By the Ophthalmological Society

Computers and your eyes

To date, the overwhelming evidence is that there is no radiation risk from video display terminal (VDT)/cathode ray tube units and that it is concern about radiation risk that overwhelms the worker, along with other possible causes of physical discomfort or harm in this work situation. The presence in some workers of symptoms of ocular or general fatigue have become intermixed with an understandable concern about radiation, so that all disability or discomfort encountered is or tends to be blamed on radiation.

This situation is better understood now than it was even 3 or 4 years ago, but there is still much reluctance in the workplace to make adequate allowance for such factors as the sound background, the need for well-designed equipment, variety in tasks, good illumination and proper air exchange, and finally, the value of a good eye examination by an understanding examiner.

The situation regarding background radiation and radiation "hot spots" is less clear because the investigation of this aspect has not been consistent or thorough. However, this possible source of risk is more or less universal and therefore is not restricted to any group, such as VDT workers. It is hoped that there will be further monitoring of background radiation levels in all situations where there is any suggestion that there could be a hazard.

The ophthalmologist should be reasonably well informed about symptoms of visual difficulty, ocular fatigue and general fatigue that may relate to this type of work. The ophthalmologist should keep in mind Hans Selye's demonstrated relationship between stress and disease when helping to solve the patient's problem or when asked for advice by industry or by those interested in occupational health problems.

Reducing eye strain - how to protect your eyes

Your eyes water, your eyelids twitch, the part of your forehead around your eyebrows seems to ache, and you notice a burning sensation when you close your eyes. You're suffering from eye strain. It's a common affliction that can occur after the eyes are taxed for a prolonged period-for example, after hours of close work or driving.

But you can reduce eye strain by taking simple precautions.

Reading

Hold the reading material about 30 to 40 centimetres away from your eyes. Ensure you have adequate soft light coming from a source behind or beside your left shoulder-use a lamp with a 60 to 100 watt bulb. Take a break every hour or so by looking at distant objects for three or four minutes. Follow the same guidelines for other close work, such as sewing, knitting and drawing.

Television

While watching television, the lighting in the room should be appreciably dimmer-by about 50 percent-than the illumination of the screen. Ensure that the lighting doesn't reflect on the screen or cause a glare. Don't watch in darkness-the contrast in light is too sharp. Avoid viewing from an angle. Sit in front of the set at a reasonable distance about four or five times the width of the TV screen-e.g., for a 50 centimetre (20 inch) screen, sit about two to two and a half metres away. Those with poorer sight may need to sit closer.

Despite what you may have been told as a child, television will not damage a child's eyes. In fact, children can focus up close without eye strain (fatigue) more easily than adults.

There is no evidence that this damages their eyes and it is a habit that usually disappears with age. Occasionally, children with near-sightedness sit close to the television in order to see the images more clearly. An ophthalmologist can diagnose this condition and correct it by prescribing suitable glasses.

Video display terminals

The lighting in the room should be soft and not as bright as the screen. Put the screen in a spot where there is no glare from the windows or lights. Sit at least 50 centimetres from the screen, and position it so that you look downward at it, at an angle of about 20 degrees. When you're working for a steady period, take occasional breaks from the screen and relax your eyes by looking at a distance for a few minutes.

If your eyes feel dry after a prolonged period in front of the screen-or after any other visual activity-try using an over-the counter teardrop product containing the wetting agent polyvinyl alcohol or methylcellulose.

Driving

On bright or hazy days, wear sunglasses to protect your eyes from glare and harmful ultraviolet rays. If you're on a long trip, stop every few hours to rest your eyes and stretch.

Rest usually alleviates eye strain. But if you suffer prolonged discomfort or notice a marked change in your vision, you should immediately have an eye examination.

UV rays

Sun worshippers, cover your eyes!

Studies have shown that permanent damage to the eyes can result from prolonged exposure to the sun without adequate protection. Ultra violet (UV) light is the component of sunlight most responsible for eye damage. Excessive exposure, especially from light reflected from sand, snow or pavement, can produce a burn on the surface of the eye. Like a sunburn on the skin, eye surface burns are usually painful, but temporary.

