Photophobia

Overview
Photophobia (also light sensitivity) or fear of light, is a symptom of excessive sensitivity to light and the aversion to sunlight or well-lit places. In medical terms, it is not fear, but an experience of discomfort or pain to the eyes due to light exposure.

Pathophysiology
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).

Differential diagnosis of causes of photophobia
Patients may develop photophobia as a result of several different medical conditions, related to the eye or the nervous system.


 * Meningitis
 * Eye disease, injury, or infection such as chalazion, episcleritis, glaucoma, keratoconus
 * Subarachnoid haemorrhage
 * Albinism
 * Burns to the eye
 * Migraines
 * Encephalitis
 * Conjunctivitis
 * Aphakia
 * Iritis
 * Corneal abrasion
 * Corneal ulcer
 * Cataracts
 * Retinal detachment
 * Chiari malformation
 * Cystinosis
 * Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.
 * Hangover
 * Chikungunya
 * Conjunctivitis
 * Encephalitis
 * Idiopathic anterior uveitis/iritis
 * Influenza
 * Keraconjunctivitis sicca (dry eye)
 * Lightly pigmented eye
 * Meningitis
 * Migrane
 * Mydriatic use
 * Subarachnoid hemorrhage

Signs and symptoms
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.

Photophobia is also a behavior demonstrated by insects or other animals which seek to stay out of the light.