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Contact Lenses and VDTs

BY JEFFREY ANSHEL, OD
MARCH 1999

It should be no surprise to you that many of your patients use computers regularly. Because video display terminal (VDT) use is such a visually demanding task, vision problems and symptoms are common. These problems are known as Computer Vision Syndrome (CVS).

Symptoms include eyestrain, headaches, blurred vision (distance or near), dry and irritated eyes, slow refocusing, neck or backache, light sensitivity, double vision and color distortion.

The causes of CVS can be any combination of individual visual problems and poor office ergonomics. To complicate matters, 30 million Americans wear contact lenses. Let's take a look at some concerns you should address when dealing with the VDT user who wears contact lenses.

Dry Eyes

VDT work usually requires a higher gaze angle. As we gaze higher, the eyes open wider, which results in faster tear loss and more incomplete blinks.

Contact lens wearers can be very susceptible to dry eye. If the problem is due to a dry environment, regular use of artificial tears should alleviate it.

Correction

If the patient's near or intermediate correction is different than that for distance, you may want to prescribe computer eyeglasses to be worn over the contact lenses.

For presbyopes wearing lenses for monovision, you must be aware of the working environment. For example, the distance of the VDT screen is often farther away than our usual testing distance. Determining the patient's normal working distance and assuring that the near prescription compensates at that distance is critical. Otherwise, the patient would have to lean forward to see the screen clearly. This could cause back and neck problems.

Another point of concern with monovision is the workstation setup. Many patients enter data into the computer from a hard copy. If the near lens is fit on the left eye, for example, and their hard copy is located on a document holder to the right of the screen, they'll have a big problem in viewing the copy clearly. Despite the traditional approach of fitting the dominant eye for distance viewing, you might want to question the VDT user extensively when fitting monovision.

The RGP fitting of the presbyope deserves some special consideration, too. If your choice is a translating design, you should be aware of the working distance. Also, the resting position of the bifocal line might be inadequate if the patient views his monitor high in his field of view. In general, the aspheric RGP design allows for a broader range of near viewing distances, which often include the VDT screen.

Environment

Since we don't see patients in their office, we must question them about their individual work environment.

In addition to the VDT viewing distance, critical factors include the viewing distances of the keyboard, the desk, the telephone and clients sitting nearby. The patient's ability to see these areas might require that a task-specific prescription be worn over the contact lenses.

Lighting is one of the most overlooked areas of workplace ergonomics. Glare is a significant concern for the contact lens wearer. Excessive tearing, decentering of lenses, rotation of toric lenses, poor edge quality, wide peripheral curves and other factors can lead to extraneous glare.

Even the best fit contact lenses can create a glare problem for the VDT user. With fluorescent lighting, a light rose color tint in eyeglasses can make the patient more comfortable.

Contact lenses and computers should be compatible for our patients. If we think a little more about the patient's environment, we can foresee and correct problems before they occur. CLS

Dr. Jeffrey Anshel specializes in computer vision concerns. He has written several books and practices in Carlsbad, Calif.