Photophobia

Photophobia is discomfort or pain from light, with a wish to avoid bright light. It indicates ocular surface or intraocular inflammation, neurological disease (migraine, meningitis, subarachnoid haemorrhage, raised intracranial pressure), or functional hypersensitivity.

Mechanisms. Light stimulates intrinsically photosensitive retinal ganglion cells that project to the trigeminal and thalamic pain pathways. Corneal and ciliary muscle inflammation sensitises trigeminal afferents, and spasm of the iris sphincter and ciliary body causes pain.

Classification. Ocular (corneal, anterior chamber, iris, lens, retinal), neurological (migraine, meningitis, subarachnoid haemorrhage, raised intracranial pressure, post-concussion, blepharospasm, thalamic lesions, trigeminal), systemic and drug related (botulism, albinism, drugs), and psychiatric.

Key distinctions. Photophobia with a red eye and pain indicates keratitis or uveitis. Photophobia with headache and neck stiffness indicates meningitis or subarachnoid haemorrhage. Photophobia with a quiet white eye and migraine history indicates migraine.

History. Ask about:

• Onset, duration, severity, and which eye
• Pain, redness, tearing, discharge, vision change
• Contact lens use, trauma, ultraviolet or welding exposure, recent eye surgery
• Headache, nausea, aura, fever, neck stiffness, rash, head injury, concussion, neurological symptoms
• Dry eye
• Systemic illness (inflammatory bowel disease, ankylosing spondylitis, sarcoidosis, Behcet disease, juvenile idiopathic arthritis)
• Medication, and migraine history

Drug history. Drugs causing mydriasis (anticholinergics, antihistamines, tricyclic antidepressants, sympathomimetics, atropine drops), doxycycline and other photosensitising drugs, belladonna, benzodiazepine withdrawal, quinine, chloroquine, and cannabis.

Examination. Check visual acuity, pupils (size, shape, reaction), conjunctiva (ciliary flush), cornea (staining with fluorescein, infiltrate, dendrite), anterior chamber (cells and flare, hypopyon), intraocular pressure, lens, and fundus. Check temperature, meningism (neck stiffness, Kernig and Brudzinski signs), rash, cranial nerves, fundi for papilloedema, and perform a neurological examination.

Red flags

• Fever, neck stiffness, rash, drowsiness or confusion (meningitis, encephalitis)
• Sudden severe headache (subarachnoid haemorrhage)
• Papilloedema, vomiting and headache (raised intracranial pressure)
• Reduced vision, corneal opacity, hypopyon or irregular pupil
• Severe eye pain, halos or fixed mid-dilated pupil (angle closure)
• Contact lens wearer with pain (corneal ulcer)
• Chemical, penetrating or ultraviolet injury
• Herpes zoster rash on the forehead or nose
• Head injury or concussion with persistent photophobia and neurological signs
• Immunosuppression

Special groups.

• Children: meningitis, keratitis (herpes), uveitis of juvenile idiopathic arthritis (often painless), and albinism
• Pregnancy: migraine and pre-eclampsia
• Older adults: herpes zoster ophthalmicus
• Region specific: trachoma, onchocerciasis, measles keratitis and vitamin A deficiency

Ocular

• Corneal abrasion and foreign body, ultraviolet keratitis, chemical injury
• Infectious keratitis (bacterial, fungal, acanthamoeba), herpes simplex keratitis, herpes zoster ophthalmicus, adenoviral keratoconjunctivitis
• Anterior uveitis (HLA-B27 related, herpetic, sarcoid, tuberculous, syphilitic, Behcet, juvenile idiopathic arthritis), posterior uveitis, endophthalmitis
• Acute angle closure glaucoma, congenital glaucoma, scleritis, dry eye and blepharitis, contact lens overwear
• Mydriasis (drug induced, traumatic, third nerve palsy), iris defects (aniridia, albinism, coloboma), post-surgical, cataract and aphakia, retinal dystrophy and cone dystrophy, achromatopsia

Neurological

• Migraine (with or without aura), tension type headache, cluster headache
• Meningitis (bacterial, viral, tuberculous, cryptococcal), encephalitis, subarachnoid haemorrhage
• Raised intracranial pressure (tumour, idiopathic intracranial hypertension, hydrocephalus)
• Post-concussion syndrome and traumatic brain injury, thalamic stroke, Chiari malformation
• Blepharospasm, trigeminal neuralgia, optic neuritis, Parkinson disease and progressive supranuclear palsy

