Flashes of light in the eyes can be attributed to various factors. One common cause is the shrinking and pulling of the vitreous, the clear, gel-like substance in the eye's center, which can trigger these light sensations. Such flashes may come and go over several weeks or even months. As people age, experiencing these flashes becomes more frequent, though they typically aren't indicative of a serious issue. However, if you suddenly start seeing flashes or notice an increase in their frequency, it's important to consult an ophthalmologist to check for potential retinal tears or other causes. Flashes resembling jagged lines or "heat waves" that last 10-20 minutes in both eyes are usually the result of a spasm of blood vessels in the brain. These can happen without an accompanying headache, in which case they are referred to as migraine without headache.