According to EYEWiki:
Red Eyes is a non-specific term to describe an eye that appears red due to illness, injury, or some other condition, conjunctivitis and subconjunctival hemorrhage being two of the less serious but more common causes. The goal of the primary care doctor presented with a red eye is to assess whether it is in need of emergent referral and action, or can be managed easily and effectively without additional resources. The term usually refers to hyperemia of the superficial blood vessels of the conjunctiva, sclera or episclera, and may be caused by diseases or disorders of these structures or adjacent structures that may affect them directly or indirectly.
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