There are two things holding back broader use of lens coatings on prescriptions for low vision patients.

One is the misconception that simply because low vision aids and devices can sometimes only make images bigger and  brighter -- instead of crisper and clearer, which is the goal of traditional vision correction -- add-ons like AR don't help. Second, in the absence of any meaningful reimbursement, practitioners often have to think in pragmatic terms rather than in terms of offering optimal solutions to their low vision patients.

These are just two of the factors that have caused the low prescription rate of certain optical coatings to this patient group. But is this the right course of treatment? And more importantly, can these coatings really help low vision patients?

To answer those questions, EB asked a number of low vision specialists which optical coatings were prescribed for their low vision patients and with what frequency. As the chart demonstrates, usage of scratch coats and tints, especially those for glare control, is frequent. Though most of the practitioners we surveyed say AR is probably of value, few report automatically prescribing AR coating for low vision spectacles.

That's particularly ironic, because those same doctors also report that many of the low vision devices they order -- telescopes and magnifiers as opposed to spectacles that they dispense -- do come coated. And, they add, many include multi-layer AR coatings to improve image quality and offer durability.

Here's a look at what several eyecare professionals say about the importance of coatings in products prescribed for their low vision patients.

Anti-Reflective Coatings

"The few prescriptions that come with AR coatings are appreciated by the patient," says Randall T. Jose, O.D., director, Houston Delta Gamma Low Vision Center at the University of Houston College of Optometry, "but often patients do not appreciate the increase in price associated with this add-on."

Does it make sense to AR coat devices like magnifiers? "It may be beneficial," adds Jose, "to use coatings for microscopic lenses as well as magnifiers when the patient demonstrates a significant loss of contrast sensitivity."

Can AR make devices more comfortable to use? "The better optics and illumination provided by AR coating," explains Jose, "would address the issue of long-term use of the device and reduction of fatigue."

Lens Tints and Filters

"Lighting, contrast, and glare reduction are all very important factors related to the success of low vision devices," explains Jose, so tints and filters can be important, often in conjunction with other aids.

"Reading and other near point performance in early AMD can often be improved by simply providing appropriate task lighting," explains Thomas I. Porter, O.D., who is director of the Low Vision Service at St. Louis University's Eye Institute. "Too much light, however, creates disabling glare," adds Porter. "This is where lens tints and filters help tremendously. Contrast enhancing filters have the unique ability to enhance contrast appreciation and also reduce glare."

It's no surprise that nearly all our interviewees agreed tints are by far the most important optical coating for low vision. Tints do, however, vary greatly in price and quality.

Some of the problems faced by practitioners are duplicating outdoor conditions when evaluating a patient (the patient may need one tint for indoor use and another for outside) and knowing that the color selected from a trial set will be matched accurately by the lab when a custom tint is required. Essentially, the challenge is to match the wavelength transmission.

Though certainly of interest to some practitioners, it has not been documented clinically whether or not a precision tint would provide additional benefits to low vision patients.

UV Attenuation

Patients suffering from age-related macular degeneration not only lose visual acuity and contrast sensitivity, but also experience problems with glare and photophobia. That, say half the eyecare professionals we interviewed, is where increased UV attenuation can help. That's why most glare-control products are promoted on their ability to eliminate UV as well as their stated purpose of cutting glare.

Hard Coats

Scratch resistance (hard coat) is provided on most lenses today. In many instances, you have to specially order non-coated lenses if that's what is wanted. Low vision patients may not notice scratches as readily as fully sighted persons, but durability is very important to them.

Whatever the coating, one thing that is needed is more documentation of benefits. As Jose puts it, "Without further research in this area, it is probably up to the individual practitioner and patient to determine if coatings will improve comfort and efficiency." Research aside, Jose offers one final suggestion: "Do not overlook comfort as an important factor in the successful use of low vision devices." EB