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Approach to a Red Eye

Jonathan A. Barnett

When the conjunctiva is vasodilated, or “injected,” the eye looks red. The more inflamed the conjunctiva, the angrier-looking the eye.

Differential for Red Eye:

  • Dry Eye

    • Trace diffuse injection, blurry vision that fluctuates, gritty sensation, clears with blinking
  • Corneal abrasion / ulceration / exposure keratopathy

    • Unilateral, moderate to severe injection, may be diffuse or sectoral, pain, blurry vision, mucus discharge, history of poor blink rate, intubated/sedated status.
  • Subconjunctival hemorrhage

    • Patch of bright red, often with sharp borders. Due to rupture of conjunctival vessel. Whole conjunctiva can be involved and may be bright red. Looks scarier than it is. Common in patients on anticoagulation or after a Valsalva event (e.g., coughing). Will resolve spontaneously.
  • Allergic conjunctivitis

    • Chemosis, mild to moderate injection, blurry vision, very itchy, watery discharge, hx of allergies/atopy
  • Viral or Bacterial conjunctivitis

    • Moderate to severe injection, scattered subconjunctival hemorrhages or petechiae, itchy or burning/painful eyes. If viral, look for preauricular adenopathy or recent URI.
  • Acute angle closure glaucoma

    • Severe eye pain with nausea/vomiting, rock-hard eye, mid-dilated and fixed pupil, blurry vision
  • Uveitis/Episcleritis/Scleritis

    • Eye pain, perilimbal injection (“ciliary flush”), blurry vision, may have history of autoimmune disease. Episcleritis vs Scleritis can be difficult to discern. Scleritis may have a deeper, violaceous hue.
  • Endophthalmitis

    • Eye pain, history of trauma or eye surgery, severe vision loss, history of immunocompromise and systemic infection (if endogenous)
  • Carotid-cavernous fistula

    • Engorged and tortuous conjunctival vessels, recent history of trauma, resistance to retropulsion (pushing the globe back in)