Diagnosing, treating CVS relies on good case history

Jeffrey Anshel

Millions of people around the world are using computers, not only for business but also for recreation. Predictions indicate that 50% of the working population will be using computers by the year 2010, and 20% of those people will be older than 55 years. Approximately 820 million people use the Internet worldwide, with an expected explosion of users to more than 1 billion in the next few years.

This amount of computer use can lead to eye problems. According to Sheedy, more than 20% of those patients who request an eye exam due to computer stress do not receive an adequate resolution to their problem.

Corporate America is slowly becoming aware of this issue. Ergonomics addresses human function in relation to working conditions and is now a division of environmental health and safety within many companies. However, these environmental specialists are not trained in how the visual system functions — thus it remains within our realm of expertise to deal with this condition.

What is computer vision syndrome?

The American Optometric Association defines computer vision syndrome (CVS) as “the complex of eye and vision problems related to near work, which are experienced during or related to computer use.” Computer users experience a series of signs and symptoms created by this type of nearpoint activity. Several studies indicate that computer users complain of eyestrain as their primary symptom, whereas people report musculoskeletal disorders less often. Visual problems are painless and develop more slowly, allowing computer users to continue their work despite these subtle changes.

The first line of attack to this problem is to ask the right questions. I cannot overemphasize the importance of a good case history. It is critical that your patients complete a questionnaire that asks for specific working distances to their display screen, as well as other viewing distances and environmental factors.

Three factors contribute to CVS development: the refractive condition of the patient’s eyes, his or her physical working environment and the patient’s work habits.

Symptoms of CVS

CVS symptoms include eyestrain, blurred near or distance vision, headaches, dry or irritated eyes, neck or backaches, light sensitivity or double vision. Any combination of these symptoms may be present and should not be taken lightly when examining a patient with these complaints.

Eyestrain is one of the most common patient complaints. While we are still not certain exactly what eyestrain is, it certainly indicates that a visual problem is causing discomfort on some level and must be addressed. Blurred vision — at near or distance — is a deeper manifestation of a visual problem. Over-accommodation can cause distant objects to become blurred, usually immediately after extended computer use.

Headaches are the number one complaint of eye care patients. Computer users are more prone to headaches due to the awkward head position required to perform their work.

Because vision is our dominant sense, we will adjust our body posture to adapt to any eye dysfunction. This will make it easier for our eyes to function more efficiently. Body posture during computer work is an area that we must consider along with the usual visual conditions.

Several visual conditions can contribute to CVS, including dry eyes, accommodative disorders, binocular vision dysfunction, presbyopia and various refractive states. Each may contribute to the severity of CVS and we must address each thoroughly to correct the problem.

Patients with dry eye complain of red, itchy, irritated or dry eyes. If the patient wears contact lenses, these problems may seem more severe. The causes of dry eyes vary, but most often a blink rate decrease can be a contributing factor. Because most computer users place their monitors on top of their CPU, they tend to have a straight-ahead view at the screen, allowing more tear evaporation. Dry office environments can also contribute to dry eye problems.

To resolve dry eye, the patient should lower the monitor position to allow the lids to blink easier and to reduce the exposed ocular surface. If the patient has the option, using a humidifier might also help. If the patient is a contact lens wearer, consider using a lens material that maintains moisture levels throughout the day as well as regular lubrication.

While we normally measure accommodative amplitude, the facility of accommodative function is a key finding for the computer patient. A practical method to test patients involves simply alternating +/- flipper powers and judging the response of the patient — either quick and confident or slow and unsure. This can provide valuable information in a short time. Most often, performing an accommodative exercise and taking regular breaks will help resolve this problem.

An example of an accommodative exercise is called “accommodative rock,” where the patient alternately views nearpoint and distance targets, clearing each as quickly as possible.

Glare from lights and windows on the computer screen: Monitors should be positioned to reduce glare from room lighting.	Using a standard bifocal at the computer: Most occupational progressive lenses are prescribed as near-point prescriptions with a “degression” in the upper portion of the lens.
Lights too bright: The overhead lights need to be dimmed.	Extremely high monitor: Monitors should be placed lower so users can view them in a downward gaze without tilting the neck. Images: Anshel J

Choosing vision correction

Because computer use is such a unique viewing situation, it requires special consideration for the type of lenses optometrists should prescribe. In general, all-purpose “street wear” types of lenses most often do not work properly for the computer user, especially if he or she is presbyopic. While single-vision lenses are the standard for near-point viewing, more recently developed occupational lenses have shown more promise in allowing the computer viewer to see the entire work area more efficiently.

