38) Acute Occlusion of Central Retinal Artery And Its Branches
Definition
Retinal artery occlusion refers to obstruction or blockage of the retinal vascular lumen by an embolus, thrombus or inflammatory/ traumatic vessel wall damage or spasm. The lack of oxygen delivery to the retina during this blockage may result in severe loss of vision.
Aetiology
Occlusion (usually embolic, but can be thrombotic, inflammatory or traumatic) of the blood flow in the retinal blood vessel. The main artery supplying the globe is the ophthalmic artery. The portion of the ophthalmic artery that enters the eye at the optic nerve is called the central retinal artery (CRAO). This artery then divides into a superior and an inferior branch retinal artery that each then further subdivides to supply retinal vessels to the retina.
Epidemiology
Atherosclerosis, cardiac (valvular, myxoma) disease and other disorders contributing to embolus formation; coagulopathies (sickle cell, homocysteine, pregnancy, platelet and factor abnormalities), collagen vascular diseases, ocular abnormalities (arterial loops, optic disc drusen) and other (migraine, hypotension, trauma). Most patients are in their 60’s; more men than women are affected. Only 1-2 % are bilateral.
Clinical Features
Patients usually complain of the acute onset of visual loss. Patients with central retinal artery occlusion complain of visual loss over the entire field of vision. Patients with a branch retinal artery occlusion complain of focal loss of their field of vision. The loss of vision is usually painless.
Diagnostic Imaging
Electroretinography, shows a characteristic diminution of the b-wave.
A carotid ultrasound duplex scan to determine whether there are carotid plaques present. Cardiac echocardiography is also useful to look for sources of emboli