Photophobia

Photophobia, also known as light sensitivity, is a symptom of abnormal visual intolerance to light. It can manifest as discomfort or pain. It occurs in ME/CFS as part of a range of sensitivities such as allodynia, hyperacusis and misophonia. Photophobia also forms part of the wide range of ocular symptoms that occur in ME/CFS.

Prevalence
70.7% - 75.8% of the 2073 patients in a Belgian study of 2001 reported having photophobia.

Symptom recognition
Photophobia is not a symptom required for diagnosis in any definition. In the Canadian Consensus Criteria, it appears under the section Neurological/Cognitive Manifestations and can be used to form a diagnosis. The International Consensus Criteria also lists photophobia as a diagnostic criteria, under the section Neurosensory, perceptual and motor disturbances. It also appears in the Holmes criteria, where it comes under the minor criteria Neuropsychologic complaints.

No other definitions mention photophobia.

Notable studies
There have been no studies done specifically on photophobia in ME/CFS.

Possible causes
Photophobia can be caused by the pupil dilating rather than contracting when exposed to a light source. Pupil dilation is controlled by the sympathetic nervous system, which is usually hyper-responsive in people with ME/CFS due to an excess of excitatory neurotransmitters.

A magnesium deficiency can cause photophobia, and such deficiency is common in ME/CFS. This can be resolved with appropriate magnesium supplementation.

Some medications have photophobia listed as a side effect, notably benzodiazepines.

Photophobia is also often caused by illnesses that are common comorbidities of ME/CFS, such as Sjögren's syndrome, TMJ, migraines, Ehlers-Danlos syndrome, infectious mononucleosis, chiari malformation, dyslexia and lyme disease.

Learn more

 * Wikipedia - Photophobia
 * Shedding Light on Photophobia