What is the typical reason for the onset of a subconjunctival hemorrhage?

The typical reason for the onset of a subconjunctival hemorrhage often relates to an increase in intraocular pressure. When there is a sudden spike in this pressure, it can cause blood vessels in the conjunctiva to rupture, leading to the characteristic bright red patch on the white part of the eye. This can occur during activities that transiently increase pressure, such as heavy lifting, severe coughing, or straining.

In contrast, while infections, allergies, and trauma can cause various eye conditions, they are less commonly associated with a spontaneous subconjunctival hemorrhage. Infection may cause redness and discharge but usually involves accompanying symptoms, while allergies can lead to irritation and tearing. Trauma, on the other hand, could indeed cause a hemorrhage, but it is not the most common reason for occurrences that arise without a clear cause. Thus, an increase in intraocular pressure stands out as the primary mechanism leading to subconjunctival hemorrhages.