A 15-year-old presents with blood in the eye after coughing. What is the most likely diagnosis?

Blood in the eye following a cough is most commonly associated with subconjunctival hemorrhage. This occurs when small blood vessels in the conjunctiva break, allowing blood to pool under the surface of the eye. It can be caused by a variety of factors, including sudden increases in pressure, such as from a forceful cough or a sneeze.

The presentation of red or bloodshot eyes without other significant symptoms is characteristic of subconjunctival hemorrhage, which often resolves on its own without the need for treatment. In a young individual, such as a 15-year-old, who might cough forcefully due to illness or other reasons, this type of bleeding is quite prevalent and typically harmless.

Other options like hyphema involve blood in the anterior chamber of the eye, which usually presents with a different mechanism of injury and is often more serious. Corneal abrasion would show signs of pain and irritation and is related to injury of the cornea, while a retinal tear would typically present with symptoms such as floaters, flashes of light, or sudden vision loss, indicating more severe underlying issues.