When most people hear the word "migraine," they think of a severely painful headache. However, there is a condition known as an ocular migraine that is related but painless. Rather than causing pain, it triggers visual hallucinations and problems. Ocular migraines are temporary and harmless, but they can be annoying. Although researchers haven't pinpointed the exact causes, there is evidence that certain factors play into triggering them.
Ocular migraines usually start out with a small flashing spot in the affected person's visual field. The spot will appear in one eye and gradually get worse, enlarging itself and taking on a distinctive zigzag pattern. Although there is usually no pain, it can impair the person's vision. It can last up to 30 minutes before disappearing on its own, although it usually ends within a few minutes.
Although the exact physical process that causes an ocular migraine is unknown, the Mayo Clinic says that the condition is probably triggered by a chemical or electrical wave. As it moves across the visual cortex, which processes visual signals, it can trigger hallucinations like the flashing, zigzag lights. Once the wave passes, so do the hallucinations. Marilyn Haddrill of All About Vision says that obstructed blood flow in the brain may also play a role.
The Mayo Clinic's Dr. Dennis Robertson says that the exact causes of ocular migraines are unknown, but certain foods may be triggers. He says they may be caused by such diverse foods as chocolate, shellfish and nuts. Unlike a food allergy, these dietary items may not trigger an ocular migraine every time they are consumed so it can be difficult to establish a link.
Dr, Robertson says there may be a link between ocular migraines, alcohol and caffeine. Beverages containing alcohol and caffeine can have a dehydrating effect, and dehydration is also considered a possible ocular migraine cause. This makes it difficult to tell whether the substances themselves are the culprits or whether they trigger the problem by dehydrating a person.
Artificial sweeteners such as aspartame, which goes by the brand name Nutrasweet, may be an ocular migraine trigger. Eating foods or drinking beverages that contain these sweeteners may increase the chance of having an ocular migraine. The Mayo Clinic says there might also be a link between this condition and food preservatives.
There is some anecdotal evidence that stress and fatigue may make a person more susceptible to ocular migraines. However, Dr. Robertson says that researchers have not been able to establish a definitive link. A person's emotional state may combine with the other factors to make them more vulnerable to an ocular migraine.