Lenses for computer users
From headache to eyestrain, many symptoms of CVS can be cured by variable focus lenses
By Joseph L. Bruneni
Illustrations by Dan McGeehan

Computer vision syndrome...it's a multi-faceted combination of eye and vision problems related to near work, especially computer use. But its symptoms extend far beyond the eyes, and patient complaints can include: Eyestrain or fatigue, headaches, slowed distance focusing, dry eyes, and neck or shoulder pain.

One solution is a totally new category of lens called "variable focus." They fall under the general classification of progressive addition lenses, but are different from conventional PALs. They have many applications, but the most common one is to satisfy the unique visual needs of those who work with computers.

Addressing these complaints requires a multi-faceted approach by the eyecare professional. A routine refraction and a conventional pair of glasses seldom fully resolve the problem. Instead, the patient should be told in advance that computer work often requires dedicated eyewear. Once that issue is acknowledged, meeting on-the-job visual requirements becomes a relatively simple task.

CAUSES AND EFFECTS

Problems associated with CVS often occur in offices that were poorly designed for the visual demands of computer use. Problems include poor lighting, reflections bouncing off monitors, and incorrect monitor positioning.

Usually the screen is set too high, so most of the operator's work takes place at intermediate distance. For PAL wearers, problems arise when the patient tries to look at the monitor through the bifocal near area or an intermediate corridor.

This is aggravated by the way our brains work. The brain determines how much the eyes need to focus by visual clues such as contrast between objects or the well-defined edges of objects. When we read, our eyes benefit from good contrast between black print on white pages.

But when that contrast is absent--as is often the case with computer use--there is less accurate focusing, and the ciliary muscles must work harder to focus, causing fatigue.

Then there's the problem of the computer screen itself, which is made up of pixels of light. Each pixel is bright in the center and dims toward the edge.

SOLVING THE PROBLEM

With early computers, it was believed that lens tints could help reduce visual complaints. A lens tint corresponding to the color of the monitor would be selected to enhance contrast. With today's full-color monitors, it's generally agreed that lens tints aren't necessary.

Another early concern was ultraviolet rays emitted by vision display terminals (VDTs). It is now generally accepted that UV radiation from monitors is well below allowable standards. If a patient is concerned, however, use lenses with built-in UV protection or add a UV treatment to alleviate this worry.

Another component in CVS involves reflected glare from monitors. The best way to eliminate this is to reposition the monitor or overhead lights. When this is not practical, monitors can be fit with an anti-reflective glare screen. Though AR coatings actually increase the amount of reflected glare reaching the eyes, AR provides other benefits and is usually a useful addition to your patients' computer eyewear.

It's important to explain to patients that solving their computer visual problems often requires the use of eyewear specifically designed for computer use and other near tasks. Patients who don't require a distance correction and are willing to take off their glasses when away from the computer may find that single vision lenses are a good answer.

There are other options, however, that may better serve the user's needs.

PRESBYOPIC SOLUTIONS

For older patients, the critical issue is placing the computer add power in the line of sight. There are four types of lenses that can accomplish this: Single vision, bifocal, progressive, and variable focus lenses.

Single vision lenses: If computer use is constant, and the wearer can tolerate distance blur, single vision lenses can work. The advantage is that they provide a wide field of vision with no need to move the head vertically to find the right power. However, they are not the best choice for moderate to advanced presbyopes.

Bifocals: The computer Rx can be incorporated into bifocals with the seg positioned for viewing the monitor. However, clear vision will be limited to near and distance.

There are, fortunately, PALs designed specifically for computer work. They typically have a small distance window at the top, which allows the intermediate and near areas to be wider.

Variable focus: These lenses decrease in power as wearers look up and provide distortion-free near and mid-range variable vision. Their simplified progressive design reduces distortion in the periphery.

Usually available in one, two, or three variations called power shifts, selection depends on add power. They differ in design and concept among manufacturers, and laboratories can provide you detailed fitting information for the brand you select.

The plus power in the top portion of the lens is reduced by a set amount. For example: A typical lens design that comes in three power shifts will reduce the plus power in the top portion by 0.75D, 1.25D, or 1.75D.

At the fitting cross, the power will be 50 percent of the specified power shift. Also, the lenses are decentered for right and left eyes.

FITTING TIPS

As you would with PALs, dot the center of the pupils on the frame, and take a monocular PD with a pupilometer. Be sure to pay attention to the manufacturer's fitting advice because there are subtle design differences between manufacturers, and some variable focus lenses are intended to be fit at near PD, while others are to be positioned at distance PD.

Once the fitting cross is marked, it can be adjusted to compensate for monitor placement. For example, if a patient's monitor is positioned high on the desk, move the fitting cross upward slightly in the frame, making sure there is enough vertical height. Keep in mind that most variable focus lenses require at least 13mm from the fitting cross to the frame's upper rim. And, there should be at least 16mm from the fitting cross to the lower rim (overall "B" measurement should be 29mm or more).

The lab should receive the patient's distance Rx, normal reading add, and computer add power (if a special computer testing device was used during the refraction). The lab will select the correct power shift.

Most jobs will be returned with the fitting cross indicated and a circle marking the near add power. To verify lenses, check the add power in the circle and the PD.

Almost all computer glasses will represent a second pair of glasses for the patient. This is proving to be an economic benefit for the industry, and, after years of looking for ways to promote second pairs, it now seems to be that the viable answer is task-specific eyewear.

Most glasses dispensed for computer users are task specific, and while much of the computer eyewear market is aimed at older presbyopes, there is an equal need for dedicated computer glasses for younger patients as well.

The fact that a second pair is needed for normal everyday use is one reason why so many companies are concentrating on this profitable lens.

Another is that variable focus lenses are useful for more than just computer users. In fact, an alternative term for them is "indoor" or "room" lenses. And, the fact that these reading glasses permit wearers to walk through the office or home without changing glasses adds hundreds of other uses for these lenses.

A market this big should excite everyone in the optical industry. So why aren't labs processing more orders for these lenses? The answer is simple. Many eyecare professionals don't know about them or don't understand when they should be recommended.

One solution? Many labs routinely conduct in-office continuing ed for accounts, and variable focus lenses are an ideal subject for these courses.

Every PAL wearer should be offered a second pair of glasses with variable focus lenses. As one long-time progressive wearer who recently was fit with variable focus glasses, puts it: "Slipping on my indoor glasses when I sit down to read a book or newspaper is like putting on a favorite pair of house slippers after working on my feet all day."