Those Darn Bifocals

This article won't be of any use to younger readers, but if you're one of the millions of Canadians wearing bifocals, and you've recently begun using a computer, you have likely cursed those darn bifocals more than once. It will be comforting to know that the problem isn't likely with you. You see, traditional bifocals were never designed for the visual demands of a computer work station. Our old, traditional bifocals (basically unchanged since Ben Franklin's day) were designed for a focal distance of sixteen inches (40 cm), and for viewing downwards at an angle of 20 to 25 degrees. That's great for sitting in an arm chair looking at a Reader's Digest, however, it just doesn't work for the video display terminal (VDT).

First of all, the VDT is typically further than the normal bifocal distance of 16 inches. Most computer screens are 20 to 28 inches from the viewer. Secondly, the viewing angle is downwards only 5 to 10 degrees, and the monitor is usually so high, that the bifocal line is right smack in the way. Glare and light reflections are the third factor to consider.

The first action you should take is a two week vacation in Maui and not look at a computer the whole time you're away. When you come back, relaxed, try and redesign the workstation, adjust your chair height, and change the keyboard and monitor positions. If the VDT is sitting on top of the CPU, try placing the CPU somewhere else (i.e.. on its side on a floor stand) so the monitor sits down on the desk. The closer together the keyboard, mouse, monitor and your copy, the less range your eyes have to move through. Feel free to experiment by placing the various components in different positions and at different angles. Please stop short of tossing the whole works out the window! In this position, you may not have any eyestrain, but the boss won't be too pleased. If a redesigned workstation doesn't fully solve the problem, then it may be worth the investment on some new glasses.

There are a number of different lens designs which can be used by the computer user. Unfortunately, most of these are specialty designs which work well for the VDT, but poorly for anything else. Just as one pair of shoes is not appropriate for dancing, golfing and announcing the federal budget, one pair of glasses can not usually be used in all visual environments. The simplest lens design is single vision, focused for the specific working distance of your workstation. With this lens you can not peer across the room at the clock on the wall waiting for the little hand to point to 5:00. Nor can you closely inspect that annoying new hangnail. However, for the computer distance, you have a large field of view, a lens that is easy to adapt to, and a nice low-cost solution. Half eyes (granny glasses), will work just as well when specifically focused for the VDT, plus give the advantage of being able to look overtop and clearly see distances (providing you have good distance vision).

If a single vision lens is unsuitable, or if you must be able to see far, near and the VDT, then one of the specialized trifocals may be the solution for you. We have a couple of lens designs here. The first is called "Executive 14". This is a trifocal with the lines going all the way across. The top lens is focused for distance (three feet and beyond), the middle lens is focused for intermediate (18" to 3') and the bottom lens is for near (14" to 18"). Rather than the middle lens being very narrow at 7mm, this lens is much deeper at 14mm. This allows adequate viewing area for the VDT distance, but the lens is typically quite heavy, and the thick lines create bothersome reflections.

The "CRT" lens is cut with a line 1/3 from the top. The top lens is good for distance and the lower part of the lens is focused for the VDT. Set into the bottom lens is a small bifocal which allows near viewing. As with the Executive 14, the field of view is good for the monitor, yet still allows other distances to be seen as well. However, this is a difficult and slow lens for an optical lab to make.

Progressives have been called no-line bifocals or trifocals, but are in reality "multi-focal". The power of the lens continually changes from full distance power to full near power without any troublesome lines. These lenses have been working very well as an "all round" choice; suitable for normal activities as well as VDT. As a draw back, they area bit more expensive than some of the other choices, and although they can be difficult for some people to get used to, the vast majority of folks do very well with these.

Special "progressives", the Technica, Office and the Access, are specifically designed for the VDT. They allow excellent fields of view for the monitor, as well as allowing distance and near viewing. However these are not general purpose lenses, and could not be worn as your only pair of glasses.

At the office most of us have to contend with not only the VDT but fluorescent lighting as well. If the glare seems to bother you, wear a visor to work one day, if eyestrain is lessened, you know the lights are partly to blame. A coating to block UV (ultra-violet) helps most people so ask for "UV-400" on your next pair of glasses. It is very inexpensive at our office. Reflections off the front and back surface of the eyeglass lens may not be consciously noticed, but overhead lights and the VDT itself can cause subtle ghost images which can be extremely annoying. Anti-reflection coatings are becoming very popular as they are very effective for these kinds of problems. However, once coated, the lens must be kept very clean, so don't get this coating if you're not scrupulous with hygiene.

So.. did I answer your question about which lens you should get for VDT use? No, I suppose I didn't. As you've learned, each lens design has its advantages and disadvantages and the only way to properly choose is by fully discussing with your eye doctor or optician, the design which will work for your particular needs. I personally recommend the regular progressive or the Access most frequently, but of course there are exceptions. Well good luck in your search for strain free computing, and remember, rest your eyes for at least one or two minutes for every 30 minutes you look at the screen.