Futurology

It's actually a fairly common symptom of migraines, along with the pressure pain on one eye, since migraines itself are also usually on one side of the brain (the pain can spread though).

I think me suffering from migraines also makes me sensitive to certain light (flashes, specific colors like red light is really triggering, etc), somewhat similar to those with epilepsy, except that I don't end up with a seizure.