Prescription, glare-reducing filters give improved visual function
FULLERTON, Calif. Patients with greater glare sensitivity whose needs cannot be met with ordinary sunglasses are finding relief with some specialty lens products.
"Generally, these patients require a prescription," said Douglas R. Williams, OD, an associate professor of optometry at Southern California College of Optometry here.
Corning Medical Optics, NoIR Medical Technologies and Transitions Optical have recently introduced new glare-control products. "These lenses allow us to meet some particular needs of the patient that can't be met with standard ophthalmic lenses," Dr. Williams noted.
Developed by request
For years, glare-reducing lenses have been proven to benefit many people with light sensitive conditions, said David J. Kerko, product development manager for Corning Medical Optics, a pioneer in blue light filtering technology and maker of prescription and plano GlareControl photo chromic glass lenses. The Glare Cutter, introduced last year, was specifically developed by request for the low vision practitioner.
"GlareCutter is only available in single vision, progressives and multifocals," he said. The GlareCutter was developed for patients with beginning sensitivity to bright sunlight and glare outdoors. Transmittance is 18% in a lightened state and 6% in a darkened state. The lens blocks 100% of potentially harmful UV rays and is recommended for patients with developing cataracts, macular degeneration and diabetic retinopathy. The color resembles mahogany.
"When a patient requests from his or her doctor a lens that will help with light sensitivity while complaining about dark, fixed-tint glasses, the practitioner now has a new glare-controlled lens that is not only cosmetically appealing, but very functional as well," Mr. Kerko, co-inventor of the lens, said. The lenses are also chemically tempered to meet Food and Drug Administration impact-resistance requirements.
Corning also offers standard photochromic lenses such as PhotoGray Extra and PhotoGray Thin & Dark, which have been successfully used by some low vision patients.
"Basically, these lenses attenuate the blue end of the light spectrum. This is generally the area with which low vision patients have difficulty," said Tina R. MacDonald, OD, a low vision rehabilitative optometrist in Santa Monica, Calif. "Many people have problems with glare, but they don't realize it because they've never been tested."
Dr. Williams noted, however, that any patient complaint about altered color perception "may be overshadowed by the reduction in glare that he or she experiences with the filter."
Fitting the lenses is subjective, with Corning offering transmittance rates from 67% (light yellow) down to 9% (dark). "Someone who has retinitis pigmentosa will choose a darker lens," Dr. MacDonald said. Many of her patients, however, prefer a light filter for their reading glasses because it improves contrast. "It makes dark things appear darker and white things appear whiter, so print jumps out at them better," she said.
In situations where glass lenses are not appropriate, Dr. MacDonald will match the appropriate color in plastic.
This summer, NoIR Medical Technologies will debut a nonprescription sunglass that offers a full range of color and frequency protection. "It is closer to the face. It's not rectangular and square and full of angles like most of the wraparound glasses," said A.B. Gleichert, resident of the company. In addition, NoIR has three wraparound sizes to be worn over prescription glasses, in more than 50 colors and light transmissions.
"You can prescribe from about 90% all the way down to 2%," said Dr. Williams. Two other advantages of the plastic NoIR filters include affordability and wide side shields, he added. Moreover, frames can accommodate children and adults.
"Future glare reduction products will use measurements, such as optical densities and nanometer ranges, to address specific patient needs," Mr. Gleichert said. "For example, orange filters are useful for macular degeneration patients. The current NoIR model N60 will be defined by optical density 3.5 200-532 nm with a visible light transmission of 49%, which will be helpful for a specific macular degeneration patient."
Bruce P. Rosenthal, OD, chief of low vision programs at the Lighthouse Inc. in New York, also noted that an added benefit of some glare-reducing lenses are their ability to enhance contrast. "Many patients adapt quickly from outdoor to in door lighting," he said.
Ultraviolet light is also absorbed by the lens. Dr. Rosenthal said, "Ultraviolet light seems to be one of the contributing factors in the development of cataracts."
Transitions Optical Inc. in Pinellas Park, Fla. is another photochromic manufacturer, although its plastic lenses are strictly for general use. The company's recent Transitions III prescription lenses have a mid-index of refraction (1.54 to 1.56), plus an 88% transmission of light in an unactivated state and 25% to 30% in an activated state.
"In addition to the comfort, you get UV protection," echoed John C. Crano, associate director of optical products research for PPG Industries Inc., the majority owner of Transitions Optical.
"By reducing the glare and the amount of light and enhancing contrast potentially, these patients are going to be more comfortable and see better," said Dr. Williams. By using a filter that transmits slightly higher in the blue range, "color values are not quite as distorted."
For Your Information:
- Douglas R. Williams, OD, can be reached at (714) 847-6059.
- Tina R. MacDonald, OD, is a clinical adjunct instructor at the Southern California College of Optometry and can be reached at (310) 458-3501; fax: (310) 458-8179.
- Neither Dr. Williams nor Dr. MacDonald has a direct financial interest in the products mentioned in this article nor is either a paid consultant for any companies mentioned.
- Bruce P. Rosenthal, OD, may be reached at (212) 821-9627; fax: (212) 821-9710.
- John C. Crano may be reached at PPG Industries Inc., 440 College Park Dr., Monroeville, PA 15146; (412) 325-5150; fax: (412) 325-5225; e-mail: firstname.lastname@example.org.
- GlareCutter is available from Corning Medical Optics, HP-CB-5-1, Corning, NY 14831; (800) 742-5273; fax: (800) 215-2578.
- David J. Kerko may be reached at Corning Medical Optics.
- N60 is available from NoIR Medical Technologies, Box 159, South Lyon, MI 48178; (800) 521-9746; fax: (313) 769-1708; Web site: http://www.noir-medical.com/. A.B. Gleichert is president of the company.
- Transitions III lenses are available from Transitions Optical, 9251 Belcher Road, Pinellas Park, FL 34666; (813) 545-0400; fax: (813) 546-4732.