Many conditions cause photopsia, or flashes of light in the eye. Flashes of light can be harmless or an indicator of a serious eye problem that needs immediate treatment. Flashes accompanied by vision loss or by a large number of floaters, small specks that appear in your line of vision and appear to float or dart from side to side, should always be promptly reported to your eye doctor.
Migraines
Migraines, severe recurrent headaches caused by blood vessel spasms in the brain that last from a few hours to several days, often cause visual symptoms. Flashes of light that may look like zigzag lines, sparkles or geometric patterns often accompany migraines, the Massachusetts Eye and Ear Infirmary states. Flashes usually appear in the peripheral areas of vision and may affect one or both eyes. Light flashes can also occur without headache, a phenomenon called an ophthalmic migraine, All About Vision reports.
Posterior Vitreous Detachment
The vitreous, a gel-like substance that fills the center of the eye and gives it its shape, attaches to the retina. Over time, the vitreous shrinks and begins to detach in places from the retina, a condition called posterior vitreous detachment, or PVD. PVD affects as many as 75 percent of people over age 65, the Royal National Institute of Blind People reports. The vitreous pulls on the retina as it detaches, stimulating the retina and causing flashes of light to be seen.
No treatment for PVD exists, but regular eye examinations are done to watch for possible retinal detachment caused by the retina being pulled off the back of the eye as the vitreous tugs on it.
Retinal Detachment or Tear
Retinal detachment or retinal tears cause flashes of light that need prompt evaluation and treatment. Permanent vision loss can result if the retina detaches from the back of the eye, especially if detachment occurs over the macula, the central point of vision on the retina. The retina loses its source of nutrients when it detaches from the eye, and since the retina contains the photosensitive cells responsible for vision, the consequences from cell death can be severe.
Retinal detachment can occur after trauma or as a complication from PVD or diabetes, the Mayo Clinic states. Vitreous gel can seep under the retina through small tears or holes that occur from retinal thinning, raising up sections and disconnecting it from the eye, or a PVD can pull hard enough on the retina to pull parts of it away. Surgery, laser treatment or cryopexy, a freezing technique, all may be used to reattach the retina.
Other Causes
Trauma such as a blow to the head can cause a person to "see stars" or flashes of light. Digitalis toxicity can also cause flashes of light, All About Vision states. Digitalis is often taken to treat heart problems.
