Ординатура / Офтальмология / Английские материалы / Diagnosing and Treating Computer-Related Visual Problems_Sheedy, Shaw-McMinn_2003
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Parasuraman A, Berry L, Zeithami V. Understanding customer expectations of service. Sloan Management Review, Spring 1991;39–48.
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Signs and Symptoms of Computer Vision Problems
Eye and visual symptoms occur whenever the visual demands of the work exceed the individual’s abilities to comfortably and efficiently deal with them. For example, gas station attendants do not complain of eyestrain. The visual demands of the tasks are simply not great enough to cause symptoms of eyestrain.
By comparison, many tasks, such as working at a computer (especially if the environmental conditions are poor), can cause symptoms in many working people because the visual demands exceed the capabilities of many of the workers. Eye-related symptoms occur in 25– 93% of computer users, as reported by various investigators (Thompson, 1998). It is clear that a large percentage of computer workers experience eye symptoms. The large range is easily understood given the considerable variability in the methods of measuring symptoms, the wide range of jobs under study, and differences in eye care availability. Older workers and worker groups with poorer eye care, poorer computer displays, and poorer office ergonomics have more eye problems. There can be large prevalence differences among individual companies and even among different departments within the same company. Computer workers also experience musculoskeletal problems such as neck, back, shoulder, and wrist aches. A study by Hales and colleagues (1994) showed that 22% of computer workers have musculoskeletal disorders. Most studies show that eye-related problems are the most frequent health-related symptoms of computer workers.
Symptoms related to work almost always occur within a certain time period after the patient starts work. They are also dose related (Gunnarsson and Soderberg, 1983)—that is, the more intense the
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36 Diagnosing and Treating Computer-Related Vision Problems
work, the more intense the symptoms. Normally, work-related symptoms go away on weekends and vacations. If the symptoms do not follow these patterns, they are probably not related to work.
The presenting symptoms can be very helpful in identifying the most likely diagnosis—whether it is a visual or environmental diagnosis. A good case history directed toward exploring the patients’ symptoms can often direct the examination and efficiently arrive at the diagnosis. This chapter focuses on the presenting symptoms of patients with computer vision syndrome. History forms and questions are provided to assist the assistant or technician in responding properly to the patient’s concerns.
This chapter also reviews the possible causes of the symptoms and how symptom analysis can efficiently direct the examination to the diagnosis. The chapter also describes how to prepare the patient for possible treatments before the examination begins.
Symptom Analysis
The symptoms that a particular computer worker has can be very helpful in identifying the most likely problem—whether the causative condition is visual, environmental, or both. Patient symptoms are most efficiently identified with a questionnaire designed for computer users. The questionnaire in Appendix 3-1 (page 44) is designed to identify the most important history information on a computer user. The categories of symptoms on the questionnaire are coordinated with the symptom categories discussed below.
Vision Symptoms
Blurred vision is a commonly reported symptom that usually points to a particular visual disorder (Box 3-1). Of course, constant blurred vision is an indication of an uncorrected refractive error or presbyopia, depending on the viewing distance at which the blur occurs. Squinting is also usually an indication of refractive error problems. Intermittent blurred vision at distance after near work is almost pathognomonic of an accommodative spasm or general accommoda-
Signs and Symptoms of Computer Vision Problems 37
Box 3-1
Visual symptoms
•Blurred vision
•Slow refocusing
•Frequently losing place
•Doubling of vision
•Squinting
•Changes in color perception
tive dysfunction. This blurred vision may only be momentary when the person looks up from his or her work or it can last for several hours after near work, causing difficulties driving home from work. If the blurred vision is intermittent at near viewing distances (slow refocusing) during near work, it almost certainly indicates an accommodative disorder such as reduced amplitude of accommodation or accommodative infacility. Testing should include amplitude of accommodation, lens flippers, and plus/minus lenses to blur binocularly (negative relative accommodation and positive relative accommodation). Sometimes a concurrent esophoria may be diagnosed as contributing to the accommodative problems.
Another cause of intermittent blurred vision at near viewing distances is dry eye. This can usually be differentiated in the history by asking the patient whether his or her vision clears when he or she blinks.
