Dr Martin Scurr provides information on retinal migraine, its symptoms, diagnosis, and treatment. He also addresses concerns about excessive vitamin C intake.
Dr Martin Scurr replies: For readers unfamiliar with the condition, let me first explain that retinal migraine is different from standard migraine with aura. Both involve visual disturbances, but migraine with aura affects both eyes, while retinal migraine – which is much less common – affects only one.
Symptoms include a dimming of vision in that eye lasting from five minutes to an hour, followed by a full recovery of vision, then a headache. Retinal migraines are caused by a spasm in the blood supply to the retina (the area of nerve tissue at the back of the eye that converts light into signals that the brain processes as vision). Given that your episodes have recently increased in frequency, it’s important to have your diagnosis re-confirmed.
Retinal migraine is a diagnosis of exclusion – meaning that other conditions need to be ruled out first. I assume this happened at your original diagnosis, but it is important to be sure.
In particular, a condition called amaurosis fugax should be ruled out – this involves brief, recurrent episodes of visual disturbance caused by tiny clots. So I would suggest seeing your GP promptly.
Retinal migraine is a diagnosis of exclusion – meaning that other conditions need to be ruled out first If retinal migraine is confirmed, the first-line preventative treatment is drugs that reduce spasms of the blood vessels in the retina – for example, calcium channel blockers, such as nifedipine, which are used for hypertension and angina. Other options include drugs used to prevent migraine – such as propranolol, topiramate and amitriptyline; these aren’t migraine drugs but are used because they act on the neurological mechanisms involved.
I am a healthy, active 78-year-old woman with two knee replacements and one hip replacement. I have always taken supplements, including cod liver and evening primrose. But I worry that I may be getting too much vitamin C – 725mg a day from supplements and food. Might this harm me?
Angela Bunker, Milton Keynes. Dr Martin Scurr replies: The accepted advice used to be not to worry about any potential harmful effects from larger doses of vitamin C – the NHS currently recommends a daily intake of 40mg – on the grounds the vitamin is water soluble so any excess would be passed out in your urine. But while this is mostly true, it’s not the whole story.
Remarkably little is known about the toxicity of many vitamins and minerals, according to The Manual of Dietetic Practice – widely regarded as the textbook on dietary matters. But we do know that very high doses of vitamin C (more than 1,000mg a day) can cause problems, such as abdominal pain or diarrhoea. This is because it irritates the gut lining, causing it to draw water into the intestines which in turn leads to cramping, bloating and loose stools.
One daily orange alone provides 80-100mg of vitamin C, which is more than double your daily recommended amount There’s also evidence that very high doses (several grams a day) can increase the risk of kidney stones, as vitamin C is broken down into oxalate: high levels of oxalate in urine can lead to calcium oxalate stones, the most common type of kidney stone. High vitamin C levels can also cause problems for people with certain conditions, such as haemochromatosis – where the body absorbs too much iron – because it boosts iron absorption, causing potentially seriously toxic levels.
It’s clear from your longer letter that you are already getting plentiful vitamin C from your diet alone. In fact your daily orange alone provides 80-100mg, which is more than double your daily recommended amount. I therefore suggest you drop the daily 500mg vitamin C tablet – your body doesn’t need it
Retinal Migraine Diagnosis Treatment Symptoms Diagnosis Of Exclusion Amarourosis Fugax Preventive Treatment Drugs Vitamin C Intake Harmful Effects
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