Sunlight can affect headaches in two completely different ways. Too much sunlight produces glare, while in certain people too little produces a condition called Seasonal Affective Disorder.


Brilliant sunlight causes glare. We respond to glare by tightly screwing up our feces in order to minimise the amount of light coming into our eyes. Over a short period of time, glare does no damage (provided you’re not looking directly into the sun), but over a longer period, screwing up the muscles around the eyes I Buses tension headaches. The longer the glare continues the more likely it is to cause headaches

Glare is essentially too much unwanted light, but it doesn’t have to be a very sunny day to cause glare; the direction of light counts, as well. It’s unwanted light coming into your eyes that determines whether glare is present; it’s quite possible to have a sunny day in a Mediterranean country, with the sun at its zenith, and have little glare. On the other hand, you can experience glare by driving straight into the sun at three o’clock on a December afternoon in Manchester!

So what is it about light that makes it glare? The answer is two fold. Obviously the more light there is the more likely it is that glare will occur. However, a lot of sunlight falling on a landscape that is primarily dark won’t cause much glare. It’s the bounce-round of light reflecting on light surfaces that causes the difficulty; i.e., light coming off snow, off sand, off water, off light-coloured surfaces such as concrete paths and buildings, reflecting off windows, off the white pages of a book or newspaper, and off white garden furniture and walls. And anything that reflects sunlight as brilliant flashes of light makes glare even worse.

However, direct, intense sunlight isn’t always necessary. A lot of glare is created when the sun is behind a thin haze of high cloud. This makes the whole sky radiate light, instead of it coming just from the sun. If you’ve ever been to an air show under these conditions, you’ll know how much more wearing it is to look at aircraft against a bright white background like this, than it is to watch the Red Arrows against the backdrop of a deep blue sky.

What can you do about glare? The answer is quite simple – minimise the amount of reflected light coming into your eyes. For instance, if eating outside minimise glare by using a dark-coloured tablecloth and using pottery cups and saucers, rather than glasses or china which reflect light so much more. Putting up a parasol helps as well! And, if you have a particularly bright area in the garden (perhaps a patio with a white, concrete floor), avoid it during the brighter times of the day.

Sunglasses are very effective. Simply donning a pair of tinted spectacles may make all the difference and it certainly allows you to read a book more comfortably. Polarised sunglasses are particularly useful; they have a material within them which only allows light to pass through if it is vibrating at a particular angle. Basically this means that they can selectively cut out glare and reflected light, instead of just light in general. Tinted glasses simply reduce the total amount of light, which is of some benefit, but not as effective as polarised lenses.

Seasonal Affective Disorder (SAD)

Seasonal Affective Disorder (or SAD, for short) is a recently discovered cause of. depression which is primarily related to a lack of sunlight. Sufferers from SAD find that they become lethargic and depressed around October. This feeling lasts until about April, when suddenly they get a burst of activity, their depression lifts and they feel normal again … until the following autumn. SAD is now a well-recognised cause of depression, which can cause muscle tension and headaches.

Only a small proportion of people seem to be susceptible to SAD, which seems to be related entirely to the amount of light coming into the eyes. So, if you work outdoors, you’re less likely to be affected, while if you work inside you could be afflicted that much more quickly.

The treatment, as you’d expect, is exposure to light; but the intensity of light is very important. Normal levels of artificial light, even in brightly lit surroundings, are simply not enough. In other words, what we feel is powerful artificial light is, by comparison with sunlight, very weak indeed.

There are special lights available to treat sufferers of SAD; these are called ‘light boxes’ and are of particularly high intensity. It isn’t necessary to look straight at the box, as long as you have it in your field of vision. You could read, or watch television at the same time, for example.

What do you do if you are suffering from SAD? To begin with, make the most of any natural light you can, especially towards autumn and winter. Ensure that you have an outdoor hobby – walking, golfing, gardening – and make a point of going out in the sunlight whenever you can. Perhaps you could have your mid-day meal on a bench in the park rather than merely sitting in the office. Secondly, think about a winter holiday somewhere much sunnier, where there are longer periods of daylight, or a lot of snow (snow will tend to multiply the effects of daylight by producing a lot of glare).

Lastly, in cases where SAD has been diagnosed, your doctor can arrange light therapy in which you are exposed to artificial light of a sufficiently high intensity to counteract the effects of lack of natural sunlight.


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