Photophobia

Photophobia is a symptom of abnormal intolerance to visual perception of light.^[1] 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,^[2] though the term is sometimes additionally applied to abnormal or irrational fear of light such as heliophobia.^[3] The term photophobia comes from the Greek φῶς (phōs), meaning "light", and φόβος (phobos), meaning "fear".^[4][5]

Causes

Patients may develop photophobia as a result of several different medical conditions, related to the eye or the nervous system. 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
• Elevated trigeminal nerve tone (as it is sensory nerve to eye, elevated tone makes it over reactive). Elevated trigeminal tone causes elevated substance P which causes hypersensitivity. Often due to jaw misalignment.^[6]

Common causes of photophobia include migraine headaches, TMJ, cataracts, Sjogren's Syndrome, Mild Traumatic Brain Injury (MTBI), or severe ophthalmologic diseases such as uveitis or corneal abrasion.^[7] A more extensive list follows:

Eye-related

Causes of photophobia relating directly to the eye itself include:

• Achromatopsia^[8]
• Aniridia^[9]
• Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.
• Aphakia^[10] (absence of the lens of the eye)
• Blepharitis
• Buphthalmos^[9] (abnormally narrow angle between the cornea and iris)
• Cataracts^[9]
• Coloboma
• Cone dystrophy^[9]
• Congenital abnormalities of the eye^[9]
• Viral conjunctivitis ("pink eye")^[11]
• Corneal abrasion^[9]
• Corneal dystrophy^[9]
• Corneal ulcer^[12]
• Disruption of the corneal epithelium, such as that caused by a corneal foreign body or keratitis^[9]
• Ectopia lentis^[9]
• Endophthalmitis^[9]
• Eye trauma caused by disease, injury, or infection such as chalazion, episcleritis, glaucoma,^[9] keratoconus, or optic nerve hypoplasia
• Hydrophthalmos, or congenital glaucoma^[9]
• Iritis^[9]
• Optic neuritis^[9]
• Pigment dispersion syndrome
• Pupillary dilation (naturally or chemically induced)^[10]
• Retinal detachment
• Scarring of the cornea or sclera^[9]
• Uveitis^[9]

Nervous-system-related

Neurological causes for photophobia include:

• Autism spectrum disorders^[13]
• Chiari malformation
• Occipital Neuralgia
• Dyslexia^[14]
• Encephalitis^[9] including Myalgic encephalomyelitis aka Chronic fatigue syndrome^[15]
• Meningitis^[9]
• Trigeminal disturbance causes central sensitization (hence, multiple other associated hypersensitivities. Causes can be bad bite, infected tooth, etc.^[16]
• Subarachnoid haemorrhage^[17]
• Tumor of the posterior cranial fossa^[9]

Other causes

• Ankylosing spondylitis^[18] — Causes Uveitis as an extra-articular feature.
• Albinism^[19]
• Ariboflavinosis^[20]
• Benzodiazepines (long-term use of or withdrawal from benzodiazepines)^[21][22]
• Chemotherapy^[9]
• Chikungunya^[23]
• Cystinosis^[9]
• Drug withdrawal
• Ehlers-Danlos syndrome^[24]
• Infectious mononucleosis (Glandular Fever)^[25][26]
• Influenza^[27]
• Magnesium deficiency^[28]
• Mercury poisoning^[29]
• Migraine^[30]
• Rabies^[31]
• Tyrosinemia type II, also known as "Richner-Hanhart syndrome"^[9]
• snake bite
• Lyme disease

Treatment

The best treatment for light sensitivity is to address the underlying cause. Once the triggering factor is treated, photophobia disappears in many but not all cases.^[32]

People with photophobia will avert their eyes from direct light, such as sunlight and room lights. They may seek the shelter of a dark room. They may wear sunglasses designed to filter peripheral light and wide-brimmed sun hats.

Wearing sunglasses indoors can make symptoms worse over time as it will dark-adapt the retina which aggravates sensitivity to light. Indoor photophobia symptoms may be relieved with the use of precision tinted lenses (e.g. FL-41) which block the green-to-blue end of the light spectrum without blurring or impeding vision.^[33][34]

A paper by Stringham and Hammond, published in the Journal of Food Science, reviews studies of effects of consuming Lutein and Zeaxanthin on visual performance, and notes a decrease in sensitivity to glare.^[35]

Effects

Photophobia may also affect patients' socioeconomic status by limiting their career choices, since many workplaces require bright lights for safety or to accommodate the work being done. Sufferers may be shut out of a wide range of both skilled and unskilled jobs, such as in warehouses, offices, workshops, classrooms, supermarkets and storage spaces.^[36] Some photophobes are only able to work night shifts, which reduces their prospects for finding work.^[37]

See also

• Photic sneeze reflex, a medical condition by which people exposed to bright light sneeze
• Photosensitivity in humans

References

External links

• AllAboutVision.com page on photophobia
• WrongDiagnosis.com page on photophobia