Retinal Arterial Occlusion Flashcards
What is central retinal artery occlusion?
A disease of the eye where the flow of blood through the central retinal artery is occluded
How important is retinal artery occlusion?
Its an ophthalmic emergency
What retinal artery occlusion be divided into?
- Central retinal artery occlusion
- Branch retinal artery occlusion
What is central retinal artery occlusion?
When the CRA occludes before any of its branches
What is branch retinal artery occlusion?
Where one or more of the branches of the CRA are blocked
What are the two sources of blood supply to the retina?
- Central retinal artery
- Ciliary artery
Where does the central retinal artery come from?
It is the first branch of the ophthalmic artery
Where does the ophthalmic artery come from?
It is the first branch of the internal carotid artery
What part of the retina is first supplied by the central retinal artery?
Surface of the optic disc
After supplying the optic disc, what happens to the central retinal artery?
It divides into a superior and inferior branch and then temporal and nasal branches
What do the superior and inferior nasal and temporal branches of the central retinal artery supply?
The 4 quadrants of the retina
What part of the retina does the ciliary artery supply?
The outer retina
How does the ciliary artery supply the retina?
Via the choriocapillaries of the chorid
What anatomical variation is relevant to retinal artery occlusion?
The cilioretinal artery
What percentage of the population are thought to have a cilioretinal artery?
15-30%
What does the cilioretinal artery do?
Supplies the macular retina to varying degrees
What is the importance of the cilioretinal artery to retinal artery occlusion?
It may preserve some central vision in CRA occlusion
How does the cilioretinal artery appear on fundoscopy?
A single vessel emerging from the edge of the optic disc towards macula
What variation does variation in location of occlusion create in retinal artery occlusion?
- Different layers
- Different quadrants
Where in the central retinal artery will an occlusion have the most devastating effect?
More proximal
Why does a more proximal retinal artery occlusion cause a more devastating effect?
It will affect more layers and more areas of the retina
What will occlusion of a distal end branch of the retinal artery affect?
The inner neural layer of the part of the retina supplied
What will a distal retinal end artery occlusion spare?
The photoreceptors (so limits visual loss)
What is central retinal artery occlusion the ocular equivalent of?
Cerebral stroke - it is a process of end organ ischaemia
What is the most common cause of central retinal artery occlusion?
Atherosclerosis
What percentage of central retinal artery occlusion cases are caused by atheroma-related thrombus?
80%
What are some other causes of central retinal artery occlusion?
- Embolism
- Inflammatory disorders
- Thrombophilic disorders
- Infections
- Pharmacological causes
- Ophthalmic causes
Where can an embolus originate to cause central retinal artery occlusion?
- Carotid
- Cardiac
What can cause a carotid embolus?
- Cholesterol
- Fibrinoplatelet
- Calcific embolus
What can cause a cardiac embolus?
- Calcific
- Vegetations from cardiac valve endocarditis
- Mural thrombus e.g. AF
What inflammatory disorders can cause retinal artery occlusion?
- Giant cell arteritis
- Polyarteritis nodosa
- SLE
- Pancreatitis
What thrombophilic disorders can cause retinal artery occlusion?
- Antiphospholipid syndrome
- Protein S or C deficiency
- Leukaemias or lymphomas
What infections can cause retinal artery occlusion?
- Toxoplasmosis
- Syphilis
What are the possible pharmacological causes of retinal artery occlusion?
- OCP
- Cocaine
What are the ophthalmic causes of retinal artery occlusion?
- Severely raised IOP
- Trauma
- Optic nerve drusen
What are the risk factors for retinal artery occlusion?
Same as for atherosclerosis
What is the usual presenting symptom in central retinal artery occlusion?
Sudden (over a few seconds) unilateral painless visual loss
What is vision limited to in the affected eye in 94% of patients with central retinal artery occlusion?
Counting fingers
What percentage of patients with central retinal artery occlusion have bilateral visual loss?
1-2%
What will be seen on examination in retinal artery occlusion?
- RAPD
- Pale retina
- Attenuation of blood vessels
- Cherry-red macula
- Segmentation of blood in arteries
What should systemic examination include in suspected retinal artery occlusion?
- Carotid auscultation for bruits
- Heart sounds for murmurs
- Radial pulse for AF
- BP
How is central retinal artery occlusion diagnosed?
Clinically
Why may investigations be useful in suspected retinal artery occlusion?
To rule out underlying disease
What investigations may be useful in identifying an underlying cause for retinal artery occlusion?
- Urgent ESR and CRP in over 60
- Coagulation studies
- Full blood examination
- Screening tests for vasculitis
- Cardiovascular risk assessment
Why should urgent ESR and CRP be performed in patients presenting with retinal artery occlusion symptoms?
To rule out temporal erteritis
What are the differentials for retinal artery occlusion?
- Retinal detachment
- Vitreous haemorrhage
- Retinal vein occlusion
- Acute glaucoma
- Acute optic neuritis
Why is retinal artery occlusion an emergency?
The retina damage becomes rapidly irreversible
Why is it important to recognise retinal artery occlusion in the long term?
To be able to treat risk factors to protect the other eye and prevent cerebro and cardiovascular incidents
What is the main principle of retinal artery occlusion management?
To attempt to re-perfuse the ischaemic tissue as quickly as possible
What is the best clinically proven treatment for retinal artery occlusion?
There isn’t one but a few things can be tried
What are the options for attempting to reperfuse ischaemic tissue in retinal artery occlusion?
- Firm ocular massage
- Lowering IOP with anterior chamber paracentesis and treatment with acetazolamide
- Dilation of the artery e.g. with sublingual isosorbide dinitrate
- Intra-arterial fibrinolysis through local injection of urokinase into the proximal part of the ophthalmic artery
When can firm ocular massage be used to treat retinal artery occlusion?
90-100 minutes of onset of symptoms
What is a firm ocular massage?
Repeatedly massaging the globe over the closed lid for 10 seconds with 5 second interludes in attempt to dislodge obstruction
What is anterior chamber paracentesis?
Withdrawal of a little fluid from the anterior chamber under local anaesthetic
What is retinal artery occlusion a marker for?
Increased risk of ischaemic end-organ damage e.g. stroke
What are the aims of long-term management following retinal artery occlusion?
- Identify and treat underlying causes
- Assess for coagulopathy
- Reduce risk factors for atherosclerosis
What underlying causes of retinal artery occlusion can be treated in the long-term?
- Investigate and treat hypertension
- Carotid endarterectomy for carotid occlusion
What risk factors for atherosclerosis can be managed to reduce the risk of further ischaemic events following retinal artery occlusion?
- Hypertension
- Prophylaxis with statins and low-dose aspirin
What will patients who have been treated for acute retinal artery occlusion require?
Follow-up in the eye clinic to check for complications
What is the main complications of retinal artery occlusion?
Iris neovascularisation
What can iris neovascularisation lead to?
Glaucoma or vitreous haemorrhage
What are some other potential complications of retinal artery occlusion?
- Retinal neovascularisation
- Rubeosis iridis
- Cells and flare
- Iris necrosis
- Cataract
