Photophobia is a medical symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical sensitivity of the eyes, though the term is sometimes additionally applied to abnormal or irrational fear of light such as heliophobia. The term photophobia comes from the Greek φῶς (phōs), meaning "light", and φόβος (phóbos), meaning "fear".
Photophobia may manifest itself in an increased response to light starting at any step in the visual system, such as:
Common causes of photophobia include migraine headaches, TMJ, cataracts, Sjögren syndrome, mild traumatic brain injury (MTBI), or severe ophthalmologic diseases such as uveitis or corneal abrasion. A more extensive list follows:
Causes of photophobia relating directly to the eye itself include:
Neurological causes for photophobia include:
Treatment for light sensitivity addresses the underlying cause, whether it be an eye, nervous system or other cause. If the triggering factor or underlying cause can be identified and treated, photophobia may disappear. Tinted glasses are sometimes used.
People with photophobia may feel eye pain from even moderate levels of artificial light and avert their eyes from artificial light sources. Ambient levels of artificial light may also be intolerable to persons afflicted with photophobia such that they dim or remove the light source, or go into a dimmer lit room, such a one lit by refraction of light from outside the room. Alternatively, they may wear dark sunglasses, sunglasses designed to filter peripheral light, and/or wide-brimmed sun hats or baseball caps. Some types of photophobia may be helped with the use of precision tinted lenses which block the green-to-blue end of the light spectrum without blurring or impeding vision.
Other strategies for relieving photophobia include the use of tinted contact lenses and/or the use of prescription eye drops that constrict the pupil, thus reducing the amount of light entering the eye. Such strategies may be limited by the amount of light needed for proper vision under given conditions, however. Dilating drops may also help relieve eye pain from muscle spasms or seizures triggered by lighting/migraine, allowing a person to "ride out the migraine" in a dark or dim room. A paper by Stringham and Hammond, published in the Journal of Food Science, reviews studies of effects of consuming Lutein and Zeaxanthin on visual performance, and notes a decrease in sensitivity to glare.
Photophobia may preclude or limit a person from working in places where offensive lighting is virtually ubiquitous (e.g., big box stores, airports, libraries, hospitals, warehouses, offices, workshops, classrooms, supermarkets, and storage spaces), unless the person is able to obtain a reasonable accommodation like being allowed to wear tinted glasses when the employee dress code prohibits such glasses otherwise (which may be required to be provided by an employer under the Americans with Disabilities Act). Some people with photophobia may thereby be better able to work at night or be more easily accommodated in the workplace at night.
Outdoor night lighting may be equally offensive for persons with photophobia, however, given the wide variety of bright lighting used for illuminating residential, commercial and industrial areas, such as LED (light-emitting diode) lamps.
The increasing popularity of "overpoweringly intense" LED headlights being used on "pickups and S.U.V.s" has prompted more frequent reports of photophobia among motorists, cyclists, and pedestrians.