What are flashes? Some people may see flashes of light in front of one of their eyes, like small sparkles, lightening or fireworks. These tend to be in the extreme corners of your vision, come and go, and don’t obscure any part of your vision. The flashes don’t last for a defined length of time, and you may notice them more if you go from a light to a dark environment. They may continue for several months. Flashes can occur when there is a pull on your retina. This might happen as the vitreous gel inside your eye becomes more liquid and collapses. You may experience flashes occasionally, on and off, over weeks or month. Flashes can also occur if you are hit in your eye. Flashes related to a collapse of the gel inside the eye are more likely to happen as you get older. Sometimes flashes just indicate a tug on your retina and nothing more. However, constant flashes may be a sign of retinal detachment. A retinal tear or a retinal detachment may lead to a sudden increase in floaters as well as flashes. You may notice a shadow at the edge of your vision too. This needs immediate attention. If you notice these symptoms, you should contact your optometrist straight away. If you cannot do this, you should get urgent attention from an eye casualty department at the hospital. If there is no eye casualty department nearby, you can go to your usual hospital casualty department, but it is best to go to an eye casualty department if you can. An ophthalmologist (a specialist eye doctor) will need to use eye drops and a special light to look inside your eyes to check if your retina is damaged. Flashes and migrainesFlashes are different to the shimmering or zig-zag lines that may be part of migraine. Migraine shimmers are a flickering of light, often only on one side of your vision with a sort of jagged pattern. This will often obscure at least part of your vision (the left or right side). The shimmers usually go away after 10-20 minutes and may be followed by a headache, although some people may get migraine shimmers even if they do not have a headache afterwards.