FOCUS ON LOW VISION
The contrasting problem of glare
By Susan P. Tarrant

Glare is a problem for everyone. But it can be debilitating for anyone with low vision. The most common prescription for glare is sunwear. But unless an eyecare professional is very thorough before prescribing this quick fix, he or she could simply be trading one problem for another.

With most low vision issues-whether they be from macular degeneration, diabetic retinopathy, glaucoma, pre-operative cataracts, or in some cases post-operative cataracts-patients experience two things: an acute sensitivity to glare and the loss of contrast perception. The loss of contrast perception renders the patient unable to distinguish between objects of similar color or shade.

"Gray or green sunlenses are great for the non-low vision patient, but they don't help low vision patients one bit," says Thomas Porter, O.D., assistant professor in the Department of Ophthalmology at St. Louis University School of Medicine. "I constantly stress to practitioners, that they must deal with patients' contrast sensitivity as well as their glare sensitivity."

The most common way of retaining contrast while decreasing glare is through the use of blue attenuating lenses. Several companies manufacture filtering lenses or blue-blocking goggles specifically for the low vision patient (see sidebar). Depending on the product, the lenses can be ground into a prescription, or come as goggles that can be worn alone or fit over existing eyewear. Most are in the yellow to red end of the color spectrum.

"I'll see a patient whose well-meaning eyecare practitioner has put him in sunlenses with gray or green lenses. Often, the patient tells me he has to take them on and off because they are too dark in some situations," Porter says. "I tell them I could reduce the glare just as much by putting a bucket over their head."

Optician Jerry Mansell, owner of MagnifEYErs in Ft. Lauderdale, Fla., agrees. "Low vision patients need as much light as they can get. The problem is, we have to deal with the blue. That's where these shields and filtering lenses come in. Gray blends shadows and objects together. The yellow or amber will bring out edges in objects and makes them a little easier to pick up."

Colors and Safety

There is a caveat to the absorptive filter lenses, however. While bringing out the contrast between objects, they can alter the perception of color. To a patient who is able to function more independently due to the lenses, however, shifting colors may be unimportant.

"I don't have a problem dispensing these lenses to patients after I tell them, 'I can help you with two major problem areas, but you'll have to give up a little bit in a third area,'" Porter says.

Many marginal low vision patients Mansell sees are still able to drive, he says. Those patients are not successful with the filters because they report difficulty in distinguishing between the colors in traffic lights. For them, Mansell dispenses amber or vermilion lenses, which still control glare while letting in more light.

But since the vast majority of low vision patients no longer drive, Porter says he sees a great safety benefit in the lenses. "Patients with limited vision are prone to tripping over cracks in sidewalks or uneven ground," he says. "That's where the contrast issue comes into play. You can enhance the patient's safety immensely by helping with their contrast."

Dispensing Tips

While the concept of increased contrast perception and reduced glare is usually enough to sell a low vision patient on the filters, practitioners need to determine the degree of sensitivity, as that will determine the coloring of the lens dispensed. Manufacturers provide practitioners with color guidelines to ensure the maximum benefit to the patient.

Convincing the patient of the need is usually the easy part. "One of the first questions I ask is, 'Does glare bother you?'" says Porter.

"If they say yes, I ask if it helps to cup their hands around their eyes. If they say yes and they're wearing green or gray lenses, I ask if the lenses are too dark sometimes. At that point, I tell them there is a lens that will help the glare as much as their sunglasses, and will help with their perception of contrast," Porter adds.

	Solar Shield from Dioptics distributed by Eschenbach.

Often, low vision patients have a hard time adjusting outside to inside and they complain that when they go into a supermarket, for example, the fluorescent lights are so harsh they can't see. So Mansell suggests wearing the goggles or filters all day long.

"Patients also tend to keep their shades drawn at home to cut the glare," he explains. "Well, these patients need all the light they can get, so by wearing these lenses they can deal with the glare without having to live like hermits in a cave.

"Both experts say that once patients put on one of the blue attenuating products, they are immediately sold.

Regardless of the degree of visual problems or the solutions dispensed, Mansell and Porter agree that educating the patient about lifestyle changes is the most important hurdle to success.

"Education is a very large part of treating low vision," Mansell says. "Patients have to learn to do things differently, whether it's wearing a filtering lens or goggle, sitting closer to the TV, or reading with a magnifier "