International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision
 June 2014
In This Issue
Column
Bifocal (R)GP lenses
Scleral Lenses
Pinguecula
Corneal Thickness
I(n)-site-the-practice
Agenda
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Column
Presby-hope

Recently I was involved in an interesting forum discussion on drop-out in contact lens wear, where I heard a good remark: why patients drop out may be different for different lens modalities. More specifically: while dryness may be a serious reason for dropout for a large cohort of patients, in presbyopic patients it may very well be that 'vision' is the primary reason that drives patients to other vision correction options. I have always said: presbyopes are really a different species. Now that I myself am becoming presbyopic - I can surely tell from my own experience that 0.25D more (or less) in one eye can have a huge impact on my vision and performance! I think it is fair to say that 'it's all about the vision' for presbyopic correction, as Craig Norman puts it in a recent column in Contact Lens Spectrum. Despite good efforts and hopefully better options entering the market - good presbyopic corrections for large groups of patients with soft lenses and with laser refractive surgery are hard to find. And I know that it may seem like a stretch at first - but boy do (R)GP lenses offer a good alternative! Not only do they actually provide a choice in lens system (simultaneous lens designs versus alternating lens designs), the quality of the optics provided is also superb compared to laser refractive surgery and soft lenses. Recently, the GPLI in the USA has hosted a number of (R)GP Multifocal lens webinars that are now available online and are worth checking out. Eye care practitioners like Ed Bennett, Doug Benoit and recently Brooke Messer (May 20, 2014) share their views in these webinars and show how they have had tremendous success with (R)GP bifocals (even with bifocals for the irregular cornea). That is inspiring: there is hope for the presbyope!  

Eef van der Worp 

Presbyopia
Simultaneous (R)GP Lenses: not lost in translation!
 

 

To follow up on the column above, for the advanced lens specialists it may be of interest to know that simultaneous lens designs actually do benefit to some degree from alternation - although not to the full extent that translating lenses do, of course. This is one of the benefits that (R)GP simultaneous lenses have over soft simultaneous lenses. The movement of the (R)GP simultaneous lens on the eye, and the superior decentration of the lens in downgaze, can surely help with getting more of the peripheral 'plus' into the pupil zone upon reading. In a study by Chad Rosen, Josh Lotoczky and Trevor Fosso at Michigan College of Optometry's Vision Research Institute, the optical properties of six proprietary multifocal (R)GP lens designs were analyzed. Although all lenses were ordered in similar parameters, there were significant differences among lens types in distance zone sizes, power graduation from distance to near zone, positioning of distance optics, and optical clarity. The distance zone sizes varied from 2.53mm to 3.78mm among the test designs in this study. What this means is that different designs have to translate more than others do to achieve full add power; or that a higher add may be needed to achieve the desired near add for some lens designs.

Scleral Lenses
Peak Performance
 

The international literature continues to report success stories of scleral lens performance. A snapshot of publications in just the last few months is reported here. According to an article in Eye & Contact Lens (March 2014 edition), failure of rigid gas-permeable lens fitting or intolerance was the common indication for fitting a certain type of scleral lens in corneas with irregular astigmatism. Other reasons for which the scleral lens described was indicated included: pain, photophobia, comfort, ghosting of images, and frequent loss of smaller lenses. In the open access Journal of Optometry, an article and case report refers to the 'Therapeutic use of mini-scleral lenses in a patient with Graves' ophthalmopathy' and an article in the American Journal of Ophthalmology (May 2014) reports on 'Scleral Lens Therapy for Patients With Ocular Symptoms of Chronic Stevens-Johnson Syndrome.' Optometry & Vision Science (April 2014) features two articles on the topic: 'Unique hard scleral lens post-LASIK ectasia fitting' and 'An Ocular Surface Prosthesis for Keratoglobus and Terrien's Marginal Degeneration.' Photo: Lynette Johns 

Pinguecula
Scleral Lens Fitting - turned up a notch
 

Dealing with pinguecula in fitting scleral lenses may be one of the more challenging fitting obstacles, as pinguecula are quite common. Proposed ways of managing this are numerous. Some try to stay away from the pinguecula by downsizing lens diameter, others claim that 'suppression' by large diameter scleral lenses can work. Quadrant-specific lenses for this purpose have been suggested (alleviating pressure in the region of the pinguecula). Another alternative is to 'notch' the lens, thus bypassing the elevated conjunctival tissue. Edward Boshnick in Contact Lenses Today recently presented this option (5th item of the newsletter), as did Brooke Messer in Review of Optometry. In the past, I-site newsletter case reports have addressed this issue as well (Emily Kachinsky). Photo: Emily Kachinsky 
Corneal Thickness
Does Corneal Thickness Differ in Myopia?
 

Is there a relationship between central or peripheral corneal thickness in different degrees of myopia? A (full access) paper in the Journal of Optometry reviews this question.

Corneal thickness is an important indicator of corneal health. Its alteration may be indicative of different pathologies, so in clinical practice it is of great importance to obtain the most reliable corneal pachymetry value for each patient. Corneal thickness is also implicated in the measurement of intraocular pressure or when planning corneal refractive surgery. The outcome of the study reveals there are no significant differences among low, moderate and extremely myopic eyes related to the central and peripheral corneal thickness. Corneal thickness is very similar in myopic eyes with small differences that are not clinically relevant to myopic patient management, the paper concluded.

I(n)-site-the-practice   
Corneal (R)GP lenses after LASIK - do they work?
  

Refractive surgery leaves many myopic patients with an oblate shaped cornea. This oddly shaped cornea can be difficult to fit, especially when using corneal gas permeable (R)GP lens designs. The pre-surgical keratometry values and prior refraction information can be quite useful when attempting to fit these types of corneas. Any information about the ablation zone (diameter of treatment zone) can be helpful as well. If you do not have any of this information, a diagnostic fitting often yields great results. A 57-year-old white female presented to our office. She was a new patient with history of myopia and LASIK performed OD. Her BCVA was 20/40 OD. A reverse curve diagnostic fitting set was used to refit the patient. She achieved 20/25 visual acuity and is pleased with the vision. The patient has been wearing the lens successfully for over 3 months.

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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].