Central Retinal Artery Occlusion

Question 1

What is central retinal artery occlusion?

Answer 1

Central retinal artery occlusion occurs where something blocks the flow of blood through the central retinal artery.

Question 2

Briefly describe the anatomy of the retinal artery

Answer 2

The central retinal artery supplies the blood to the retina. It is a branch of the ophthalmic artery, which is a branch of the internal carotid artery.

Question 3

What causes central retinal artery occlusion?

Answer 3

The most common cause of occlusion of the retinal artery is atherosclerosis. It can also be caused by giant cell arteritis, where vasculitis affecting the ophthalmic or central retinal artery causes reduced blood flow.

Question 4

What are the risk factors for central retinal artery occlusion?

Answer 4

Risk factors for retinal artery occlusion by atherosclerosis are the same as for other cardiovascular diseases:

• Older age
• Family history
• Smoking
• Alcohol consumption
• Hypertension
• Diabetes
• Poor diet
• Inactivity
• Obesity

Those at higher risk for retinal artery occlusion secondary to giant cell arteritis are white patients over 50 years of age, particularly females and those already affected by giant cell arteritis or polymyalgia rheumatica.

Question 5

What are the clincial features of central retinal artery occlusion?

Answer 5

Blockage of the central retinal artery causes sudden painless loss of vision.

Question 6

How does central retinal artery occlusion present on swinging light test?

Answer 6

There will be a relative afferent pupillary defect.

This is where the pupil in the affected eye constricts more when light is shone in the other eye compared when it is shone in the affected eye. This occurs because the input is not being sensed by the ischaemic retina when testing the direct light reflex but is being sensed by the normal retina during the consensual light reflex.

Question 7

Why is there a relative afferent pupillary defect in central retinal artery occlusion?

Answer 7

This is where the pupil in the affected eye constricts more when light is shone in the other eye compared when it is shone in the affected eye. This occurs because the input is not being sensed by the ischaemic retina when testing the direct light reflex but is being sensed by the normal retina during the consensual light reflex.

Question 8

How does central retinal artery occulusion present on fundoscopy?

Answer 8

Fundoscopy will show a pale retina with a cherry-red spot. The retina is pale due to a lack of perfusion with blood. The cherry-red spot is the macula, which has a thinner surface that shows the red coloured choroid below and contrasts with the pale retina.

Question 9

Briefly describe the management of giant cell arteritis

Answer 9

Giant cell arteritis is an important potentially reversible cause. Therefore older patients are tested and treated for this if suspected. Testing involves an ESR and temporal artery biopsyand treatment is with high dose steroids (i.e. prednisolone 60mg).

Question 10

Briefly describe the immediate management of central retinal artery occlusion

Answer 10

Patients with suspected central retinal artery occlusion should be referred immediately to an ophthalmologist for assessment and management.

If the patient presents shortly after symptoms develop then there are certain things that can be tried to attempt and dislodge the thrombus. None of these have a strong evidence base. Some examples are:

• Ocular massage
• Removing fluid from the anterior chamber to reduce intraocular pressure.
• Inhaling carbogen (a mixture of 5% carbon dioxide and 95% oxygen) to dilate the artery
• Sublingual isosorbide dinitrate to dilate the artery

Question 11

Briefly describe the long term management of central retinal artery occlusion

Answer 11

Long term management involves treating reversible risk factors and secondary prevention of cardiovascular disease.