A localized dilation of microvasculature formed due to disruption of the internal elastic lamina of a retinal capillary blood vessel. The lesions present as small circular, red dots having distinct margins and are no larger than a blood vessel width at the disk margin. This expansion disturbs the normal flow pattern, changing shear force and pressure along the vessel. Shear force plays a key role in promoting the differentiation and proliferation of endothelial cells. [from
HPO]