Systemic, drug related and other

• Botulism, tetanus, rabies (hydrophobia and photophobia), measles, hepatitis
• Drug induced (anticholinergics, sympathomimetics, quinine), vitamin A deficiency, riboflavin deficiency
• Fibromyalgia and chronic fatigue, depression, anxiety, post-traumatic stress disorder, autism spectrum conditions

Reasoning. Examine the eye first. If the eye is quiet and the pupils normal, look for neurological and systemic causes. Do not miss meningitis or subarachnoid haemorrhage in the presence of fever, neck stiffness or sudden headache.

First line. Visual acuity, pupils, fluorescein staining, slit lamp, intraocular pressure, temperature, neck stiffness, fundoscopy, and neurological examination.

Targeted tests.

• Corneal scrape for Gram stain, culture and polymerase chain reaction (herpes simplex and zoster) in severe or atypical keratitis; conjunctival swab for adenovirus.
• Uveitis work up for recurrent, bilateral, severe or granulomatous disease: HLA-B27, full blood count, ESR, C reactive protein, angiotensin converting enzyme, syphilis serology, interferon gamma release assay, chest radiograph, antinuclear antibody and urinalysis; sacroiliac imaging with back pain.
• Blood cultures, lumbar puncture (after imaging when indicated) with opening pressure, cell count, protein, glucose, Gram stain, culture, viral polymerase chain reaction, cryptococcal antigen, and acid fast bacilli; CT head before puncture when focal signs, reduced consciousness or papilloedema.
• Non-contrast CT head within minutes for sudden severe headache; lumbar puncture at least 12 hours after onset if CT is normal after 6 hours; CT angiography as an alternative.
• MRI brain with contrast for suspected intracranial pathology, post-concussion, or persistent unexplained photophobia.
• Blood tests for vitamin A, riboflavin, and thyroid function when indicated.

Limitations. Meningism may be absent early and in infants and older adults. Early CT can be normal in subarachnoid haemorrhage after 6 hours. Migraine is a diagnosis of exclusion when atypical features are present.

Meningitis and encephalitis (emergency). Give immediate ceftriaxone 2 g IV every 12 hours with dexamethasone 10 mg IV every 6 hours for 4 days (first dose before or with the antibiotic). Add ampicillin 2 g IV every 4 hours if age over 60 or immunocompromised. Add aciclovir 10 mg/kg IV every 8 hours (adjusted to creatinine clearance) for suspected encephalitis. Do not delay antibiotics for imaging or puncture.

Subarachnoid haemorrhage (emergency). Non-contrast CT head, then neurosurgical referral. Avoid hypotension. Give paracetamol 1 g IV or orally every 6 hours for pain, and reverse anticoagulants. Give nimodipine 60 mg orally or by nasogastric tube every 4 hours for 21 days, started within 96 hours (30 mg every 2 hours if blood pressure falls; 30 mg every 4 hours in cirrhosis).

Acute angle closure glaucoma.

• Acetazolamide 500 mg IV or orally then 250 mg orally every 6 hours (avoid in sulphonamide allergy and severe renal impairment)
• Timolol 0.5 percent 1 drop (avoid in asthma, heart block, bradycardia)
• Apraclonidine 1 percent 1 drop
• Pilocarpine 2 percent 1 drop once pressure is falling
• Same day ophthalmology for laser iridotomy

Keratitis and corneal ulcer. Same day ophthalmology. After scraping, give ofloxacin 0.3 percent or moxifloxacin 0.5 percent 1 drop every 15 to 60 minutes initially, with cycloplegic drops (cyclopentolate 1 percent 1 drop twice daily). Fungal and acanthamoeba disease need specialist antimicrobial therapy (natamycin 5 percent).

• Herpes simplex keratitis: aciclovir 3 percent ointment 5 times daily until healed and for at least 3 days after. Avoid steroids in epithelial disease.
• Herpes zoster ophthalmicus: valaciclovir 1 g orally three times daily for 7 days. Adjust for kidney function: creatinine clearance 30 to 49 mL/min, 1 g every 12 hours; 15 to 29 mL/min, 1 g daily; under 15 mL/min, 500 mg daily.

