|Quarterly newsletter on Soft Specialty Contact Lens |
Research, Developments, Designs and Materials SUMMER 2012
|WORLD WIDE VISION
Soft Contact Lenses-Where do we go now?
I was at a meeting recently where the topic, 'where do we go from here in soft contact lenses' was discussed. This reminded me of a number of observations that I have made over the years of seeing soft lens wearers and it brought up a few points that I think are worth exploring. We now have 40+ years of soft lens wear experience, and I do know that there are corneal changes in patients who have been wearing lenses for many years (although this is not the case in all soft lens wearers). In my view, first of all, there is a need to further understand corneal physiology in soft lens wear. And secondly (and crucially from a clinical standpoint), what is the role of lens fit in optimizing corneal physiology? I wouldn't be surprised if there is a contributing factor and that we should re-evaluate the way we fit soft lenses today. Click here for full report
|IN THE LITERATURE|
Soft Toric Multifocals-A Special Treat
Visual Performance, Astigmatism, Presbyopia
Ron Watanabe in Contact Lens Spectrum emphasizes the need for toric multifocal lenses. We may be missing out on this segment of the presbyopic population, he states. If a patient has more than 0.75D of astigmatism, vision will be compromised with a standard multifocal lens. But soft toric multifocal contact lenses are available, and practitioners should be aware of these. Most have aspheric designs, but there are also concentric designs, combination concentric/aspheric designs, and segmented lenses. In addition to these, the article states, several other custom laboratories manufacture conventional and frequent replacement soft toric multifocal contact lens options with any parameter desired - also in silicone hydrogel materials.
|IN THE LITERATURE|
Lipids on Silicone Hydrogel Materials
Staining Lipids In Vivo on Silicone Hydrogel Materials
Lyndon Jones and colleagues were among the first to report on lipid deposition on silicone hydrogel contact lenses (Eye & Contact Lens) in 2003. Their study found that silicone hydrogel materials bind significantly more lipids and significantly less proteins compared to traditional hydrogel materials. Later studies have shown that the amount of lipids bound may not be all that different in comparison to traditional hydrogel contact lenses. It is obvious that more insight is needed to understand how silicone hydrogel materials interact with the tear components and how these interactions may be associated with reduced performance (e.g., corneal staining, comfort). Andrew Pucker and Jason Nichols in Optometry & Vision Science looked at different stains to detect tear film lipids deposited on silicone hydrogel contact lenses. Both Nile Red and Oil Red O were able to detect lipids on soft lenses in both in vitro and ex vivo conditions on silicone hydrogels. Oil Red O appears to be a better stain for silicone hydrogel lenses as it offers a higher signal to noise ratio.
|IN THE LITERATURE
Albinism & Children
Fitting an Iris Ring Soft Toric Contact Lens
Christine Sindt in Contact Lens Spectrum discusses ocular albinism in young children. First of all, children with albinism often have 3.00D or more of refractive astigmatism, according to the author, and may experience nystagmus. Uncorrected astigmatism can lead to amblopia. Providing the full correction at the earliest possible age in life is important, Sindt advises. Secondly, to address the photophobia that occurs in ocular albinism, very young patients are typically fitted with annulus tint/iris ring (12mm, 20-minute brown tint with 5mm clear pupil) lenses. Older children may be fitted with a solid tint to add a 'sunglasses effect' for the central 5mm. The size of the clear pupil can be adjusted in custom-tinted designs. These lenses can potentially have life-changing effects, as not only the refractive error and the photophobia are treated, but the nystagmus can improve leading to a further increase in vision.
|IN THE LITERATURE|
Custom-Made Soft Lenses
Post-LASIK, Lens Design Supported Software
Pascal Blaser and Stefan Facher, who previously wrote for the Soft Special Newsletter, published a clinical article in th German contact lens journal 'Die Kontaktlinse'. In this article (in German) that is called 'Die Versorgung von irregularen Hornhauten mit weichen
Kontaktlinsen' they report on the important role that soft custom made specialty lenses can play in today's contact lens practice. They report on a sophisticated online software program, that helps them design the custom made soft lenses. Particularly in post-LASIK patients this can be an outcome they state, as RGP lenses may be extremely difficult to fit on these odd shaped corneas.
Die Kontaktlinse, 1-2/1012
|ON THE WEB
Building, Marketing and Managing a Contact Lens Practice
Apart from excellent soft contact lens fitting modules, as referred to in the winter edition of the Soft Special Newsletter, the international association for contact lens educators (IACLE) has now released its practice management modules. Topics include: Building a Successful Contact Lens Practice, Marketing a Contact Lens Practice, Managing a Contact Lens Practice and Standards of Practice. All modules are available for everyone interested (after free registration).
Myopia Control, Higher Order Aberrations
At the association for research in vision and ophthalmology (ARVO) meeting held in Ft Lauderdale (US), many posters were devoted to contact lenses. Peripheral refraction of the eye was one of the main topics, as this may help in reducing the amount of myopia development in children. Brien Holden et al (poster # 6300) presented the 5-year follow-up data of a dual-focus soft lens, showing promising results of 40% reduction in myopia progression in children. This is just with a standard lens - the effect may potentially be larger with custom-made myopia-control lenses, as may be indicated because variation of the effect is very large among individuals. Higher order aberration correction on the front surface of soft lenses is another topic of interest. Ramkumar Sabesan et al (poster # 3661) presented a study in which they showed that higher order aberration correction can even increase the stereopsis in lens wearers. In keratoconus, the higher order aberrations can be six times higher than in the normal eye. Correcting this can obviously improve vision, but keratoconus patients may have to get used to the new correction through a system of neural adaptation, as they have become accustomed to the higher order aberrations present in their keratoconic eyes (Geunyoung Yoon et al, paper # 1718).
Large Diameter Soft Lens after type I Boston Keratoprosthesis
Treatment of Corneal Dellen after Pterygium and Recurrent Erosion
In Eye & Contact Lens, a case by
Anne Keating and Roberto Pineda reports on a therapeutic soft contact lens with a diameter of 16mm and a 8.9mm base curve. Therapeutic contact lenses to prevent desiccation of the ocular surface are commonly used with keratoprostheses. This does, however, put patients at a greater risk of developing a corneal infection. In this case, the patient did develop a fungal infection after the first 3 months postoperatively were unremarkable and uneventful. At the 3-month visit, deposits on the lens were noted, and the lens was cleaned and replaced. The infection was treated successfully, after which another therapeutic lens was placed (photo: courtesy of Peter Nolf, the Netherlands).
Soft Specialty Lens Power Optimization
Matt Lampa & Mark André
In determining the appropriate power for the ammetrope in an initial diagnostic custom soft contact lens, first vertex the manifest refraction to the plane of the cornea. This can be of extreme importance as we are potentially dealing with large refractive errors. In toric soft specialty lens fit, this becomes more complicated and challenging. Matt Lampa and Mark André look this time in their series on Soft Specialty education at soft toric cross-cylinder calculations and calculators. Click here for the full report.
This Newletter is Kindly