Differential diagnosis of a "red eye":

Causes of conjunctivitis:

  • Viral
  • Most commonly adenovirus, also HSV
  • Can look similar to bacterial though tends to have more watery/mucoid discharge
  • Pain & itching
  • Other URI sx (e.g. pharyngitis) suggest viral over bacterial
  • Tx = local nafcon/vasocon, check for foreign body; us. lasts 1-2 wks withotu complication; very contagious
  • Bacterial
  • Can look similar to viral though tends to have more purulent discharge
  • More common in children than adults
  • Staphylococcus aureus is the most common organism; also Strep pneumoniae, H. influenzae, M. catarrhalis
  • A meta-analysis of five randomized trials found that 65% of patients with bacterial conjunctivitis improve within 5d regardless of treatment with only rare incidence of severe complications
  • Chlamydial can occur; Consider if doesn't respond to standard treatment; treatment requires systemic antibiotics e.g. doxycycline 100mg BID or erythromycin 500mg QID x 3-6wks
  • Gonococcal conjunctivitis in neonates-Can seriously affect vision; occurs in 10% of infants exposed during delivery even with prophylaxis 
  • Allergic
  • Typical symptoms: itching, redness, tearing, eyelid edema
  • Topical antihistamines can be helpful
  • Levocabastine (Livostin) 1 drop QID (in adults only)
  • Emedastine (Emadine) 1 drop BID for > 3yo
  • Azelastine (Optivar) 1 drop BID for > 3yo
  • Olopatadine (Patanol, Pataday)-Combined mast cell stabilizer/antihistamine 1-2 drops Q6-8h (Patanol) or QD (Pataday) for > 3yo
  • Irritant (e.g. from dust, smoke, chlorine, smog)
  • Treatment includes irritant avoidance, and cool compresses
  • Mast cell stabilizers can be helpful
  • Cromolyn (Crolom, Intal) 1-2 drops Q4-6h for >4yo
  • Nedocromil (Alocril) 1-2 drops BID for > 3yo
  • Angular conjunctivitis
  • Typically chronic, mild infalmmation confined to angles of the eye
  • Most commonly caused by Moraxella axenfeld and treated with tetracycline ointment
  • Distinguishing viral from bacterial conjunctivitis:

    (Sources include Core Content Review of Family Medicine, 2012)