Overnight Contacts

Myopia January 29, 2006 When we view an object, light comes into the cornea (the transparent covering over the eye). The image is bent by the cornea and lands on the retina (the light sensitive membrane at the back of the eye). Specialized cells in the retina translate the information and send it through the optic nerve to the brain for processing. People with myopia (nearsightedness) can see near objects more clearly than distant objects. This occurs because the shape of the eyeball is elongated, or the cornea has too much curvature. Light entering the eye is focused in front of the retina rather than directly on the retina, causing the image to appear blurred. According to the American Optometric Association, myopia affects about 30 percent of Americans. Signs of the condition usually first appear in school age children. Treating Myopia Vision problems, like myopia, can be treated with corrective eyewear (glasses or contact lenses). The American Academy of Ophthalmology estimates 148 million Americans (more than half the U.S. population) wear some type of corrective eyewear; about 34 million wear contact lenses. Myopia can also be treated with surgical procedures, called refractive surgery. In laser-assisted in situ keratomileusis (LASIK), doctors cut a small flap into the top of the cornea and remove some of the underlying corneal issue. The process flattens the top of the cornea and allows light to focus onto the retina. In photorefractive keratectomy (PRK), a laser is used to selectively remove some of the top layer of the cornea, flattening the surface. Correcting Myopia with Contacts Some eye care professionals are using another technique for correcting myopia, called corneal refractive therapy (CRT). CRT aims to reshape the cornea through use of special rigid contact lenses. In 2002, the FDA approved the first CRT system for overnight use, called the Paragon CRT®. Paragon CRT uses gas permeable lenses. When placed in the eye, the lenses apply a slight pressure to the center of the cornea. That pressure redistributes the cells in the outer layer of the cornea - pushing those in the center toward the outer edges. With fewer central cells, the cornea flattens, allowing light to be redirected more appropriately onto the retina. Patients using the Paragon CRT lenses are custom-fitted by a special computer program. The lenses are placed in the eyes at night and removed in the morning. Unlike traditional gas permeable lenses, the CRT lenses are larger and more permeable (100 percent permeable vs. about 30 percent for traditional lenses). Patients may initially feel some discomfort from the slight pressure, but soon become acclimated to the nighttime lenses. In the morning, when the lenses are removed, the cornea has been flattened and vision is improved. Corrective lenses are generally not needed during the day. However, the effect of the nighttime reshaping is only temporary. Gradually, the cornea returns to its natural shape and vision will become blurred. Research shows about 60 percent of people using the Paragon CRT lenses experienced 20/20 vision or better. More than 90 percent reported visual acuity of 20/32 or better. In some cases, the therapy can even improve some cases of astigmatism. It takes about 10 days of therapy to reach best maximum visual acuity. If patients arent happy with the results, the treatment can be discontinued. The cornea will return to its natural state in about 72 hours. There are some risks associated with overnight contacts, like corneal swelling, infection, inflammation, or ulceration. However, studies so far have not seen any significant problems. CRT is not recommended for people who have eye inflammation or infection, eye disease or injury, dry eyes or allergies to materials or solutions used in the production and care of overnight contact lenses. Cost of Paragon CRT is about $1,500, which includes fitting and 2 pair of lenses (a second pair is recommended so therapy is not disrupted in case one set is broken or lost). Doctors recommend the lenses be replaced yearly. In the future, researchers hope to develop a similar system for patients who are farsighted or need bifocals. Paragon CRT is just one corneal reshaping system on the market. Bausch & Lomb also markets lenses called Vision Shaping Treatment™ (VST). Vision reshaping therapy may not be covered by insurance. AUDIENCE INQUIRY For information on Paragon CRT® - http://www.paragoncrt.com For information on the Bausch & Lomb Vision Shaping Treatment™ - http://www.bausch.com For information on myopia: American Academy of Ophthalmology, public website, http://www.medem.com American Optometric Association, http://www.aoa.org BIBLIOGRAPHY Becherer, P.D., and J.A. Kempf, "Endothelial Response to Overnight Corneal Reshaping," Eye & Contact Lens, October 2004, Vol. 30, No. 4, pp. 207-210. Berntsen, D., et al., "The Effect of Overnight Contact Lens Corneal Reshaping on High-order Aberrations and Best-Corrected Visual Acuity," Optometry and Visual Science, June 2005, Vol. 82, No. 6, pp. 490-497. Caroline, P., and J. Choo, "Modern Corneal Reshaping With Contact Lenses," Ophthalmology Clinics of North America, September 2003, Vol. 16, No. 3, pp. 405-413. "Correcting Your Vision with Glasses and Contacts," San Francisco: American Academy of Ophthalmology, downloaded from public website (http://www.medem.com), January 11, 2006. Gardiner, Helen, O.D., et al., "Quantifying Regression with Orthokeratology," Contact Lens Spectrum, October 2005, downloaded from website (http://www.clspectrum.com), November 11, 2005. 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"Refractive Errors and Refractive Surgery," Francisco: American Academy of Ophthalmology, downloaded from public website (http://www.medem.com), January 11, 2006. Tseng, C., et al., "Overnight Orthokeratology-associated Microbial Keratitis," Cornea, October 2005, Vol. 24, No. 7, pp. 778-782. Walline, J., et al., "The Childrens Overnight Orthokeratology Investigation (CCOKI) Pilot Study," Optometry and Vision Science, June 2004, Vol. 81, No. 6, pp. 407-413. Young, A., et al., "Orthokeratology Lens-Related Corneal Ulcers in Children," Ophthalmology, March 2004, Vol. 111, No. 3, pp. 590-595. Research compiled and edited by Barbara J. Fister