Flashing Lights. Sometimes I see unexplained flashing lights. This occurs at night when my eyes are closed. What could cause these episodes? They are like a strobe light. I investigate, with research, medical causes of unexpected flashing lights.
Seizures. Simple partial seizures involve no loss of consciousness. If you have a seizure in your occipital lobes, you will get vision changes. Nystagmus is an uncontrollable movement of the eyes. It is one possible symptom.

And:Blinking, or flashing lights (or colored lights) are also possible in a simple partial seizure.

Foci in the occipital lobes produce nystagmus, blinking, or visual disturbances, such as flashing lights or the appearance of strange colors.

Foye's Principles of Medicinal Chemistry
Complex partial seizure. The symptom of flashing lights is also possible in a complex partial seizure. In a complex seizure, however, consciousness (or mental state) is impaired. You might not remember seeing the flashing lights.
In my research, I saw case studies of flashing lights (as from TV). Sometimes the EEG tests provide no evidence of abnormal brain activity. So a diagnosis must be made on symptoms alone. This turns a diagnosis into more of an opinion.

Caution:In some patients, a simple partial becomes a generalized seizure. This means a tonic-clonic seizure. A person loses consciousness.

Seizure trigger. Flashing lights are not just a symptom of epilepsy. They can also trigger a seizure in someone who has epilepsy. They are both a symptom, and a cause. In an EEG, flashing lights are used to provoke brain wave changes.

While high-intensity strobe lights like those used during EEG may precipitate seizures, they are uncommonly encountered outside of nightclubs and theaters.

Alternative Therapies For Epilepsy
According to the book Alternative Therapies For Epilepsy, photosensitivity is fairly common. About 3% of people (mainly women and children) have abnormal brain waves because of flashing lights. Seizures from lights, however, are rare.

And:Seizures precipitated by lights or flashes are found in only 1 out of 10,000 people in the general population.

Old age, retina. As we become older, it is normal to start seeing lights or even lightning-like flashes. This is because of wear and tear on the retina and the vitreous gel in the eyes. In the book The Aging Eye, we learn more about this problem.

Seeing shooting stars—a phenomenon called photopsia—is not unusual as people age. Solitary flashes appear as sparks or minuscule strands of light, almost like streaks of lightning...

The Aging Eye: Preventing and treating eye disease
Many of these symptoms are harmless, but we must be certain that a more serious problem is not present. A retinal tear or detachment may be behind some of these symptoms, but usually is not. An ophthalmologist can diagnose the problem.

They occur when the vitreous gel bumps, rubs, or tugs against the retina. Generally harmless, they require no treatment. In rare cases, they may be a sign of more severe retinal complications.The Aging Eye

Not migraine. Finally, the flashes in retinal problems is different from that of migraines. In migraine headaches, the flashes will last many minutes or even hours. And in migraine, the flashes occur in both eyes.

Note:Thanks to the authors of The Aging Eye: Preventing and Treating Eye Disease. This is a textbook from Harvard.

Phototopsia differs from the flashing or zigzag lights that may precede migraine headache, which some people experience simulataneously in both eyes, typically for as long as 20 minutes.The Aging Eye

Migraine. Do you suffer from headaches? A migraine headache is not the same as a tension headache: it often has an aura. In a migraine aura, visual symptoms may occur. In fact, in 99% of migraine auras, visual signs predominate.

Tip:In the book Migraine in Women, we learn more about the nature of these visual symptoms. Flashing is in the periphery of your vision.

Ninety-nine percent of auras are visual... flashing lights in peripheral visual fields (photopsia), wavy or zigzag lines (fortification spectra), slowly enlarging blind spots, frequently edged with shimmering lines.

Migraine in Women
As with epileptic seizures, migraines have auras. And migraines may also be triggered by flashing lights. So for migraines, as well as epilepsy, flashing lights are a trigger as well as a symptom. Avoiding flashes is a safe option.

Also:Treatments for migraine headaches have some overlap with treatment for epileptic seizures.

Therefore:An exact diagnosis (epilepsy or migraines) may not always be important. The same treatment could symptoms in either case.

Story. Sometimes in the dark, I experience flashing in my vision, even with my eyes shut. The effect is the same as in a lightning storm, except I am usually in bed. And my eyes are always shut. This usually lasts for only 5 or 10 seconds.
I have had some complicated medical problems in the past. And I have seen a neurologist, a neurosurgeon as well as an ophthalmologist. For me, my symptoms most resemble a form of seizure associated with optic nerve.

So:Flashing lights, like I describe here, are sometimes the result of a brain lesion. They are in my case.

However:Fortunately in my case, the problem is not severe and it does not impede my life in a significant way.

If you have flashing lights in your vision, I recommend a neurological consult. More often than not, some sort of problem will be found. If the symptom is recurrent, and you are concerned about it, there is likely some problem.

And:It might be a problem with your eyes or your brain. A migraine aura, or a seizure might be responsible.

Tip:As I found, sometimes these issues are not easy to diagnose. So two doctors might disagree on a proper diagnosis.

Summary. Flashing lights in your vision can be caused by many disorders. Brain conditions, like epilepsy or migraine, are possible. For older people, retina issues are more common. If the problem is alarming or severe, the problem may be emergent.

And:For an emergent problem, a visit to your local emergency department may be required.