Keratoconjunctivitis
Summary
Keratoconjunctivitis is inflammation of both the cornea (keratitis) and conjunctiva (conjunctivitis), presenting with eye redness, pain, photophobia, tearing, and foreign body sensation. Common causes include viral infections (especially adenovirus - epidemic keratoconjunctivitis), herpes simplex virus, and autoimmune/dry eye conditions like keratoconjunctivitis sicca (Sjögren syndrome). It is highly contagious in viral forms and a common cause of 'pink eye' outbreaks.
Detail
Keratoconjunctivitis involves combined corneal and conjunctival inflammation, distinguishing it from isolated conjunctivitis by corneal involvement, which carries higher risk of visual impairment. Key etiologies: (1) Epidemic keratoconjunctivitis - caused by adenovirus (serotypes 8, 19, 37), highly contagious via fomites/direct contact, presents with watery discharge, preauricular lymphadenopathy, subepithelial corneal infiltrates that can cause prolonged photophobia and blurred vision; self-limited but supportive care (cold compresses, artificial tears) is mainstay since no specific antiviral exists. (2) Herpetic keratoconjunctivitis (HSV-1) - presents with dendritic corneal ulcers seen on fluorescein staining, treated with topical/oral antivirals (acyclovir, trifluridine); corticosteroids are contraindicated as they worsen HSV keratitis and can lead to corneal perforation. (3) Keratoconjunctivitis sicca (dry eye syndrome) - due to decreased tear production, associated with Sjögren syndrome (also causes xerostomia), diagnosed via Schirmer test, treated with artificial tears, cyclosporine drops, or punctal plugs. (4) Vernal keratoconjunctivitis - allergic, seen in young males, associated with atopy, giant papillae on tarsal conjunctiva. (5) Superior limbic keratoconjunctivitis - associated with thyroid disease. Clinical pearls for boards: distinguish bacterial (purulent discharge, treat with antibiotics) vs viral (watery discharge, preauricular nodes, self-limited) vs allergic (itching, bilateral, cobblestone papillae) conjunctivitis. Always evaluate for corneal involvement with fluorescein staining and slit lamp exam if keratitis suspected, as this changes management and prognosis. Avoid steroids without ophthalmology guidance due to risk of worsening herpetic or fungal infections.
Sources
- First Aid for the USMLE Step 1
- Vaughan & Asbury's General Ophthalmology
- UpToDate: Conjunctivitis
- Basic and Clinical Science Course (BCSC) - External Disease and Cornea, American Academy of Ophthalmology
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