Diplopia (double vision) almost always indicates a binocular vision disorder, but careful questioning of patients or users is necessary to ensure that they are not reporting blurred vision as double vision. Intermittent diplopia that occurs after extended near work, especially if accompanied by reports of eyestrain, often indicates a convergence insufficiency. Repeated measurement of the near point of convergence should be performed and ability to comfortably maintain fixation at the near point of convergence should be evaluated.
However, patients seldom report diplopia, even if their eyes become momentarily misaligned. People are so intolerant of seeing
38 Diagnosing and Treating Computer-Related Vision Problems
Box 3-2
Ocular symptoms
•Irritated eyes
•Itching and burning eyes
•Excessive tears
•Dry eyes
•Excessive blinking
•Contact lens discomfort
•Sore or hurting eyes
double that as soon as it happens they close their eyes or in some other manner quickly discontinue the viewing situation that results in double vision. The lack of diplopia as a symptom does not in any way rule out the possibility of a binocular vision disorder.
Color perception problems were more frequent with older monochrome video display terminals; however, they can still occur in situations in which the user spends considerable time viewing a saturated color. This problem is managed by changing to less saturated and dimmer colors on the computer display. See Chapter 10 for further information on this topic.
Ocular Symptoms
In computer workers, any of the symptoms listed in Box 3-2 typically indicate dry eyes (see Chapter 7). Computer workers are particularly prone to having dry eye problems because their blink rate is significantly reduced and their horizontal gaze angle at the screen results in an ocular aperture which is larger than when looking down and reading a book, thereby resulting in increased tear evaporation. A report of watery eyes is often the result of reflex tearing secondary to irritation caused by dry eyes. Tear film quality and tear quantity should be investigated. Many patients with marginal dry eyes have no symptoms during other daily activities, but have significant dry eye symptoms when working at the computer.
Signs and Symptoms of Computer Vision Problems 39
If a patient reports symptoms of dry eyes, ask whether the computer screen is too high (the center of the screen should be 4–9 in. below the eyes), whether the office is low in humidity (particularly a problem during cold weather), or if he or she is seated with a vent aimed toward his or her eyes. Affirmative
answers to these questions identify environmental problems that can be important in resolving the patient’s symptoms.
Itching eyes often indicate seasonal allergy problems and should be pursued with further questions. Also, irritated or burning eyes in the absence of dry eye findings may indicate airborne toxicants in the office environment. This is further indicated if other employees in the work area have similar symptoms.
Asthenopic Symptoms
The group of symptoms listed in Box 3-3 includes eyestrain, headaches, and eye fatigue. This set of symptoms is the least diagnostic group of symptoms; there are numerous diagnostic conditions that can cause these symptoms. These conditions include uncorrected refractive error, presbyopia, accommodative disorders, esophoria, convergence insufficiency, and poor ergonomics such as glare from overhead lights.
A report of eye or general fatigue associated with near work can often indicate a convergence insufficiency. If the patient is exophoric, carefully evaluate the base-out to blur findings and the near point of convergence. If the patient is noticeably strained during near point of convergence testing, ask whether he or she feels the same strain when working. Very often, the patient will report that the strain is identical, thereby confirming the diagnosis in both the doctor’s and the patient’s mind. This facilitates patient
motivation for the most effective treatment—convergence training.
It is unfortunate that a patient report of eyestrain does not provide a strong clue to any diagnosis, because eyestrain is the most commonly reported symptom by patients working at computers. Additional questioning can often elicit more specific descriptions of the symptoms.
40 Diagnosing and Treating Computer-Related Vision Problems
Box 3-3
General eye symptoms—asthenopia
•Eyestrain
•Headache
•Eye fatigue
•Tired eyes
Light Sensitivity Symptoms
Many patients report sensitivity to lights (especially fluorescent lights) or that flickering light bothers them (Box 3-4). Iritis can cause these symptoms and should be ruled out.
