoming Meetings 2010

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: i-site@netherlens.com.