A flash in your vision indicates that your brain has interpreted an improper stimulation of your retina or optic nerve as light. The actual sensation varies from person to person, with some seeing an arc of light and others likening it to a light-bulb switching on and off rapidly. Flashes can result from a wide range of causes, from sudden eye movements to severe conditions such as retinal damage.
Retinal Tears or Retinal Detachment
If the flashing occurs in only one eye, it may be due to a retinal tear or detachment, in which case you must schedule an examination as soon as possible. Though uncommon, torn retinas and retinal detachments are the most severe cause of flashes or streaks of light in your vision, and must be ruled out as soon as possible. If untreated, they may result in a significant loss of vision in the affected eye. Torn retinas may only require laser treatment, but a retinal detachment requires surgery.
A more probable cause of momentary light flashes is vitreous detachment, especially if you are nearsighted, have experienced eye inflammation, or have gone through a cataract operation. Having a family history of retinal detachment also increases the probability of vitreous detachment. Vitreous detachment happens when the eye's clear internal gel thickens or shrinks, causing it to separate from the retina. It doesn't require any treatment and is actually a common occurrence among aging people. Nevertheless, patients who experience vitreous detachment still should watch for signs of retinal tears.
Migraines are another common cause of flashes and result from a reduction of blood flow to the brain. Migraines are characterized by a constriction of arteries in the brain, followed by their dilation. These changes often result in sensory disturbances, such as light flashes, which may or may not be followed by a headache. These flashes of light tend to last longer than flashes caused by vitreous detachment -- often 10 to 20 minutes -- and may even have recognizable shapes and colors.
Other Possible Causes
Light flashes may also have a number of other causes. A blow to the head can result in flashes, either by causing a retinal tear or by accidentally stimulating the brain's occipital lobe. Blood flow changes from sudden movements can also cause flashes. In some patients, flashing lights are linked to eye conditions, such as retinal artery occlusion and glaucoma, and in other cases are even indicative of hypertension, diabetes and potentially even multiple sclerosis.
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