International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision
 April 2013
In This Issue
Column
(R)GP Fitting Survey
Orthokeratology
Hydrops
Scleral Lenses
I(n)-site-the-practice
Agenda
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Column
SpecialEYEze

This newsletter - established June 2009 - provides 'the best of' the literature regarding (R)GP lenses and everything related to them. Lately, the topic of scleral lenses has gained a tremendous amount of attention - because it is new, because it is 'sexy.' But we shouldn't forget that there are many other options available to correct the irregular cornea. First and foremost: good old corneal (R)GP lenses also can provide excellent vision, with the best tear film exchange that any lens will ever give us. Hybrid lenses are getting better with their silicone hydrogel skirts, also providing good vision with good comfort for a number of patients. And custom soft lenses, also widely available in silicone hydrogel materials now, are gaining popularity - primarily because of the last reason (comfort). As noted before - it is all about the quality of life - the balance between comfort, wearing time, vision & safety. Therefore, I like the conclusion stated in the next item: 'It is likely that (R)GP lenses will remain a viable, albeit increasingly specialized, form of vision correction.'  

Eef van der Worp

Rigid Gas Permeable Lens Fitting
International Survey Data - A 5-year Review
 

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Data were obtained for 12,230 (R)GP lens fits in up to 40 countries between 2007 and 2011. Overall (R)GP lenses represented 10.8% of all contact lens fits, but with a wide range: from 0.2% in Lithuania to 37% in Malaysia. Compared with soft lens fits, (R)GP lens fits are characterized by older patient age (37.3 versus 29.8 years), fewer spherical and toric fits; more bi-/multifocal fits, less frequent replacement (75% versus 85% for soft) and less part-time wear (4% versus 10% in soft lens wear). High-Dk (36%) and mid-Dk (42%) materials were predominantly used. Orthokeratology represents 11.5% of (R)GP lens fits according to this survey. It is likely that (R)GP lenses will remain a viable, albeit increasingly specialized, form of vision correction, the authors conclude.

Efron et al - Optometry & Vision Science, Feb 2013
Corneal Reshaping
Orthokeratology & Corneal Astigmatism
 

Two articles in the February issue of Contact Lens Spectrum cover orthokeratology for corneal astigmatism. John Mark Jackson from Memphis (TN, USA) in 'Practice Pearls' reports on a 49-year-old monovision (R)GP lens wearer with a prescription of OD -5.25 -1.50 x 180 and OS -4.00 -1.75 x 30 who wanted to try corneal reshaping. The patient's elevation map showed a difference of 35 microns between the two principle meridians, caused by the corneal astigmatism. A 50-micron difference in return zone depth of the corneal reshaping lens was chosen accordingly. Unaided visual acuity for far and near was 20/20 or 1.0 OU. Typically, it is advocated that if the corneal astigmatism is greater than the spherical component of the refraction, toric orthokeratology lenses should not be considered. However, Antonio Calossi from Florence (Italy) reports on a case in which he was successful in correcting one of his patients satisfactorily despite the OD +1.00 -2.00 x 180 and OS +1.25 -2.25 x 180 base refraction of the patient. As we speak, the Vision by Design meeting of the Orthokeratology Academy of America is taking place in Chicago (USA). Highlights will be covered in an upcoming edition of I-site newsletter.  

Photo: Jaime Paune (Barcelona, Spain)
Hydrops
A Risk (-factor) in Keratoconus
 
The Auckland Keratoconus Study tried to identify predicting factors for acute corneal hydrops in keratoconus. One-hundred-and-one eyes of 101 subjects (mean age 24.6 � 8.4 years) were identified with keratoconus-related corneal hydrops. The researchers concluded that Pacific ethnicity, history of eye-rubbing, poor VA at first hospital presentation and lack of family history were statistically associated with developing acute corneal hydrops in keratoconus in a New Zealand population. In the April Contact Lens & Anterior Eye, a rare case of bilateral acute corneal hydrops in keratoconus is described in a 12-year-old Leber congenital amaurosis patient. Photo: Lynette Johns - Boston MA USA).
Scleral Lenses
Multilingual
 

The scleral lens fitting guide, composed by an international board of scleral lens experts - has been available for download (free) from the Pacific University website for a while. It is now available in a number of translations as well including French, German, Italian, Spanish and the latest addition: Serbian. In addition, a scleral lens case report series (English only) is available from the Pacific website for download, too. 

I(n)-site-the-practice   
Aphakic Scleral Contact Lens
 

Contact lenses are the best refractive option for patients who have aphakia. In particular, (R)GP lenses offer patients superior optics. Corneal (R)GP aphakic lenses can be challenging to fit secondary to increased lens mass that can cause inferior lens decentration. In this case of a patient with a +15.75D lens prescription, not only did the lens decenter, it also exhibited unacceptable lens binding. A scleral lens has the advantage of improving centration and avoiding the consequences of an ill-fitting corneal (R)GP lens. Using a hyper-Dk material is recommended to maximize oxygen transmissibility for aphakic lenses that have increased center thicknesses. Also, UV-protection of the lens material is key, as the natural filtering capacity of the crystalline lens is no longer present. 

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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].