Differential Diagnosis for Bilateral Red Eyes with Headache and Photophobia

• Single most likely diagnosis
  • Viral conjunctivitis: This condition is highly contagious and can cause bilateral red eyes, headache, and photophobia. The absence of itching or discharge makes it less likely to be allergic in nature, pointing more towards a viral etiology.
• Other Likely diagnoses
  • Dry eye syndrome: Although it can cause red eyes and discomfort, the presence of headache and photophobia might suggest a more severe condition. However, it's still a possibility, especially if the patient has a history of dry eye or has been exposed to irritants.
  • Uveitis: This is an inflammation of the uvea, the middle layer of the eye, which can cause pain, redness, and photophobia. It's less common than conjunctivitis but should be considered, especially if the patient has a history of autoimmune diseases.
  • Acute angle-closure glaucoma (in the early stages): While typically characterized by severe pain and vision loss, early stages might present with headache, photophobia, and red eyes. The absence of vision symptoms doesn't rule it out entirely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Meningitis: Although rare, meningitis can present with headache, photophobia, and in some cases, bilateral red eyes due to conjunctival injection. The severity and potential for rapid progression make it a critical diagnosis not to miss.
  • Endophthalmitis: A severe inflammation of the interior of the eye, usually caused by infection. It's a medical emergency and can present with pain, redness, and decreased vision. The absence of discharge doesn't rule it out, especially if the patient has a history of recent eye surgery or trauma.
  • Temporal arteritis: This condition, also known as giant cell arteritis, can cause headache, jaw claudication, and visual disturbances, including photophobia. While less directly associated with bilateral red eyes, it's a diagnosis that could have severe consequences if missed, particularly in older adults.
• Rare diagnoses
  • Sarcoidosis: A systemic disease that can affect the eyes, causing uveitis, among other symptoms. It's less common but should be considered in patients with systemic symptoms or a history suggestive of sarcoidosis.
  • Behçet's disease: A form of vasculitis that can cause a wide range of symptoms, including uveitis and conjunctivitis. It's rare and typically presents with oral and genital ulcers, but the eye symptoms can be a significant part of the disease.