Differential Diagnosis for a Red Eye

The differential diagnosis for a red eye is broad and can be categorized into several groups. Here's a breakdown of potential causes, organized by their likelihood and potential impact:

• Single Most Likely Diagnosis

  • Conjunctivitis: This is often the first consideration for a red eye due to its high prevalence. It can be caused by viruses, bacteria, or allergens, leading to inflammation of the conjunctiva, which is the transparent membrane covering the white part of the eye and the inside of the eyelids.

• Other Likely Diagnoses

  • Dry Eye Syndrome: This condition occurs when the eyes do not produce enough tears or the tears are of poor quality, leading to eye irritation and redness.
  • Blepharitis: Inflammation of the eyelids, often associated with a bacterial or demodex mite infestation, can cause redness, itching, and swelling of the eyelids.
  • Subconjunctival Hemorrhage: This condition, characterized by a broken blood vessel under the conjunctiva, can cause sudden onset of redness in one eye, often without pain or vision changes.
  • Uveitis: Inflammation of the uvea, the middle layer of the eye, can cause eye redness, pain, and sensitivity to light, among other symptoms.

• Do Not Miss Diagnoses

  • Acute Angle-Closure Glaucoma: A medical emergency that can cause severe eye pain, redness, blurred vision, and nausea. It occurs when the drainage canals in the eye are suddenly blocked, leading to a rapid increase in intraocular pressure.
  • Endophthalmitis: A severe inflammation of the interior of the eye, usually caused by infection. It is a medical emergency that requires prompt treatment to preserve vision.
  • Orbital Cellulitis: An infection of the tissues surrounding the eye, which can cause redness, swelling, and pain around the eye, and potentially lead to serious complications if not treated promptly.
  • Retinal Detachment: Although it may not always present with redness, it can cause sudden flashes of light, floaters, and a shadow or curtain descending over the field of vision, necessitating urgent medical attention.

• Rare Diagnoses

  • Scleritis: A severe inflammatory disease that affects the sclera (the white part of the eye), causing redness, pain, and tenderness.
  • Keratitis: Inflammation of the cornea, which can be caused by infection or injury, leading to pain, redness, and vision problems.
  • Carotid-Cavernous Fistula: An abnormal connection between the carotid arteries and cavernous sinus, leading to increased pressure in the veins of the face and eye, which can cause redness, swelling, and vision changes.
  • Ocular Migraine: A condition that can cause temporary vision loss or blindness in one eye, accompanied by a headache and sometimes eye redness.

Each of these conditions has distinct features and requires a thorough medical evaluation to determine the correct diagnosis and appropriate treatment.