Name the condition

Here we see a wonderful image of an inferior temporal branch retinal artery occlusion. All arterial occlusions need to be treated as a medical emergency requiring medical intervention. This might be an ocular emergency, if it is known to be recent, or a general medical concern because of the potential for further occlusion affecting the opposite eye, or worse still, the brain, heart or lung.

It should be remembered that arteries and arterioles are flexible, walled 'pipes' which contain high pressure fluid. In order to block or restrict flow there needs to be a significantly resilient embolus. This is most likely to be calcific in origin as a lump of calcium may lodge at a bifurcation and block flow. Calcific emboli tend to slough from atheromatous plaques, small build-up of material (cholesterol, platelets, calcium and so on) within the vessel walls, particularly at points of bestilled blood next to an area of turbulence. Such sites are found at the mitral valve of the heart and the point of branching of the common carotid into the internal and external carotid arteries. Material from these plaques (which build up with age and have an association with smoking and poorer diet) can pass quickly to the eye (from the heart via aorta, common carotid, internal carotid, ophthalmic, central retinal or ciliary arteries), making involvement of the eye potentially a first warning sign of atheromatous disease.

Cholesterol emboli tend to be lamellar and blood can squeeze past. They may be seen as Hollenhorst's plaques on the fundus, but not necessarily reducing blood flow. Platelet and clotting material tends to pass through the vascular tree in 'trains' of emboli, causing a temporary blood reduction and a temporary curtain loss of vision, often termed amaurosis fugax. Calcium, however, is typically occlusive.

If the vision loss is within a few hours of presentation, then emergency referral to an eye unit may result in some sight being saved. Attempts at dislodging the embolus further (either as a first aid measure by massage and breathing exhaled breath) may help, but emergency intravenous acetazolamide may drop pressures enough to help move along the embolus.

If the vision loss is less recent, it is important to remember that even though the vision loss is not likely to be permanent, this patient may well have further emboli ready to happen and affecting the other eye or causing stroke, coronary, or pulmonary supply - potentially fatal events.

For this reason, in the event of any arterial occlusion, medical help should be sought. If longer than 12 hours, this may be the patient's GP or a local general hospital. I have heard students say: 'If an occlusion is older than 12 months, nothing can be done so just review.' This is wrong! ?