Photophobia is a symptom of excessive sensitivity to light and the aversion to sunlight or well-lit places. In ordinary medical terms photophobia is not a morbid fear, but an experience of discomfort or pain to the eyes due to light exposure.
Light sensitivity is usually due to too much light entering the eye, which causes over stimulation of the photoreceptors in the retina and subsequent excessive electric impulses to the optic nerve. This leads to a reflex aversion to light, and discomfort or pain. Too much light can enter the eye if it is damaged, such as with corneal abrasion and retinal damage, or if a pupil(s) is unable to normally constrict (seen with damage to the oculomotor nerve).
Patients may develop photophobia as a result of several different medical conditions, related to the eye or the nervous system.
Causes of photophobia relating directly to the eye itself include:
- Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.
- Cone dystrophy
- Congenital abnormalities of the eye
- Viral conjunctivitis ("pink eye")
- Corneal abrasion
- Corneal dystrophy
- Corneal ulcer
- Disruption of the corneal epithelium, such as that caused by a corneal foreign body or keratitis
- Ectopia lentis
- Eye trauma caused by disease, injury, or infection such as chalazion, episcleritis, glaucoma, keratoconus, or optic nerve hypoplasia
- Hydrophthalmos, or congenital glaucoma
- Optic neuritis
- Pigment dispersion syndrome
- Pupillary dilation (naturally or chemically induced)
- Retinal detachment
- Scarring of the cornea or sclera
Neurological causes for photophobia include:
- Autism spectrum disorders
- Chiari malformation
- Subarachnoid haemorrhage
- Tumor of the posterior cranial fossa
- Ankylosing spondylitis – Causes Uveitis as an extra-articular feature.
- Benzodiazepines (long term use of or withdrawal from benzodiazepines)
- Chronic fatigue syndrome
- Ehlers-Danlos syndrome
- Infectious Mononucleosis
- Magnesium deficiency
- Mercury poisoning
- Tyrosinemia type II, also known as "Richner-Hanhart syndrome"
Patients with photophobia will avert their eyes from direct light (sunlight and room lights), or may seek the shelter of a dark room or wear sunglasses.