Differential Diagnosis for Redness on the Lateral Side of the Eye
Single Most Likely Diagnosis
- Subconjunctival Hemorrhage: This condition is characterized by the appearance of a bright red patch on the white of the eye, often resulting from a broken blood vessel. It can occur spontaneously or due to trauma, coughing, or straining. The description of the lateral side of the eye looking like a blood vessel strongly suggests this diagnosis.
Other Likely Diagnoses
- Conjunctivitis: This is an inflammation or infection of the outer membrane of the eyeball and the inner eyelid. It can cause redness, itching, and discharge. While it typically affects the entire eye, it could initially present on one side.
- Blepharitis: Inflammation of the eyelids can cause redness, swelling, and sometimes a feeling of having something in the eye. It might initially be noticed on one side, including the lateral aspect.
- Dry Eye Syndrome: This condition can lead to irritation and redness of the eyes, which might be more noticeable on one side, depending on the environmental exposure or the anatomy of the individual's eyes.
Do Not Miss Diagnoses
- Angle-Closure Glaucoma: Although less common, this is a medical emergency that can cause redness of the eye, along with severe pain, blurred vision, and sometimes nausea and vomiting. It's crucial to rule out this condition due to its potential for permanent vision loss if not promptly treated.
- Cellulitis (Periorbital or Orbital): An infection of the skin and tissues around the eye can cause redness, swelling, and warmth. It requires immediate medical attention to prevent serious complications, including vision loss.
Rare Diagnoses
- Kaposi's Sarcoma: A type of cancer that can cause lesions on the skin, including the area around the eyes. It might appear as red, purple, or brown patches.
- Sjögren's Syndrome: An autoimmune disorder that can cause dry eyes and mouth. While it's more systemic, the eye symptoms could initially be unilateral.
- Carotid-Cavernous Fistula: An abnormal connection between the carotid arteries and cavernous sinuses that can lead to redness and swelling of the eye, among other symptoms. It's a rare but serious condition that requires prompt medical attention.