Soon the clocks will go forward an hour and we'll all lose extra time in bed. However, the upside is that long sultry summer days are just around the corner. Fantastic! (You can't say I'm not an optimist.) However, being blind, apart from the hot sun against my face I won't detect any difference, as I can't distinguish between day and night.

It is estimated that 70% of totally blind people have a sleep disorder and as many as half of everyone with a significant sight loss could also be affected. It's because they can't tell light from dark.

I've discovered that I'm one of the unfortunate totally blind people who have trouble sleeping. It's like having permanent jetlag. There I am lying in bed, wide awake, at 4am, physically exhausted and wondering why I can't sleep.

It wasn't until I presented a radio programme that I discovered my poor sleep pattern had anything to do with my blindness.

The problem is caused by the disruption of the melatonin in the body. It controls the circadian rhythm, so we sleep at night and stay alert during daylight hours. The amount of light that reaches the eyes controls the quantity of melatonin that the pineal gland produces. Light slows down the production of the hormone. So, on a bright sunny day, you are alert and filled with energy. On a dull day, when the house is full of dark shadows, you become more lacklustre and sleepy. When evening falls and the lights go out, the pineal gland increases its production of melatonin. The hormone flows throughout the body and makes people sleepy. However, if you're blind, this doesn't work effectively and the body's natural rhythm becomes disrupted, throwing the sleep pattern out of kilter.

I've been visually impaired since birth, but because I had a little vision and the light was getting through to my pineal gland, my body was still excreting the melatonin hormone, so disturbed sleep patterns were not really an issue, until I lost all my sight a few years ago.

A blind friend had been complaining for years of not being able to get to sleep at night and he didn't understand why. Consequently, he would be shattered the following day at work, making it very difficult for him to function effectively. He also believed that his lack of sleep was much more disabling than his lack of vision.

Like him, if I've had a good night's sleep I can function quite normally. Moving around independently, operating my computer and interacting with my colleagues doesn't present any difficulty. But if I've not slept, it's quite a different matter.

It's very difficult to describe. Another blind friend who suffered badly from sleep deficiency explained it as having a squishy shield between you and the rest of the world. I know exactly what they meant. In this state of semi-wakefulness, combined with blindness, it can be extremely dangerous when moving around. It's so easy to get disoriented and misjudge stairs, traffic and other obstacles. Although it's largely incurable, the worst aspects can be significantly reduced by taking the drug melatonin before going to bed. Oddly, you would imagine that this would be commonly known, both among the blind community and the medical profession, but it's not.

Nearly three years ago I presented a documentary for Radio Scotland on this subject and was astonished how people were not aware of the problem. Many blind people I talked to admitted they had a sleep problem. However, few knew why and, even worse, when some went to their GPs to get help, hardly any doctors linked blindness to their sleeping difficulties. Melatonin doesn't work for everyone, though; some people can suffer from side-effects, such as headaches. So it's still worth getting medical advice, even if the GP is not fully aware of what you are talking about.

Over 24 hours, my body clock can slip by 30 minutes and over a six-week period, will do a complete 24-hour cycle with the added complication of no two days being the same However, if I take my melatonin every night before retiring, it can stabilise my sleep pattern. It's not only visually-impaired people who suffer from sleep disorders. Shift workers who do irregular hours can also be badly affected. Parents with small children can also find their circadian rhythm being thrown off balance by having to get up at irregular times during the night.

It is very difficult to get melatonin from your doctor here in the UK, as it's not on the list of approved drugs for prescription, though it is relatively easy to get it from the internet.

Sleep deprivation is only a problem because, as a blind person, I have to fit into a sighted world. If I didn't have to go to work at the same time every day or sit down to eat with everyone else, I could let my body clock fall into its own natural sleep pattern: breakfast at midnight, lunch at four in the morning and be home for dinner at around nine.

However, the reality is that I do have to fit in, so for that reason I will keep taking the pills.