Why can diabetic retinopathy cause retinal swelling and vision loss?

Diabetic retinopathy occurs when excess glucose in the blood damages the small blood vessels within the retina.12

This damage weakens the vessel walls, causing them to leak fluid into the surrounding retinal tissue. This leakage leads to retinal swelling, a condition known as macular edema, which is a primary cause of vision loss in patients with diabetes.123

Vision loss can also result from ischemia, where areas of the retina no longer receive adequate blood flow due to the vascular damage. In more advanced stages, the disease may progress to proliferative diabetic retinopathy, characterized by the growth of fragile, abnormal blood vessels. These vessels are highly susceptible to bleeding into the vitreous cavity and can lead to retinal detachment, further threatening sight.312