What causes the bright red patches in the conjunctiva?

Bright red patches in the conjunctiva, commonly referred to as subconjunctival hemorrhages, are primarily caused by the rupture of small blood vessels in the eye. This can occur due to various reasons, such as trauma, excessive coughing, or straining. When these blood vessels break, blood leaks into the space between the conjunctiva (the clear membrane covering the white part of the eye) and the underlying sclera, leading to the bright red appearance that can be quite striking.

Understanding other potential causes of conjunctival changes is important for accurate diagnosis. Accumulation of bilirubin could lead to jaundice, which would cause a yellowing rather than red patches. Localized swelling may indicate inflammation or allergic reactions, but it would manifest differently, often appearing as a bump or swollen area rather than a distinct patch of red. Infections can cause redness due to inflammation, but they typically present alongside other symptoms like discharge, pain, and itching, rather than isolated bright red patches. Thus, the rupture of blood vessels stands out as the most direct cause of the bright red patches in the conjunctiva.