Pathology Involving the Retina

Sudden Visual Loss Basic Science and Pathophysiology Pathology Involving the Retina

Central retinal artery occlusion

Fig.6 Central retinal artery occlusion – image by Dr. Gopal Bisht, via Wikimedia Commons

Central retinal artery occlusion (CRAO) can occur as a thrombotic, embolic or arteritic phenomenon.

The majority of CRAOs are caused by platelet fibrin thrombi and emboli as a result of atherosclerotic disease and account for over two-third of all CRAO cases.

Central retinal vein occlusion

Fig.7 Central retinal vein occlusion – image by Werner JU et al. via Wikimedia Commons

Venous occlusion may occur either in a branch or in the central retinal vein itself and is more common in those over 65 years. [6]

Retinal vein occlusion is due to thrombosis within retinal veins. The main associations can be defined as risk factors for atherosclerosis, and the remainder are conditions that cause hyperviscosity or slow or turbulent flow through retinal veins.

It is most common where arteries and veins cross in the retina, and in the head of the optic nerve. Progressive thickening of the arterial wall can lead to venous occlusion within the sheath (see Fig.8 below).

Fig.8 Retinal vein occlusion adapted from Smart Servier