A 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.
Patients may develop photophobia as a result of several different medical conditions, related to the eye or the nervous system. In some cases those who are born with it see the full spectrum of light. While in the direct sun light it causes red glare around the visual field which causes pounding headaches. Photophobia can be caused by 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, cataracts, Mild Traumatic Brain Injury (MTBI), or severe ophthalmologic diseases such as uveitis or corneal abrasion.