There are several causes of flashes. The most common cause is a posterior vitreous detachment (PVD), but a retinal tear, migraine and inflammation can also cause the same visual symptoms.
In other articles, a PVD and retinal tear have been well covered.
Flashes Due to Migraine
Without getting too specific, there are visual migraines that yield a scintillating light pattern, often confused with flashes. The array of lights lasts about 20 minutes and migrates across the field of vision. For instance, it may move from “right to left” over the 20 minute period.
This pattern generally resolves, or, there may be headache or other ocular symptoms that develop. These, too, last only for a finite period.
Any migraine, or symptoms that you feel are migraine related, should be evaluated by a doctor as there are other neurologic conditions that can give the same symptoms. This diagnosis, while seemingly benign, should be made as a diagnosis of exclusion, that is, make sure all other possibilities, such as tumor, are ruled out.
I often refer these types of cases to a neurologist or neuro-ophthalmologist to make sure I’m not missing something.
Flashes Related to Inflammation
Inflammation inside the eye is called uveitis, or iritis. It is very similar in nature to arthritis, another type of inflammation. Like arthritis of a joint, inflammation can occur just inside the eye.
Most commonly the inflammation is in the front of the eye, but on occasion, there can be types of inflammation affecting the retina. Symptoms can include flashes of light.
The best way to diagnosis retinal or retinal vascular inflammation is with a dilated eye exam. It is also probably prudent to seek the opinion of a retinal specialist in this case.
What Does This Mean?
In medicine, “everything has a differential.” In other words, in medicine, for a given symptom, it is a doctor’s responsibility to think of all the causes of a particular symptom.
For instance, flashes of light are often caused by a PVD or retinal tear, but could be caused by migraine or inflammation.