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A little light reading

Wednesday 17 September 2014

It has long been held that reading in poor light, whilst uncomfortable, cannot actually damage your eyesight. The most recent research would suggest otherwise.

As a recipient of thousands of marketing messages from various light bulb manufacturers every year, you would be forgiven for thinking that the various lighting technologies at our disposal have been around for many decades. The truth is that advances in lighting technology mirror many other technologies in terms of rates of development.

Thomas Edison’s pioneering work in the late 19th century on the development of carbon filaments provided the breakthrough that allowed mass production of incandescent bulbs, and by 1910 bulbs were being made with tungsten filaments. As far as domestic lighting is concerned, technology then virtually stood still for 90 years. Suddenly in the last decade, we have witnessed the rapid development of halogen lighting and the widespread introduction of the ‘energy saver’ or CFL bulb and, in more recent years, perhaps driven by imminent European legislation, LED technology has been accelerating at an even faster pace.

Have we seen the light?

But what has been the real impact of these technological changes? Some would say very little; in our homes and especially in our rooms of comfort the lighting we choose is invariably about the ambient effect it gives and the style of the light fitting rather than clarity of vision. The irony of this is that many thousands of people attempt tasks in the home with insufficient light, when the best lighting technology could make a huge difference to their visual acuity. All too often there is a passive acceptance of sight loss with little understanding of the dramatic difference good lighting can make.

For many people, the joy and importance of reading grows with age. Sadly for some, the challenge of reading may become too great if the health of their eyes becomes too compromised. For many others, the simple solution is a high quality light source to bring their vision and enjoyment of reading back to life. Whilst there is no substitute for a thorough eye examination, it is clear that a good light makes a dramatic difference. Although seemingly so obvious, sadly this fact is too often overlooked. What the eye needs year round for close tasks such as reading, writing, tapestry and many others, is high intensity localised light. In addition to the obvious benefit of improved visual clarity, it is widely accepted that better light improves a person’s well-being and quality of life especially during the winter months.

Bad light, damaged sight?

But can bad light actually damage the eye? It used to be commonly held that while reading in poor lighting might make us tired more quickly by having to strain to see, it didn't have a long-term detrimental impact on our eyes due to their adaptability and resilience. In 2007, the idea that reading in dim light ruins eyesight was named by researchers from the Indiana University School of Medicine as one of the “seven medical myths” that doctors are most likely to believe. The study, published in the British Medical Journal, revealed that reading in low light does not damage eyes, but rather causes eye strain.

Of course, eye strain is by no means a simple problem. If you read in low light, your visual muscles get mixed signals: relax to collect the most light, but at the same time, contract to maintain focus. When an object is poorly lit, focusing becomes even more difficult because contrast is reduced, which in turn decreases the eye’s ability to distinguish visual detail (visual acuity). In other words, your eyes have to work harder to separate the words from the page, which strains your eye muscles. When reading in poor light for a long period of time, they become tired, much as any muscle would. The strain may result in a number of physical effects including sore or itching eyeballs, headaches, back and neck aches and blurred vision.

Current research on poor light and myopia So, it is pretty clear-cut then – bad light doesn’t damage your eyes. Or does it? The latest research now puts this long-held assumption into question and suggests that concentrating in poor light might very well accelerate the onset of myopia. Recent studies have revealed that myopia is rife among Asian children. Reporting in the Lancet, researchers led by Ian Morgan of the Australian National University note that up to 90 per cent of young adults in major East Asian countries are nearsighted.

The researchers assert it is probably due to students’ spending too much time indoors studying and not enough time outside in the sunlight. It has long been thought that nearsightedness is mostly hereditary, but Dr Morgan says the data suggest that studying in poor light has much more to do with it.By contrast, the overall rate of myopia in the UK is about 20 to 30 per cent. So why the difference?

Myopia is the result of elongation of the eyeball, which leads to misalignment of light on the retina. Animal studies show that during early development, if the eye is not allowed to regulate its size to the proper length, then myopia can occur. The scientists think that the neurotransmitter dopamine may play a significant role in the structural development of the eyeball. Morgan believes that “bright outdoor light would stimulate the release of the retinal transmitter dopamine, which is known to be able to block the axial growth of the eye, which is the structural basis of myopia”.

Can the progression to myopia be averted? So far, no effective prevention methods or therapies exist other than corrective lenses. The drug atropine slows down eye growth, but the drops can cause side effects and they lose their effectiveness over time, says Morgan. “We need more evidence on just about everything that’s been tried,” he says. What the results do suggest is that hard-studying children might just benefit from a couple of hours of sunlight a day.

This theory is supported by independent research by a team led by Dr Justin Sherwin of the University of Cambridge. An analysis of eight previous Cambridge studies involving more than 10,000 children and adolescents revealed that short-sighted children spent on average 3.7 fewer hours per week outdoors than those who either had normal vision or were long-sighted. The team concluded that for each additional hour spent outside per week, the risk of myopia reduced by two per cent. Although the reasons why were not yet clear, the team assert that exposure to natural light and time spent looking at distant objects could be key factors.

Read in more comfort Irrespective of who wins the debate about the damage caused to eyes by poor light, it is the case that as one gets older the amount of light reaching the retina diminishes considerably and more light is needed to help one see things as clearly as one used to do. Even if your eyes are completely healthy, due to the natural ageing process, at age 60 they will require around three to four times as much light compared to a 20-year-old to achieve a comparable level of vision, whilst at age 40 they will already be likely to need twice the light they did when they were 20.

In poor lighting the visual system has to work harder, which often means a quicker onset of tiredness, thereby curtailing reading enjoyment. This is especially true if the reader has an eye condition such as cataracts or macular degeneration. Even in addition to prescription lenses if required, appropriate lighting has been shown time and again to reduce eyestrain and make a huge difference in comfort levels.

In short, the evidence on damage to the eye of operating in dim light may be unclear but the evidence of the impact of good light on the ability to see more clearly and with less strain is overwhelming.


  1. The Lancet:
  2. American Academy of Opthalmology:
    Children's Risk For Nearsightedness May Be Reduced By Spending More Time Outdoors .


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