- Asthenopia represents a subjective complaint of uncomfortable, painful, and irritable vision. There are 24 different types of asthenopia based on various causes. Because of its subjectivity, however, it can have a myriad of meanings to any number of people. Asthenopia can be caused from some underlying conditions such as focusing spasm, different vision in each eye, astigmatism, hyperopia, myopia, excess light, voluntary focusing, eye coordination difficulties, and more.
- Because computer use is such a high visually demanding task, vision problems and symptoms are very common. Most studies indicate that computer operators report more eye-related problems than noncomputer office workers. A number of investigators have indicated that visual symptoms occur in 75 to 90% of computer workers (Anshel, 2005). In contrast, a survey released by the National Institute for Occupational Safety and Health (NIOSH) showed that only 22% of computer workers have musculoskeletal disorders.
- A survey of optometrists (Sheedy, 1992) indicated that 10 million primary care eye examinations are given annually in this country, primarily because of visual problems at computers. This study eventually culminated in the compilation of the series of symptoms that are now collectively known as computer vision syndrome (CVS). This condition most often occurs when the viewing demand of the task exceeds the visual abilities of the computer user. The American Optometric Association defines CVS as that “complex of eye and vision problems related to near work that are experienced during or related to computer use.” The symptoms can vary but mostly include
eyestrain, headaches, blurred vision (distance or near), dry and irritated eyes, slow refocusing, neck and backache, light sensitivity, double vision, and color distortion.
It is imperative to elicit a thorough case history to distinguish the type of headache involved. The patient should be queried about the time of onset, location of the pain, frequency, duration, severity, and precipitating factors such as stress, certain foods or medications. Associated signs and symptoms such as nausea, vomiting, light sensitivity, and noise sensitivity should also be noted.
Computer workers most likely get tension-type headaches. These can be precipitated by many forms of stress, including anxiety and depression; numerous eye conditions, including astigmatism and hyperopia; improper workplace conditions, including glare, poor lighting, and improper work-station setup. These types of headaches are mild to moderate in intensity, often occur on either or both sides of the head, are not aggravated by physical activity, develop during the early to middle part of the day, last from 30 minutes to the rest of the day, and are relieved by rest or sleep. Chronic tension headaches vary somewhat from this but have the same overall symptoms and occur much more frequently.
Visual and environmental conditions are the first places to look for a solution to a headache problem. If all obvious factors have been considered, medical management is in order, often starting with a complete eye examination to rule out a visual cause.
Visual acuity is the ability to distinguish between two distinctive points at a particular distance. This requires the image formed on the retina to be well circumscribed and distinct. If the image focuses in front of or behind the retina, it will strike the retina in an unfocused state, creating the subjective
symptom of blur. This process is true for all distances with the viewing range of the human eye, which we routinely consider to be from within 20 feet to 16 inches.
A condition known as transient myopia has been shown to be more prevalent in a population of computer users. This is a condition in which a person exhibits myopia toward the end of the day but not at any other times. Many times, the myopia is not present early in the day or on weekends.
Glare is also a concern because of the eye attending to the glare image rather than the screen image. If a specular reflection is noticeable on the screen, the eye will attempt to focus on it. The image of the glare source will appear to be somewhere behind the screen (much as your image is reflected in a mirror) and the screen image can appear blurred. This can become more noticeable as computer usage time is increased.
The lachrymal glands secrete the tears that cover the eye surface and keep the eye moist, which is necessary for normal eye function. The tears help maintaining the proper oxygen balance of the external eye structures and to keep the optical properties of the eye sharp. The normal tear layer is cleaned off and refreshed by the blinking action of the eyelids.
The blink reflex is one of the fastest reflexes in the body and is present at birth. However, our blink rate varies with different activities — faster when we are very active, slower when we are sedate or concentrating. Yaginuma et al. (1990) measured the blink rate and tearing on four computer workers and noted that the blink rate dropped very significantly during work at a computer compared with before and after work. There was no significant change in tearing. Patel et al. (1991) measured blink rate by directly observing a group of 16 subjects. The mean blink rate during conversation was 18.4 blinks per minute, and during computer use it dropped to 3.6 — more than a five-fold decrease.
Tsubota and Nakamori (1993) measured blink rates on 104 office workers. The mean blink rates were 22 blinks per minute under relaxed conditions, 10 blinks while reading a book on a table, and only 7 while viewing text on a computer. Their data support the fact that blink rate decreases during computer use, but also show that other tasks can decrease the blink rate.
Computer Vision Syndrome (CVS)
Definition: CVS is a series of signs and symptoms that are common to those who experience computer-related eye discomfort.
Etiology: The main causes for the visual complaints are a combination of individual visual problems and poor visual ergonomics either at home or at work, or even in both environments.
Most frequent Signs and Symptoms
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