Lee Ashdown was in the pub having a quiet drink after work when suddenly he looked over and couldn’t see half of his friend’s face. “I assumed I’d had too much to drink because I just felt completely disoriented.” He quickly made his excuses and left, going straight to bed when he arrived home.

But the distorted vision recurred and soon settled into a pattern. “It starts as a fuzzy line of light in the bottom corner of both eyes and works its way across my field of vision over an hour,” says the 37-year-old auditor from Heathfield, East Sussex. “Then it slowly disappears off into the top corners. That’s when the headache kicks in.”

A few months later, he went to see his GP, who told him that these were migraine auras. Migraines affect about 10% of the population in the UK, according to the National Migraine Centre. One in three of those people will experience auras. Confusingly for anyone who equates migraines with pain, sometime auras will appear without a headache; these are known as “silent migraines”.

Auras can be visual – normally coming in the form of flashing lights, zigzag patterns or blind spots – but they can also include other symptoms such as ringing in your ears, pins and needles, imaginary smells or aphasia, where a person temporarily loses the ability to speak or to understand others speaking.

Many sufferers worry that they are experiencing a transient ischaemic attack (TIA), also known as a mini-stroke. However, the symptoms of a migraine aura tend to be “positive” (such as flashing lights and skin tingling) and develop quite slowly, while those of a TIA are likely to be “negative” (losing the sensation in your hands or your vision in one eye, for example) and come on suddenly.

Zoe, 27, has been experiencing migraine auras since she was nine. “I get zigzag lines. It’s the same colours every time – very intense blues, pinks, yellows and black.” Each aura will last for two to four hours, with the intense headaches starting as they subside.

“I also get pins and needles, trouble speaking, loss of feeling in my hands and my legs … Sometimes it’s so bad, I’ve got no ability to even walk.” She also suffers from tinnitus during these attacks. “I get buzzing sounds like there are bees or wasps flying around my head.”

Zoe, who is a court administrator and lives in Leeds, has had problems at work because of the amount of time she has to take off, as she has up to 20 migraine auras a month. (An MRI has ruled out other causes.) They’ve also meant she has had to pull out of friends’ birthday parties at the last minute and miss out on important family events. “It just takes its toll, not being able to leave the house or do anything,” she says. “I was struggling with depression at one stage.”

Migraine auras are caused by something known as cortical spreading depression: a wave of electrical activity that moves across the cortex of the brain. Dr Mark Weatherall, a consultant neurologist at Stoke Mandeville hospital in Buckinghamshire and the chair of the British Association for the Study of Headache, compares it to “a little tsunami, a wave of overactivity followed by a trough of underactivity”.

These happen spontaneously, predominantly in the visual part of the brain, and are not harmful, he says. “As that wave spreads across the surface of the brain, each bit of the visual part of the brain is hit. The overactivity causes the flashing lights or the zigzags, and after that you get a period of underactivity, and that’s where you get the blind spots. Eventually that clears.”

READ RELATED: Weekend podcast: John Cho, anti-ambition, and naked yoga

For most people suffering from migraine auras, says Dr Weatherall, “all they need to do is rest and let them pass”. There are no treatments available for auras, only for the headaches. Mild pain can be managed with over-the-counter painkillers such as ibuprofen, paracetamol and aspirin. Research has shown that supplements such as magnesium and vitamin B2 can help prevent migraines, while coenzyme Q10 reduces the duration of an attack and ginger helps with pain and nausea.

For more severe attacks, triptans, anti-inflammatories and anti-sickness medication can be prescribed by your GP to manage any nausea and pain. Beta blockers, antidepressants and anti-seizure medication are also used to lessen the frequency of migraines.

Identifying personal triggers can be beneficial. Dr Dawn Sim, a consultant ophthalmic surgeon at Moorfields Eye hospital and the co-founder of the eye health brand MTHK, often has patients coming to see her with migraine auras, worried that there’s something wrong with their vision. After doing a thorough eye exam to exclude any other conditions, she then sits down with them to work out what their triggers are.

“Lack of sleep, caffeine, chocolate, tea, cheese and red wines … I reel these things off to people and they say: ‘Oh, so all the good things in life?’ You have to identify your trigger. If it’s excess consumption or any little piece of cheese that starts it off, in that case, you have to try excluding it from your diet. If it’s [auras] without headaches, it doesn’t tend to affect people’s lives.” For people who are suffering from debilitating migraines as well, she refers them to their GP or a neurologist.

“My food intolerances are pork and cheese,” says Kim Oliver, 50, from Liverpool, who is medically retired from her job as a clerical officer because of her migraines. She started experiencing migraine auras in 2006. “Bacon, sausage, paté – all my favourites – within 20 minutes of eating them, I’m out.”

A US study in 2007 of more than 1,200 people who suffered from acute migraines found that nearly 80% of participants considered stress a major factor. Other triggers included hormones in women, hunger, sleep disturbances, smells, neck pain, alcohol, smoking, heat, light, food, exercise and sexual activity.

Just over 53% also noted that the weather played a role, something that rings true for Oliver. “When it’s overcast and rainy, they’re my worst times,” she says. For Zoe, too, it seems to be the most consistent trigger. Her attacks can be set off if it’s “muggy or humid, or if it’s cold and then suddenly gets really hot”. Ashdown agrees: “The only thing I can think of that seems to correlate with getting these is when it’s quite stormy.”

Migraines, and particularly migraines with auras, are associated with a slightly higher risk of death from cardiovascular disease. But Dr Weatherall stresses there is no need for panic. “The vast majority of people who get migraines will have no consequences.” Equally, he says: “Nobody’s ever done a study that shows that if you reduce the frequency that people get migraines, then you reduce the risk of heart disease or stroke.”

As for Ashdown, he’s still praying for a cure, after almost 20 years of misery and countless tests to find out if there are any underlying issues. He has wasted too many days lying in a dark room waiting for the migraine auras to pass.

“I could make peace with them if I knew when they were going to happen. It’s the not knowing. I have to organise a stag do for my friend. If I’m out and I get one, what do I do? I’m hoping something comes out one day that can prevent them.”