Anterior uveitis. Ophthalmology: prednisolone acetate 1 percent 1 drop every 1 to 2 hours, tapered over 4 to 6 weeks, and cycloplegic drops (cyclopentolate 1 percent twice to three times daily, or atropine 1 percent once daily). Treat associated systemic disease. Recurrent disease may need adalimumab or other immunosuppression by specialists.

Corneal abrasion, foreign body and ultraviolet keratitis. Remove foreign body. Give chloramphenicol 0.5 percent drops 4 times daily or ointment 3 to 4 times daily for 5 days, lubricants, oral analgesia (paracetamol 1 g every 4 to 6 hours, ibuprofen 400 mg every 6 to 8 hours), and cycloplegic drops for severe pain. Review at 24 to 48 hours. No patching.

Chemical injury. Immediate irrigation with at least 1 to 2 L of saline or water until the pH is 7.0 to 7.4, then same day ophthalmology.

Migraine. Dark quiet room, early treatment.

• Sumatriptan 50 to 100 mg orally at onset (repeat after 2 hours if the first dose helped; maximum 300 mg in 24 hours). Contraindicated in ischaemic heart disease, stroke, uncontrolled hypertension and with ergots or monoamine oxidase inhibitors.
• Plus ibuprofen 400 to 600 mg (maximum 2.4 g in 24 hours) or aspirin 900 mg or paracetamol 1 g (maximum 4 g in 24 hours).
• Metoclopramide 10 mg orally, IM or IV every 8 hours (maximum 30 mg in 24 hours; 5 days).
• Prevention for 4 or more headache days each month: propranolol 40 mg orally twice daily increased every 2 weeks to a usual 80 to 160 mg daily (maximum 240 mg daily); amitriptyline 10 mg at night increased by 10 mg weekly to 25 to 75 mg; or topiramate 25 mg at night increased by 25 mg weekly to 50 mg twice daily (teratogenic; halve when creatinine clearance is under 70 mL/min).

Raised intracranial pressure. Neurosurgical care. Idiopathic intracranial hypertension: weight loss and acetazolamide 500 mg orally twice daily increased by 500 mg weekly to a maximum of 4 g daily as tolerated.

Post-concussion photophobia. Graded return to activity, treatment of headache and sleep, tinted lenses (FL 41 or rose tinted), and neurology, neuro-ophthalmology or vestibular rehabilitation for persistent symptoms.

Blepharospasm and light sensitivity. Botulinum toxin injections by a specialist.

Dry eye. Lubricants (hypromellose 0.3 percent or sodium hyaluronate 0.1 to 0.2 percent, 1 drop 4 to 6 times daily, preservative free when frequent), lid hygiene, and ciclosporin 0.05 percent drops twice daily by ophthalmology for moderate to severe disease.

Drug induced and mydriasis. Withdraw the drug when possible, and wear sunglasses.

Vitamin A deficiency. Retinol 200,000 units orally on days 1, 2 and 14 for adults and children over 12 months (100,000 units for 6 to 11 months; 50,000 units for under 6 months). Avoid in pregnancy except for severe deficiency under specialist direction.

Albinism and cone dystrophy. Tinted or photochromic lenses, brimmed hats, low vision services, and genetic counselling.

Symptomatic measures. Sunglasses and brimmed hat outdoors. Avoid constant indoor tinted lenses (can worsen light sensitivity by adaptation). Reduce screen brightness. Gradual re-exposure to light for chronic non-inflammatory photophobia.

Monitoring. Review at 24 to 48 hours for keratitis and abrasion, at 1 week for uveitis, and at 4 to 6 weeks for migraine treatment. Monitor intraocular pressure with steroid drops.

Referral and escalation. Same day ophthalmology for any eye with pain, red eye or reduced vision. Immediate emergency care for suspected meningitis or subarachnoid haemorrhage. Neurology for migraine refractory to treatment, post-concussion syndrome and unexplained photophobia. Public health notification for meningococcal disease, measles and other notifiable diseases.

Admission criteria. Meningitis, encephalitis, subarachnoid haemorrhage, angle closure not settling, corneal ulcer needing intensive treatment, endophthalmitis, or neurological deterioration.

Discharge and safety netting. Return urgently for fever, stiff neck, severe headache, rash, drowsiness, confusion, reduced vision, increasing eye pain, or worsening photophobia.