American researchers have released test results that could help ophthalmologists better understand why certain patients struggle with light sensitivity (aka photophobia).
Researchers at the University of Pennsylvania took a group of patients with photophobia and examined how their pupils responded to a bright pulse of light. The light pulses used in this study were specifically designed to stimulate an eye protein known as melanopsin.
What the investigators found was that the light stimulated not only melanopsin cells, but also the visual pathway leading up to the brain. The light used in this study wasn't designed to move into a person's normal field of vision. From this data, researchers believe melanopsin malfunction may be a root cause of photophobia.
As mentioned above, melanopsin is a protein inside the eye that's extremely sensitive to blue light. In addition to tightening the pupils when exposed to bright light, melanopsin is important in regulating our sleep cycle.
Most of the photophobia patients examined struggled with migraines, eye diseases, or had recently suffered a concussion. Almost every patient who participated in this study said they felt intense discomfort when doctors turned on the light in their eyes.
Although there is "phobia" in the name, photophobia doesn't refer to a fear of lights. Instead, photophobia is a condition in which people experience eye pain or headaches due to light sensitivity.
Photophobia isn't considered an eye disease in and of itself, but rather is a symptom of other conditions. Many people who suffer from photophobia have light color pigmentation in their eyes, colorblindness, frequent migraines, and/or viral infections. Also, certain medications can trigger this condition.
A few things people with photophobia can do to protect themselves from the sunlight include wearing hats, investing in polarized sunglasses, and, in more extreme cases, trying out prosthetic contact lenses.
The lead study authors on this test include Drs. Manuel Spitschan, Andrew S. Bock, and David H. Brainard.
Anyone interested in reading this full study should pick up the latest edition of the Proceedings of the National Academy of Sciences. This article is listed under the title, "The human visual cortex response to melanopsin-directed stimulation is accompanied by a distinct perceptual experience."