Summary
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". Patients may develop photophobia as a result of several different medical conditions, related to the eye, the nervous system, genetic, or other causes. Photophobia may manifest itself in an increased response to light starting at any step in the visual system, such as: Too much light entering the eye. Too much light can enter the eye if it is damaged, such as with corneal abrasion and retinal damage, or if its pupil(s) is unable to normally constrict (seen with damage to the oculomotor nerve). Due to albinism, the lack of pigment in the colored part of the eyes (irises) makes them somewhat translucent. This means that the irises can't completely block light from entering the eye. Overstimulation of the photoreceptors in the retina Excessive electric impulses to the optic nerve Excessive response in the central nervous system 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: Achromatopsia Aniridia Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.
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