Putting an end to old fashioned flickering

In the mid-1950s, schools began to introduce fluorescent lighting. Rows of these low cost, long life, high efficacy lamps tend to be the lighting of choice in many schools around the world.

But some fluorescent lighting could actually be causing eye strain and headaches. Why? Many, but not all, fluorescent tubes vary in colour and brightness continually because the light of fluorescent bulbs is produced by a gas discharge (like lightning) twice, with each cycle of the alternating current.

A 2009 survey found that 80% of classrooms were still lit with the old-fashioned flickering fluorescent lighting

The variation in colour comes about because ultraviolet light from the discharge is converted to visible light by a coating of phosphor on the inside of the lamp and this continues to glow between flashes. The resulting coloured flicker is too rapid to be seen, but it results in an electrical signal from the back of the eye, indicating that our cells respond to the variation.

This rapid fluctuation of light from fluorescent lamps is known to affect the way our eyes move across text and it interferes with the performance of visual tasks. And while it does not affect everybody, it can have a serious effect on a few. Indeed, one study found incidences of headaches and eye strain in a London office halved when the fluorescent flicker was reduced.

Fluorescent lighting installed in the last 10 years does not usually flicker in this way. But a 2009 survey found that 80% of classrooms were still lit with the old-fashioned flickering fluorescent lighting.

Some children see an improvement in the clarity of text when a sheet of coloured plastic – a coloured overlay – is placed on the page. Children who use coloured overlays find they are able to read more quickly – and often report a reduction in eye-strain and headaches.

One possible reason is that a coloured filter can reduce the variation in colour that occurs with the old-fashioned fluorescent lighting.

If you have to spend a lot of time under fluorescent light, make sure fluorescent lamps are controlled by high-frequency electronic circuitry.

Some colours will be more suitable than others at reducing any effects of the rapid variation in colour and brightness from fluorescent lights, depending on the phosphors in the lamps, and how much the children have experienced the flicker and adapted to it.

Of course, fluorescent lighting isn’t just found in schools and the impact isn’t just something that affects children. Many offices are filled with tube lighting and it’s known there’s a link between fluorescent lighting and migraines, too.

Clearly it would be preferable for schools and workplaces to replace the old-fashioned fluorescent lighting with newer electronic circuitry that removes the 100-per-second variation. This would not only be healthier for children and teachers but also reduce the running costs. This is particularly important given that one in five children in England cannot read well by the age of 11 – and it may be that for at least some of these children, fluorescent lighting could be part of the problem.

Read the AOP guidance for parents on children’s eye health.

A version of this article was published in online research publication The Conversation in November 2019.

Arnold Wilkins is a professor at the University of Essex and designed the Intuitive Colorimeter.

Image credit: Getty/mathisworks