According to the Keith-Wagener-Barker classification, what stage of hypersensitive retinopathy is characterized by swelling of the optic disc?

The Keith-Wagener-Barker classification system outlines four stages of hypertensive retinopathy, each characterized by specific retinal findings. In stage four, also known as malignant hypertension, there is significant damage to the retina and optic nerve, leading to swelling of the optic disc. This disc swelling indicates elevated intracranial pressure or severe hypertension that has progressed beyond the earlier stages.

In contrast, earlier stages (one, two, and three) primarily involve changes such as arteriolar narrowing, cotton wool spots, and retinal hemorrhages, but they do not typically include the optic disc swelling seen in stage four. This swelling is a critical sign of severe hypertension and potential vision-threatening conditions, necessitating immediate clinical attention.