Computer Vision Syndrome
[Hazards 58, April/June 1997]

The UK's 5.5 million VDU users risk having their eyes screwed up

So, VDUs don't permanently damage your eyes? That doesn't mean screen-related eye problems aren't putting your health and even your life at risk, Hazards has found. Recent international research suggests screen-based work can have short-term but potentially serious effects on eyesight.

This is old news to the UK's 5.5 million hardened VDU users. A survey by Dollond and Aitchison, Europe's largest optical group, found over 70 per cent of those questioned expressed concerns that prolonged VDU work could affect their eyesight. Four out of every ten who used computers stated that they had experienced sore eyes from staring at computer screens for too long.

And respondents to the TUC's 1996 safety reps' survey indicated that screen-related eyestrain was up by 29 per cent since 1992.

Short-sighted

The March/April 1997 edition of Journalist, the magazine of the National Union of Journalists, gives the Health and Safety Executive's position: "There is scientific evidence that VDU work does not cause permanent eye damage," said an HSE spokeswoman.

"Studies have examined the incidence and prevalence of eye dysfunction and disease in connection with VDU use. These studies did not demonstrate any links… though they did confirm the well known problem of temporary visual fatigue."

But it is the temporary visual effects, recently confirmed in US research, that can cloud the vision for most of the waking - working - hours of an over-stretched employee.

Simon Pickvance, a Sheffield Occupational Health Project adviser who has interviewed thousands of workers during an 18 year stint advising patients in general practice, says: "Patients using VDUs a large part of their working day frequently report their eyesight is quite badly affected at work and for some time afterwards."

It is during those periods when your eyes are working seriously below par, you could be at real of risk of anything from a VDU-induced headache to a VDU-induced accident, he says. "Reversible eye problems caused by screen-based work are reversible occupational health problems, not no problem at all."

However, an HSE contract research report, Evaluation of the Display Screen Equipment Regulations 1992, published in February 1997, reveals that only one in five VDU users - fewer than 1 million workers - have exercised their legal right to free eye tests since the regulations took effect in 1993.

Under a third of the companies surveyed by the Institute of Employment Studies for HSE had provided eye tests for eligible staff.

Eye complaints

VDU-related temporary visual impairment in now an officially recognised occupational health problem in the US. The American Optometric Association has labelled the condition "computer vision syndrome" (CVS).

It says CVS can include any or all of the following symptoms:

• Temporary myopia, the inability to focus clearly on distant objects for a few minutes to a few hours after using the computer;

• Eyestrain or eye fatigue, a tired, aching heaviness of the eyelids or forehead;

• Blurred vision for near or far objects, and sometimes double vision or after images;

• Dry, irritated or watery eyes;

• Increased sensitivity to light; and

• Headaches, neckaches, backaches and muscle spasms from holding the body in awkward positions to maintain a desirable angle between eyes and screen.

A number of workplace factors can lead to CVS:

• Poor position in relation to the computer;

• Lighting that produces glare or reflections, fuzzy images or images that are too dim or too bright;

• Failure to blink often enough to moisten the surface of the eyes;

• Use of corrective lenses that are inappropriate for the user's position and distance from the screen;

• Minor visual defects that might go unnoticed if not exaggerated by intense computer use.

HSE and the British College of Optometrists accept this last point - unnoticed eyesight flaws that had caused no problems previously can become very troublesome when a person becomes a VDU user.

And Dr Kent M Daum of the University of Alabama School of Optometry, quoted on 7 August 1996 in the New York Times, said his research had shown that minor and otherwise unnoticed refractive errors or astigmatisms could cause pronounced discomfort after as little as half an hour at the computer. Properly fitted lenses could noticeably increase comfort.

Blinking hell

Otpometric experts now accept a reduced blink rate in screen workers can explain reports of dry or irritated eyes.

Dr James Sheedy, a clinical professor of optometry at the University of California at Berkeley, points to research showing that when people converse they blink, on average, 22 times a minute; when they read, they blink 10 times a minute, but when they use a VDU that drops to seven times a minute. He adds that people generally look down when they read but stare straight ahead at a screen so eyes are open wider and get dryer.

And Brian Keefe, Dollond and Aitchison's professional services director, says: "Concentrating on the screen can cause your blink rate to slow, which means that your natural tears are not able to lubricate your eyes as normal, leaving you with 'dry eye' symptoms."

The company has produced EyeSaver software, accessible on the internet, which automatically interrupts prolonged continuous work by reminding users to look away from their screen and relax their eye muscles. The web site also provides information on VDU safety laws (see Resources).

Other problems

People naturally try to look down at a computer screen at an angle of 10-20 degrees. Dr Sheedy warns that if the screen is at or above eye level, the tendency is to tilt the head back to achieve the desired viewing angle, and that can cause stiff necks and backaches.

People who wear bifocals or progressive (variable focus) lenses are forced to tilt their heads back to see the screen at all. Even with a head tilt, Sheedy says, the image is not as clear as it could be because the prescription typically issued for a reading lens is adjusted for an eye-to-page distance of 16 inches at an angle of 25 degrees, but computer screens are usually 20-24 inches away at an angle of 10-15 degrees.

Swedish researchers have found that screen flicker has been implicated in the development of electrical hypersensitivity, which can lead to symptoms including nausea, skin reddening, smarting or tingling, and aches, chills or fever.

Roger Wibom of Stockholm's National Institute for Working Life reported in September last year that during 1992 and 1993, 250 cases of electrical hypersensitivity were reported to the Swedish register for occupational illnesses, most of them due to computer work.

Safe at a glance

To work safety at a video display screen, check these points:

• Any windows should be at right angles to the computer screen, rather than behind it or in front of it;

• There should be enough light to read the words on the screen without straining;

• There should be no reflections on the screen from overhead lights, windows or desk lamps;

• The screen contrast should be adequate to produce sharply defined images.

Other factors, including rest breaks and office conditions - particularly humidity - can also be very important in the development of screen-related eye problems. The UK's Association of Optometrists recommends an office humidity level of 40-60 per cent.

Sight - the law

Regulation 5 of the Health and Safety (Display Screen Equipment) Regulations 1992 says "an employer shall ensure that a (user) is provided at his request with an appropriate eye and eyesight test." For those already employed, this can be "as soon as practicable after requested"; for new employees, it must be "before the employee becomes a user." Thereafter tests must be at "regular intervals".

Additionally, "where a user experiences visual difficulties which may reasonably be considered to be caused by work on DSE [display screen equipment], the employer shall ensure that he is provided on request" with a test.

The regulations also require that employers make their staff aware of their right to a free eye test. Risk assessments are legally required by the regulations and should fully assess all aspects of working conditions. They should be repeated periodically, or if there is a change in the work, working environment or the personnel doing the job.

Resources

Details of the Eyecare Vouchers scheme can be obtained from David Jenson, LV Group, 50 Vauxhall Bridge Road, London SW1V 2RS. Tel: 0171 887 1203.

Making VDU work safer, TUC guide. £5.00.

Your right to an eye test, TUC leaflet. Single copies free. Both from TUC Publications, Congress House, Great Russell Street, London WC1B 3LS.

Evaluation of the Display Screen Equipment Regulations 1992, HSE Contract Research Report No. 130/1997. ISBN 0 7176 1334 8. £37.50 from HSE Books, tel: 01787 881165.

Wibom R. Non-visual light modulation - A possible contribution to discomfort and hypersensitivity to electricity. OS 307. Book of Abstracts II. International Congress on Occupational Health, Stockholm 1996.