A recent article in the journal Headache explores the connection between photophobia and headache disorders.¹ It’s an overview intended for health care providers, but includes information that is helpful for patients, too. Here are some of the nuggets gleaned from the article:

• While “excessive or irrational fear of light” is the technical definition of photophobia, in medicine, it is used to refer to discomfort or pain caused by light.
• Photophobia can cause significant eye pain in some people.
• Light can also trigger or worsen head pain in people with migraine, tension-type headache, and cluster headache.
• The brightness of light that will be problematic for a person with a headache disorder is considerably lower than what bothers most people. In a study of people without headache disorders, light became uncomfortable when it reached 23,000 lux (equivalent to a bright, sunshiny day with no clouds in the sky)—and 24% of participants weren’t even bothered by that intensity of light. People with migraine reported discomfort between about 500 and 1,000 lux (“like an overcast day”). That's discomfort at as little as 2% the intensity of the general population.²
• During an attack, most people with migraine describe even low levels of light as glaring or painful. (In one study, every single participant reported sensitivity to light during an attack!²) People with migraine also report higher levels of photophobia between migraine attacks than those who do not have migraine.
• Tension-type and cluster headache also cause photophobia for most people, though studies suggest that the underlying mechanisms could be different for cluster headache than migraine and tension-type headache.
• People with tension-type headache are not as sensitive to light as someone is during a migraine attack, but they are more sensitive than people with migraine are between attacks.
• People with cluster headache have light sensitivity both during and between attacks, but only when they’re in a cluster.
• Photophobia occurs in both eyes, even when the headache is only on one side of the head.
• Applying ice to the foreheads of people with migraine increases photophobia, but does not cause light sensitivity in people without migraine.

The mechanisms of photophobia are not well understood. For headache disorders, in particular, scientists don’t know which mechanisms of photophobia are most relevant. Research on photophobia and headache disorders has increased in recent years, with recent studies pointing to a variety of possible physiological explanations. This knowledge is a key component to creating better treatments for all headache disorders.

REFERENCES

1. Rossi, H. L., & Recober, A. (2015). Photophobia in Primary Headaches. Headache: The Journal of Head and Face Pain.

2. Vanagaite, J., Pareja, J. A., Støren, O., White, L. R., Sand, T., & Stovner, L. J. (1997). Light-induced discomfort and pain in migraine.  Cephalalgia, 17(7), 733-741.