Several different occupational progressive lenses are now available to resolve the various viewing situations. Most are prescribed as near-point prescriptions with a “degression” in the upper portion of the lens. The amount of degression varies with the power of the normal add, which relates to the patient’s existing accommodative ability. Most companies have a standard nomogram for these lenses, and the lab can manufacture them by writing the standard distance prescription with add. Ensuring that the patient understands the use of the lens is also a critical component to successfully fitting this lens type.

Lens tints have been included in computer viewing prescriptions for many years. Because the early monitors had poor visibility and letters of varying colors, a rationale came about to use tints that enhanced the letters. To date there has been no scientific basis for selecting various tints for computer display viewing. However, because most offices are lit with fluorescent lighting, a slight rose color will help offset the “greenish” tinge of color distribution from this type of lighting.

Antireflective coatings

While an antireflective coating generally improves visual comfort and clarity, especially in low-lighting situations, it does not resolve glare that originates from the display screen itself. It should be made clear to the patient that screen glare is a separate issue and must be dealt with independently.

Just like all electrical equipment, computer monitors generate UV-range radiation. However, most of the UV emanates from the back and sides of the unit, where most of the electronics originate. The small amount of UV that comes through the screen face does not pose a threat to the computer user.

In light of this information, computer users need not use a UV inhibitor in their computer glasses. And with the advent of the newer LCD flat-panel displays, all radiation issues should become obsolete since these do not radiate any significant amount of any form of radiation.

Environmental, ergonomic factors

As indicated earlier, ergonomics addresses the relationship between humans and their work. Environmental influences can have a dramatic influence on which lens prescription should be adopted, as well as the power to be used. In general, the patient should make environmental changes before the optometrist prescribes lenses for office use.

The patient needs counseling on the proper viewing distance and angle for the computer. We generally recommend at least a 24-inch working range with the center of the screen at a downward viewing angle of 15º to 20º. Most patients will understand the idea if you have them look over the top of their display screens in a straight-ahead gaze.

Room lighting is critical to display viewing. Many patients will also view their monitors at a higher elevation, which can allow extraneous light to enter the eyes, causing direct glare. If windows are present, the lighting situation becomes more complex due to a constantly changing light source and more glare. We recommend that patients not place the monitor directly in front of an unshielded window because their eyes will adapt to the outdoor brightness and not to the screen. Using task lighting is critical because most workspaces have been designed for paper-based tasks rather than screen-based.

Anti-glare filters

Because the display screen is made of glass that causes reflections, we need to minimize reflections. In general, the glass circular polarized type best filters glare and still allows enough light through the filter if the patient is using a CRT (deep) monitor. LCD displays use polarizing technology, so this type of filter is not an option. However, while the patient may not notice as much of the specular-type of glare, a more diffuse glare can cause some image degradation. Using a privacy filter will reduce glare and restrict others from viewing potentially sensitive information. This type of filter is suggested to comply with HIPAA (Health Insurance Portability and Accountability Act).

General recommendations

Computer viewing is restrictive, and the user often stares at the screen for hours at a time. The constant staring, lack of blinking and static accommodative posture is detrimental to the visual system and creates much stress. Counsel your patients to take breaks, blink often and keep breathing. I most often term this the “3-B Rule:” blink, breathe and break. Patients remember this easily and can incorporate it into their routines. For taking breaks, I most often recommend the “20/20/20” rule: Every 20 minutes, take 20 seconds and look 20 feet away.

The solution to CVS is simply a combination of good basic eye care, good visual/workstation ergonomics, a good optical correction and controlled environmental factors. It just takes a short amount of time to find these problems, and the resolution can be simple and effective.

For more information:

Jeffrey Anshel, OD, has written numerous articles regarding nutritional influences on vision, stress factors that affect visual performance and computer vision concerns. Dr. Anshel is the principal of Corporate Vision Consulting, where he addresses the issues surrounding visual demands while working with computers. He has published several books, including Smart Medicine For Your Eyes and his latest, Visual Ergonomics Handbook. He also offers on-site consultations and seminars to corporations related to visual stress in the workplace. Dr. Anshel maintains a private practice in Carlsbad, Calif. He can be reached at Corporate Vision Consulting, 842 Arden Dr., Encinitas, CA 92024; (760) 944-1200; e-mail: eyedoc@adnc.com.

References:

• American Optometric Association. Computer vision syndrome. Available at www.aoa.org/x5374.xml. Accessed August 8, 2007.
• Sheedy JE. Vision problems at video display terminals: A survey of optometrists. J Am Optom Assoc. 1992;63:687-692.