IRMA: Intraretinal microvascular abnormalities

Intraretinal microvascular abnormalities (IRMA) represent either new vessel growth or remodeling of preexisting vessels through endothelial cell proliferation within the retinal tissues to act as shunts through areas of nonperfusion.

More extensive retinal hypoxia triggers compensatory mechanisms within the eye to provide enough oxygen to tissues. Venous caliber abnormalities, such as venous beading, loops, and dilation, signify increasing hypoxia and almost always are seen bordering the areas of capillary nonperfusion

Intraretinal microvascular abnormalities

• Remodeled capillary beds without proliferative changes
• Collateral vessels that do not leak on fluorescein angiography
• Usually can be found on the borders of the nonperfused retina