Central Retinal Artery Occlusion: An Overview

Amal Minocha MBBS, BSc (Hons)1
1 Royal Free Hospital, London.

Introduction

Central retinal artery occlusion (CRAO) refers to a sudden blockage of the central retinal artery. It is an ophthalmic emergency that can result in profound visual impairment. The Central retinal artery (CRA) is a branch of the ophthalmic artery which is a branch of the internal carotid artery. The CRA is the main blood supply to the inner retinal layers whereas the outer retina is supplied by the choriocapillaris of the choroid which branches off the ciliary artery (1). CRAO has an incidence of 1 in 100,000 people and is responsible for 1 in 10,000 outpatient ophthalmology appointments. It most commonly affects patients over the age of 60 with men affected more than women (2).

This article will provide a brief outline on the pathophysiology, diagnosis, investigations, and management of CRAO.

Pathophysiology 

CRAO is considered a form of an acute ischaemic stroke. The underlying aetiology of CRAO is most commonly embolic in nature as a result of atherosclerotic disease. Risk factors are similar to those for other thromboembolic diseases and include smoking, diabetes, hyperlipidaemia, hypercoagulable states and hypertension (3).

Symptoms and Diagnosis

Patients with CRAO often present with acute painless monocular vision loss. In about 1-2% of patients, the vision loss might be a bilateral. There may be a preceding history of amaurosis fugax. Visual acuity can vary between loss of light perception to finger counting.

Examination of the external eye, anterior chamber, extraocular eye movements and intraocular pressure are usually normal. Fundoscopy of the retina often shows a diffusely pale with a cherry red spot- this is due to preserved choroidal circulation beneath the fovea. Arteriolar emboli can sometimes be visualised on fundoscopic examination (3).

Physical examination is important in assessment of CRAO in particular examining pulse rate and rhythm for atrial fibrillation which can explain embolic phenomena. Temporal arteritis is an important cause to exclude so examination for scalp tenderness should be conducted.

Investigations

In addition to an eye examination and fundoscopy workup for CRAO should include fluorescein angiography, bloods including C-reactive protein, erythrocyte sediment rate (ER), platelet count (to exclude arteritic causes of CRAO). Vascular work up should also include assessment of blood pressure, cholesterol and fasting blood sugar as patients presenting with CRAO often have previously undiagnosed vascular risk factors (4). Duplex carotid ultrasound and echocardiogram can also be done to investigate for other embolic sources. Younger patients should have further investigation including screening for vasculitides and coagulopathies.

Management

CRAO is an ocular emergency which requires urgent ophthalmic review as the retina can be irreversibly damaged rapidly. Although there are several management strategies employed for CRAO, there is no consensus on treatment nor is there any evidence-based guideline for treatment. Treatment options in the acute management of CRAO include:

  • Ocular massage to dislodge an emboli
  • Utilisation of sublingual isosorbide dinitrate, inhaled carbogen or hyperbaric oxygen to cause dilation of the artery (increasing oxygenation to the retina)
  • Lowering intraocular pressure by using paracentesis (to remove fluid from the front of the eye or using medication such as mannitol, beta-blockers and intravenous acetazolamide.
  • Thrombolytic therapy, either delivered intravenously or intra-arterially. Some observational studies have demonstrated recovery of vision while more recent randomised controlled trials did not show efficacy. Most studies agree that thrombolytic therapy is only likely to be effective when employed within the first 6 hours of symptom onset. (5)
  • High dose steroids immediately if temporal/giant cell arteritis is suspected.  

The longer-term management of CRAO involves addressing underlying vascular risk factors to prevent further eye or end organ damage- this includes treating hyperlipidaemia, diabetes and hypertension. Patients often have ophthalmic follow up to assess for complications including glaucoma and vitreous haemorrhage which can occur because of iris neovascularisation.

Conclusion

CRAO is an ocular emergency that can have a profound impact on vision. It is analogous to that of a cerebral stroke and thus investigation and addressing of vascular risk factors are important to prevent further end organ damage. Although there is no consensus on the treatment for CRAO, early management and intervention is key in preventing visual loss and other thromboembolic events.

References

1. Hayreh SS. Physiological Anatomy of the Retinal Vasculature. In: Encyclopedia of the Eye [Internet]. Elsevier; 2010 [cited 2022 Jan 19]. p. 431–8. Available from: https://linkinghub.elsevier.com/retrieve/pii/B9780123742032001718

2. Varma DD, Cugati S, Lee AW, Chen CS. A review of central retinal artery occlusion: clinical presentation and management. Eye Lond Engl. 2013 Jun;27(6):688–97.

3. Farris W, Waymack JR. Central Retinal Artery Occlusion. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 [cited 2022 Jan 19]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK470354/

4. Rudkin AK, Lee AW, Chen CS. Vascular risk factors for central retinal artery occlusion. Eye. 2010 Apr;24(4):678–81.

5. Cugati S, Varma DD, Chen CS, Lee AW. Treatment Options for Central Retinal Artery Occlusion. Curr Treat Options Neurol. 2013 Feb;15(1):63–77.

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