How does blockage of a retinal vein cause swelling and bleeding in the retina?

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eye disease An ophthalmologist performing LASIK eye surgery.

When a retinal vein becomes blocked, it causes a "damming up" of blood within the eye. This obstruction prevents the normal outflow of blood from the retina, leading to a significant increase in pressure within the vascular system.1

This pressure causes small blood vessels to burst, resulting in multiple hemorrhages scattered across the retinal surface. Furthermore, the congestion leads to retinal swelling as fluid accumulates in the tissue. While the severity of vision loss depends on whether a branch or the central vein is affected, some degree of recovery is common.1