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Red eye always presents the signs and symptoms of eye discharge, redness, pain, photophobia, itching, and visual changes. And indicates the intraocular or extraocular inflammation of the eye. It can be managed by primary care. There are four common causes of red eye. Conjunctivitis is the most common cause of red eye. Trauma, glaucoma and iritis are the other three common causes of red eye.

Conjunctivitis is always caused by bacterial, viral, allergies or irritants factor. But there is no specific diagnostic method to distinguish viral from bacterial conjunctivitis. The presence or absence of preauricular lymph node involvement can tell the viral or not. Adenovirus is the most common cause of viral conjunctivitis, and other causes include enterovirus, coxsackievirus, varicella zoster virus, Epstein-Barr virus, herpes simplex virus, and influenza. You could distinguish allergies by hypersensitiveness history. We usually treated conjunctivitis with broad-spectrum antibiotics of eye drops in multiple, except you were very sure what the real factor of conjunctivitis was. Fortunately, conjunctivitis rarely leads to serious complications. Severe cases may be complicated by subepithelial corneal opacities and pseudomembranes. Herpes simplex virus would leads to serious complications such as keratitis, if repeated, the patient would be blind, eventually need corneal transplants(PKP).

Other common causes of red eye include blepharitis, corneal abrasion, foreign body, subconjunctival hemorrhage, keratitis, chemical burn, and scleritis.