The new, darker version of the Corning 450X Glare Cutter lens is just one example of how technology continues to advance in the area of glare control for low vision patients.

Glare is a steady dazzling light, according to the dictionary. But, when it comes to low vision patients, there's a lot more to it than that, says Randy Jose, O.D., a practitioner and educator from Houston. "It's really light that interferes with the retinal image."

The key, he adds, "is to differentiate the increased sensitivity from glare, which originates when light comes into the eye from any direction, versus photophobia's effects from straight-ahead light."

Understanding this basic difference, Jose explains, "affects what you do with filtering out the light." Glare often occurs from the periphery, and Jose explains to his patients that "it is like static from a radio."

There are, in fact, several ways glare can affect a low vision patient. They can be bothered by: The brightness of car headlights at night or sunlight; the flicker from fluorescent lights; the reflectance of differing depths of snow; the gloss of words and images from shiny book pages; and the brightness of words and images on a computer screen.

Thomas Porter, O.D., director of Low Vision Services at the St. Louis University School of Medicine's Department of Ophthalmology, describes additional situations. "These include: Negotiating the dark and light areas of a flight of steps; differentiating the solidity of the cement on a sidewalk from a crack; the ability to tell the contrast of which area of grass was just cut," he says.

"Glare can be worse than blur, even affecting print contrast for reading in some cases," explains Susan Gormezano, O.D., a low vision practitioner near Detroit.

The Common Causes

What causes it? According to Bruce Rosenthal, chief of the Low Vision Programs at New York City's Lighthouse International, "One of the most common causes is media opacities, especially the early stages of cataracts. If a patient has a small cataract, glaucoma, and a small pupil, he will have considerably more glare."

Practitioners do, in fact, cite a long list of causes. They include: Age-related macular degeneration, diabetic retinopathy, retinitis pigmentosa, aniridia, albinism, and multiple sclerosis, as well as pan retinal photocoagulation patients and post-laser surgery patients, who experience problems at night.

Selecting Treatment Options

Rosenthal advocates anti-reflective coatings for indoor and outdoor use with low vision patients who experience glare difficulties, as well as visors and hats for outdoors. To block glare from shiny book pages, he recommends a typoscope. Side shields and specialty glare controlling lenses and glasses need to be assessed in a variety of lighting conditions-from dim illumination to fluorescent lights. A glare control lens primarily enhances contrast and improves functional vision and mobility as it attenuates light transmission. These lenses are available with varying amounts of filtration for infrared and ultra-violet rays.

ne choice is an eyeglass shield that can be used for driving, reading, and mobility both indoors and out. These glasses can be used by patients who don't wear prescription eyewear, and they can also be fit over prescription glasses. They're available in different color lenses and frames, in a variety of sizes, and also as clip-ons or flip-ups.

In terms of lens designs and materials, glare reducing lenses can be created for designs ranging from single vision to progressives in glass and polycarbonate. And, in terms of technology, a photochromic lens controls glare under any lighting condition, whether indoors or outdoors. Among the most recent advances in photochromic technology is a new, darker version of the Corning 450X Glare Cutter lens.

Presenting Lens ChoicesSelecting the appropriate lens is made easier with glare control lens demonstration kits. Gormezano says that she is often "tipped off to a glare problem when I observe patients squinting as light levels change, or when the best corrected acuity degrades as levels are increased." A rheostat control on the overhead lights helps her with this determination. She also notes glare recovery time both with and without filters.

Adds Jose, "I have my patients cup their hands around the eye like a visor or side shields and then try different colors of lenses to select the appropriate lens for controlling glare. While patients say they feel better, I always ask 'Can you still see?'" The reason, he adds, is to keep from selecting a lens that will reduce the light transmission too much.

"I use a Power Point slide program on a computer in my office that I developed to enable patients to see the enhancing effects of a glare control lens," says Porter. "When I have selected the appropriate lens, the image and words will just pop out for the patient." An additional benefit to Porter's program is that the normally sighted person who is accompanying the patient can see an image in the same way the patient with a glare and contrast deficit sees the image. "Counseling and educating both the patient and the care giver are equally important," adds Porter.

Practitioners say success with glare control lenses is based on achieving a balance. "It's about "manipulating the filtering properties of a lens to enhance contrast while cutting glare," explains Porter. Finding this balance between increasing contrast and minimizing glare, say practitioners, can make a huge difference in patients' lives. EB