By Kateriine Orav, Department of Neurology, North Estonia Medical Centre, Tallinn, Estonia
A patient with acute painless monocular visual loss can be unnerving for the stroke specialist, especially in a centre with no around the clock ophthalmology service. Stroke of the retina caused by central retinal artery occlusion (CRAO) is an under-recognized form of stroke. It is, however, a medical emergency and a recent scientific statement by the American Heart Association highlights the importance of prompt recognition, rapid triage and management of the disease similar to cerebral ischaemic stroke.1
In its natural course CRAO has a poor prognosis in respect to visual recovery with less than 20% of patients experiencing a functional improvement in vision.2 As with cerebral stroke, the most important determinant of retinal damage and final visual outcome is the duration of ischaemia.1 Complete CRAO has been postulated to cause progressive and irreversible retinal ganglion cell death after 12-15 minutes, but factors like collateral blood flow and intermittent reperfusion may allow a longer window of viability.3
For CRAO patients to promptly arrive in the treatment window to a stroke centre infrastructure needs to be in place to rapidly recognize and evaluate patients. Pre-hospital time delay is common in CRAO patients.4 Additional steps compared to the usual stroke code are the necessity of a fundoscopic evaluation to confirm the diagnosis and to exclude other causes such as vitreal or retinal haemorrhage as well as screening for arteritis if there is clinical suspicion. Therefore it is imperative for stroke centres to develop relationships with ophthalmology services to ensure smooth pathways and if necessary use telemedicine solutions to consult on ocular fundus findings.1
There is still much uncertainty about the treatment of CRAO due to the lack of high quality randomized controlled studies and therefore there is a large variability in management strategies between centres.1 Standard treatment options for acute CRAO include intraocular pressure-lowering agents, sublingual isosorbide dinitrate, carbogen and hyperbaric oxygen therapies, but none have proven to be more effective than placebo.5
Intravenous thrombolytic agents have been used off-label to treat CRAO.1,4 An updated meta-analysis demonstrated that thrombolytic therapy within 4.5 hours of symptom onset was associated with a higher likelihood of a favourable visual outcome.6 Currently several randomized trials are ongoing comparing intravenous thrombolysis with placebo in adults with CRAO (THEIA, REVISION and Ten-CRAOS studies) and hopefully will provide more evidence for the practice.1
Importantly, CRAO is also a warning sign for future cerebro- and cardiovascular attacks. CRAO is commonly associated with critical internal carotid artery stenosis, which may be present in up to 40% of patients. Other traditional stroke risk factors are also prevalent.7 Therefore CRAO patients should receive an urgent and comprehensive etiological workup as do patients with cerebral stroke to initiate appropriate secondary prevention and to determine concurrent disease that requires urgent interventions (such as carotid artery stenosis).
- Mac Grory B, Schrag M, Biousse V, et al. American Heart Association Stroke Council; Council on Arteriosclerosis, Thrombosis and Vascular Biology; Council on Hypertension; and Council on Peripheral Vascular Disease. Management of Central Retinal Artery Occlusion: A Scientific Statement From the American Heart Association. Stroke. 2021;52(6):e282-e294.
- Schrag M, Youn T, Schindler J, Kirshner H, Greer D. Intravenous Fibrinolytic Therapy in Central Retinal Artery Occlusion: A Patient-Level Meta-analysis. JAMA Neurol. 2015 Oct;72(10):1148-54.
- Tobalem S, Schutz JS, Chronopoulos A. Central retinal artery occlusion – rethinking retinal survival time. BMC Ophthalmol. 2018;18(1):101.
- Hoyer C, Kahlert C, Güney R, et al. Central retinal artery occlusion as a neuro-ophthalmological emergency: the need to raise public awareness. Eur J Neurol. 2021 Jun;28(6):2111-2114.
- Fraser SG, Adams W. Interventions for acute non-arteritic central retinal artery occlusion. Cochrane Database Syst Rev. 2009 Jan 21;2009(1):CD001989.
- Mac Grory B, Nackenoff A, Poli S, et al. Intravenous Fibrinolysis for Central Retinal Artery Occlusion: A Cohort Study and Updated Patient-Level Meta-Analysis. Stroke. 2020 Jul;51(7):2018-2025.
- Callizo J, Feltgen N, Pantenburg S, et al;. European Assessment Group for Lysis in the Eye. Cardiovascular Risk Factors in Central Retinal Artery Occlusion: Results of a Prospective and Standardized Medical Examination. Ophthalmology. 2015 Sep;122(9):1881-8.