The most common cause of light sensitivity problems among computer users is lighting in the work environment. It is common for computer workers to experience discomfort glare from overhead fluorescent lights or from bright windows. This is due to the fact that computer workers have a higher gaze angle in the room compared to other desk workers, resulting in the bright lights being closer to central fixation. This condition can be diagnosed by having the patient shield his or her eyes from offending light sources. An immediate sense of relief indicates that the patient is experiencing glare discomfort, and he or she should either eliminate the glare source or wear a visor. Glare discomfort can be demonstrated in the office (in a location with bright overhead lights) so that the patient knows what to look for back at his or her own desk. Decreasing the brightness of the computer screen
Box 3-4
Lighting symptoms
•Flickering sensations
•Glare
•Light sensitivity
Signs and Symptoms of Computer Vision Problems 41
(thereby decreasing sensitivity to flicker) or prescribing a pink tint lens can also help alleviate the symptoms of light sensitivity.
Some patients report flicker of the computer display. This is possible if the patient uses a cathode ray tube (instead of a liquid crystal display) and the refresh rate is relatively low—say 60–70 Hz. These symptoms can often be eliminated by adjusting the refresh rate higher, decreasing the display brightness, or both. See Chapter 10.
In some situations, a binocular vision disorder can result in light sensitivity. Light sensitivity occurs because it is difficult to suppress an image in brighter light. This failure to suppress causes symptoms from the attempt to gain and maintain binocularity. The difficulty of suppressing in bright light is why an intermittent strabismic squints in the sun but not indoors. The squinter often has no idea he or she is closing one eye. Visual therapy improves the ability to compensate and fuse, thereby eliminating the need to suppress to avoid binocular problems.
Musculoskeletal Symptoms
Many patients who maintain the same posture for extended periods of time report neck aches, shoulder aches, or backaches. This is common for many computer workers as well as for microscopists, assembly line workers, and others engaged in repetitive work. These musculoskeletal symptoms result from assuming a less than optimal posture for extended periods of time, which causes tonic stress in the musculature (Box 3-5).
Box 3-5
Musculoskeletal symptoms
•Neck or shoulder tension, pain
•Back pain
•Pain in arms, wrists, or shoulders
42 Diagnosing and Treating Computer-Related Vision Problems
These problems are often related to the eyes. It is commonly recognized that “the eyes lead the body.” For visually intensive tasks, the body locates the eyes at a position where they can comfortably and efficiently perform the job; this is often accomplished by creating awkward posture that results in musculoskeletal problems.
If multifocal lenses do not provide the correct lens power at the correct location in the lens for the patient’s work, they cause the person to assume an awkward position and thus cause musculoskeletal symptoms. It is important to know the viewing distances and locations of the patient’s work (see the questionnaire in Appendix 3-1, page 44) so that the proper prescription and lens design can be made. It can be very helpful to have patients bring measurements of their work location with
them to the examination, but it is often easier to have patients go back to their work area and return with the critical measurements.
If the patient’s workstation is not properly set up for him or her, it can easily result in these musculoskeletal symptoms. For example, if the patient’s computer screen is too high or off to the side it can result in neck aches, backaches, or both. Shoulder aches are often caused by keyboards that are too high.
Box 3-6
General symptoms
•Tension
•Excessive physical fatigue
•Irritability
•Increased nervousness
•More frequent errors
•General fatigue, drowsiness
Signs and Symptoms of Computer Vision Problems 43
Other Symptoms
Many computer workers have stressful jobs, often compounded by personal problems. Symptoms of tension, irritability, and others are common and usually are not related to eye problems. However, it is not uncommon for eye-related problems to work in synergy with other life and work stressors to produce these general symptoms (Box 3-6).
References
Gunnarsson E, Soderberg I. Eye strain resulting from VDU work at the Swedish Telecommunications Administration. Appl Ergon 1983;14:61–69.
Hales TR, Sauter SL, Peterson MR, et al. Musculoskeletal disorders among visual display terminal users in a telecommunications company. Ergonomics 1994;37: 1603–1621.
Thompson WD. Eye problems and visual display terminals—the facts and fallacies. Ophthalmic Physiol Opt 1998;18(2):111–119.