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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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(F)rigid
How 'sexy' are (R)GP contact lenses? In the
annual Eurolens research survey, this modality represented about 13% of lens fits worldwide - with notable differences among countries. In my home country the Netherlands, it happens to be 23% (including orthokeratology). With so much attention given to other lens options - hydrogels but also sclerals and hybrids more recently - we should not forget about 'good old' (R)GP lenses. The benefits are clear - absolute superior vision and the proven highest level of safety. The downsides are clear too, but pretty much limited to 'comfort' as the only main variable. With that in mind, it may be good to not forget to 'sell' (R)GPs - that is, to explain clearly the benefits that these lenses can provide to potential lens wearers. Two recent columns, "Five tips for increased success with GP lenses" in Contact Lens Spectrum by Nancy Chan and John Mark Jackson and "Address these three common GP lens concerns to ease the minds of your apprehensive patients" in Review of Optometry by Stephanie Woo, offer great clinical tips in this regard. I personally think that in every contact lens practice, pretty much anywhere around the world, there is 'room' for (R)GP lens fits to range somewhere between the average 13% and the mentioned 23% - where patients can benefit from all of the great advantages that (R)GPs offer, and the needs of the patients who deserve them can be satisfied. It doesn't have to be sexy - as long as we remember that (R)GPs are just a rigid good lens option.
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Twins
Two identical twins, 8 years of age with comparable near activities, were randomly assigned to wear orthokeratology and single vision lenses, and they were monitored for two years for myopia progression. In terms of cycloplegic refraction after completion of the two-year study, the increase in myopia was 11% OD and 48% OS in the orthokeratology wearing child and 87% OD and 67% OS in the single vision lens wearing child. The overall change in axial length was 0.52mm (OD) and 0.70mm (OS) in the orthokeratology wearing child and 0.77mm (OD) and 0.82mm (OS) in the single vision lens wearing child. Orthokeratology is more effective in controlling myopia progression in terms of axial elongation than wearing single vision lenses in this pair of identical twins, it was concluded in this study.
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It's Axial Length Actually
A study from Spain looked at the refractive effect of 1 week of discontinuation of orthokeratology lenses. The study involved 29 subjects aged 6 to 12 years with myopia of −0.75D to −4.00D and astigmatism of ≤1.00D. They showed that the effects of long-term orthokeratology on ocular biometry and refraction are still present after 1 week of discontinuation of lens wear. Refractive change therefore, after discontinuation of long-term orthokeratology, is primarily attributed to the recovery of corneal shape and not to an increase in the axial length, the paper concluded.
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Dirty (on your) Mind
Patrick Caroline and Mark André in a column in Contact Lens Spectrum focus on epithelial erosions in orthokeratology. According to the authors, central epithelial erosions in orthokeratology may occur early in the procedure or months after beginning the modality. The most common form of early onset epithelial disruption occurs within the first days of lens wear, secondary to the minimal apical clearance present with orthokeratology lens designs. During the initial stages of central epithelial compression, the thinned tear film can result in a transient epithelial punctate erosion, which commonly resolves within two to five days. One other key aspect of erosions in orthokeratology is the removal of lens deposits. A common late-onset complication of orthokeratology is deposit formation on the posterior surface of reverse geometry lenses, according to the authors, which can and should be dealt with to prevent erosions.
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A Solution to the Problem
In Review of Cornea & Contact Lenses, Christine Sindt describes how heavy mucin buildup can complicate scleral lens wear. The more distressed the eye, the more mucus it produces in response to irritation and inflammation, she describes. What to do? The buildup of mucin can lead to chronic discomfort and clouded vision that dissuades patients from continuing lens wear. "But by learning and teaching two simple steps, we can make life much happier for our scleral lens patients," Sindt educates: 1) a cotton swab soaked in conditioner to rub surface deposits off of the lens, and 2) a 5-15ml sodium chloride saline vial placed parallel to the ocular surface and aimed at the edge of the lens, to squirt saline under the lens and rinse out any mucin that is present underneath. A case of toxic keratitis was presented in Contact Lenses Today (5th item in the newsletter) by Edgar Davila-Garcia from Puerto Rico - the patient was diagnosed with an ectasia after LASIK and was wearing scleral lenses to restore vision. The patient was filling the bowl of the lens with a multipurpose solution instead of unpreserved saline solution. After retraining the patient on the proper care, insertion and removal of scleral lenses, the patient used only unpreserved saline to fill the bowl of the lens, and the problem resolved.
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Intracorneal ring segments (ICRS) are currently used as a management option for keratoconus with the goal of improved vision. One or two of these segments can be implanted depending on the patient's condition. But many of these patients still require specialty contact lenses postoperatively to achieve functional vision. A 47-year-old male patient with keratoconus reported for specialty contact lens fitting. The patient had ICRS implanted in both of his corneas 5 years prior. He was fit with 16mm scleral lenses. After dispensing, the patient had 20/25 acuity in each eye and was happy with the comfort and stability of the lenses. For these patients, scleral lenses are often what allows them to successfully wear a gas permeable contact lens that provides them with improved vision and comfortable wear in a stable lens. From a practical standpoint, ICRS surgery potentially may have been avoided if this patient had been previously fit with scleral lenses.
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Upcoming Events
- EAOO, May 15-17, Warsaw PL
- Deutsche Contactlinsen Congress, May 25-26, Munich DE
- BCLA, June 6-9, Birmingham UK
- CLAO, June 12-14, Toronto CA
- Scleral Lens Seminar, June 19-20, Hertford UK
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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: i-site@netherlens.com.
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