Of more concern is the cumulative damage of repeated exposure that may contribute to chronic eye disease. UV exposure can affect not only its surface, but also its internal structures (the lens and retina).

UV light is a risk factor in the development of pterygium (a growth that invades the corner of the eyes), cataracts (clouding of the lens) and macular degeneration (breakdown of the macula).

Those at risk include people who spend a lot of time in the sun, those who live at high altitudes or near the equator, and those who take photosensitizing drugs such as psoralens (used to treat psoriasis), tetracycline, doxycycline, allopurinol or phothiazine.

During cataract surgery, the natural lens is removed and replaced with a synthetic lens. Newer intraocular lens implants filter UV radiation. This eliminates any concern about UV eye protection after cataract surgery.

To protect your eyes from the sunlight, it is recommended that you wear a wide brimmed hat and sunglasses that filter out 99-100 per cent of the UV light.

Sunglasses

Here are a few tips to help you choose a pair of sunglasses that can protect your eyes from the damage that can be caused by prolonged exposure to sunlight.

First, look at the label. Although universal standards are not in place, most manufacturers label their products stating their protective ability. The Canadian Ophthalmological Society recommends that glasses block 99-100 per cent of UV light (both UV-A and UV-B).

If you spend a lot of time in the sun, it is recommended that you buy wrap-around glasses to prevent the sun from entering your eyes from the sides.

Don't be deceived by color or cost. Dark lenses do not necessarily mean good protection. Also, expensive glasses do not guarantee good protection. Price may be an indication of better quality or durability, but more often, it is a reflection of current fashion.

Seasonal depression, jet lag and light therapy

As many as 10 per cent of Canadians may suffer from some sort of seasonal depression caused by sunlight changes. Commonly called the "winter blues", symptoms can include low energy, excessive sleep, over-eating, weight gain and even severe depression. These effects are usually caused by what is commonly referred to as a malfunction of the body's clock. Light therapy may help these people as well as those who work shifts and those who suffer from jet lag.

As well as sending images to the brain, the eyes also tell our pineal gland, a small pea-sized gland located in the brain, when the day is over. The gland then induces drowsiness by secreting melatonin. This gland also influences moods, hunger and metabolism. (It has been determined that melatonin is used as a marker for the body's internal clock.)

Doctors have learned to treat this seasonal depression and jet lag by using a simple device called a light box. Because the timing, intensity and duration of the light all play a role in the treatment of each individual case, it is important to stress that the light therapy must be administered by a medical doctor or therapist. Some cases of corneal burns have been reported by people who have tried to treat themselves.

If you think light therapy may help you, consult your physician.

Commercial tanning facilities

There is increasing evidence that the use of tanning salons and sun lamps can cause ocular damage. The Consumers' Association of Canada (CAC) is concerned about the lack of regulation of the use of radiation-emitting devices found in commercial tanning studios.

The CAC points out that although the equipment recommended for commercial tanning facilities is manufactured according to the specifications outlined in the Radiation Emitting Devices Act, many operators are using the equipment incorrectly and proper eye protection is not required by law. The Canadian Ophthalmological Society endorses the CAC position.

The Health Protection Branch of Health Canada has monitored the use of sun lamps for some time, as several thousand people are treated each year in emergency departments for the acute ocular effects of sun lamp burns. There is increasing evidence that more serious long-term ocular damage may also result.

The major problem arises from the fact that although the manufacture of the lamps is adequately controlled by federal regulation, the implementation of the tanning process is virtually unregulated. Tanning operations have to meet sanitation regulations, but health inspectors have no power to ensure that owners use the correct bulbs, make clients wear protective goggles, limit exposure times or screen clients for photosensitizing diseases or drugs.

DISCLAIMER: All content is provided for information and education and not as a substitute for the advice of a physician. The Canadian Ophthalmological Society assumes no responsibility or liability arising from any error or omission or from the use of any information contained herein.