|Paragon CRT is being used as an option to slow myopia in younger patients.|
A better understanding of myopia has led to more options to slow its progression in children.
Given that the prevalence of myopia has significantly increased in the past 40 years and there are many new lens options available, is it time to reconsider our protocol for fitting children, specifically, into contact lenses?
According to recent studies, axial lengthening is emerging as the primary culprit in this flood of progressing myopia. Research shows peripheral retinal blur plays an important role in increasing ocular axial length. It is theorized that standard contact lenses and spectacles may cause further myopic regression by only correcting central blur, which simultaneously induces peripheral hyperopic defocus. In other words, the eye is stimulated to continue to grow—further increasing myopia. Correcting this disparity has been the focus of researchers.
Currently there are two correction options being investigated and utilized. The first is a dual-focus soft contact lens that is being considered. Its design fully corrects centrally for myopia but under corrects the periphery, creating two diopters of myopic defocus. Research was conducted with children who wore a dual-focus contact lens in one eye and a standard single vision lens in the other. After 10 months of wear, the average dual-focus eye increased in axial length by 0.11mm versus a 0.22mm increase in the eye with the standard lens. Patients showed a corresponding slowing of myopia in the dual-focus eye. This lens is being studied in Australia but is not yet approved for use in U.S.
Orthokeratology, or ortho-k, is also being utilized to slow myopia. Unlike gas permeable lenses, which slow myopia by flattening the cornea, studies have shown ortho-k actually prevents increases in axial length. Myopic eyes fitted with an ortho-k lens shift from a hyperopic peripheral defocus to a myopic peripheral defocus. This may provide a stop signal for axial length growth. Here is a closer look at some of the more popular ortho-k options on the market today.
OK® E-System. Utilizing the Bausch + Lomb Vision Shaping Treatment (VST) system, this reverse geometry lens from Contex, Inc. is made of the Boston® Equalens® II material and has a Dk of 85. The fit set allows for a quick, straightforward fitting process.
Emerald™ Lens. Produced by Euclid Systems, this lens also uses the Bausch + Lomb VST process. It features a reverse geometry design in a Boston Equalens II material as well. Emerald’s lens design can be fit empirically, from only the refraction, keratometry readings, and a HVID measurement. No fit set is needed, therefore reducing cost and chair time.
Paragon CRT®. This lens from Paragon Vision Sciences utilizes Proximity Control Technology™, which delivers a seamless back surface that prevents lens impingement on the peripheral cornea. The unique laser mark on each CRT lens assures proper lens identification. Paragon HDS® 100 lens polymer, featuring HDS® Technology, was developed with information gleaned from three NASA space shuttle missions. Paragon HDS 100 has a Dk of 100.
With a better understanding of myopia’s development and the availability of specialty lens options, we now are more equipped to slow its progression in children.
Jenny Kiernan practices at Eye Consultants of Colorado, Conifer, CO; Scot Morris is its clinical director.
WHERE TO FIND IT:
Contex, Inc. • 818-788-5836 • oklens.com
Euclid Systems Corp. • 800-477-9396 • euclidsys.com
Paragon Vision Sciences • 800-528-8279 • paragoncrt.com/getcertified