ADD-ONS / OTHER VASCULAR DISORDERS
Central retinal artery occlusion (CRAO)
Created 26/04/2022, last revision 01/06/2023
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- the central retinal artery (CRA) is a branch of the ophthalmic artery (OA)
- CRA is divided into superior and inferior branches, which are further divided into nasal and temporal branches
- in approx. 50% of the patients a cilioretinal artery is present, which sufficiently supplies the macula even in case of CRAO !!
- visual impairment depends on the extent to which the artery supplies the retina; central vision may be preserved
- occlusion of the CRA typically leads to acute retinal ischemia with optic nerve edema and necrosis of the optic nerve cells ⇒ severe and permanent visual impairment
- significant spontaneous improvement occurs in <10% of patients
- the incidence is reported to be 0.85/100,000, but the true numbers are probably higher
Etiopathogenesis
Etiology
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Occlusion localization
- central retinal artery occlusion (CRAO)
- trunk occlusion leads to complete blindness
- exclude OA occlusion
- branch retinal artery occlusion (BRAO)
- occlusion of either branch results in visual field loss in the corresponding sector
Clinical presentation
- sudden onset, painless, monocular, severe visual disturbance
- patients with a patent cilioretinal artery may have only mild visual impairment
- with conservative therapy (without thrombolysis), vision in the affected eye improves in approximately 15% of patients
- occlusion may be transient, presenting as a transient ischemic attack (amaurosis fugax)
Diagnostic evaluation
Ophthalmologic examination
- clinical examination with quantification of visual impairment
- best corrected visual acuity (BCVA)
- reaction to light, motion, counting fingers, etc.
Ophthalmoscopy
- affected part of the retina is pale; the inner retinal layer is absent in the macula, and the choroidal vasculature shines through (cherry-red spot)
- arteries are narrow, filiform, with interrupted blood column
- embolic material may be visible
- ischemic retinal edema resolves within a few weeks, followed by atrophy of the retina and optic disc
Retinal fluorescein angiography (FAG) 
- a technique used to examine the circulation of the retina and choroid (parts of the fundus) using a fluorescent dye and a special camera
- detects impaired filling of retinal arteries (delay > 11s or complete absence)
- normal filling of choroidal arteries (complete filling within 5s)
- consider OA occlusion if chorioretinal filling failure is detected
- FAG can assess the effect of recanalization therapy
Electroretinography (ERG)
Etiologic evaluation
- rule out the arteritic form! (→ temporal arteritis)
- investigate vascular risk factors and exclude significant ICA stenosis
Blood tests (vascular risk factors)
- CBC, coagulation tests
- erythrocyte sedimentation rate (ESR), CRP
- ionogram, lipid panel, glycemia
- blood cultures (if endocarditis is suspected)
Vascular imaging
- neurosonology / MRA / CTA
- exclude extra-intracranial ICA stenosis
Neuroimaging
- MR-DWI is the best method to exclude clinically silent infarcts
- prior to IVT administration, it is better to perform brain CT or MRI (according to local stroke protocol)
Other tests
- ECG
- echocardiography (TTE+TEE)
- TCCD bubble test
Management
- spontaneous improvement is rare (< 10-15% of CRAOs)
- none of the conservative treatments (antiplatelet agents, intraocular pressure reduction, vasodilators, eye massage, hemodilution, steroids, heparin) have been proven effective; their use is based on case reports and small series of patients
- intravenous thrombolysis has become the standard of care in eligible patients
- a fundoscopic examination is essential before starting therapy to confirm the diagnosis and to exclude e.g. intraocular hemorrhage. If arteritis is suspected, ESR and CRP should be measured (safety of thrombolysis in the arteritic form of CRAO is unknown; in addition, immediate corticotherapy is indicated to prevent occlusion in the fellow eye)
- therapeutic window
- experimental data indicate that retinal cells survive for approx. 120-240 minutes in the presence of absolute ischemia
- even with CRA occlusion, complete ischemia rarely occurs; therefore, an interval of 0-12 hours is often used
Conservative treatment
Methods are usually combined, the effect is uncertain, trials have shown no effect compared to placebo [Fraser, 2009]
- mechanical dislodgement of the embolus (repeated bulb massage/ compression)
- vasodilation (IV pentoxifylline, sublingual isosorbide dinitrate)
- intraocular pressure reduction (attempt to increase perfusion pressure in the CRA)
- acetazolamide 500mg IV or PO
- short-term IV mannitol
- Solumedrol
- anterior chamber paracentesis
- increase blood O2
- oxygen therapy or hyperbaric oxygen therapy (HBOT) within 2-12h of onset
Intravenous thrombolysis
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Intraarterial thrombolysis
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Secondary prevention
- investigate etiology ASAP ⇒ start individualized stroke prevention (the same as for other types of stroke → see here)
- always rule out carotid stenosis, as early CEA may significantly reduce the risk of recurrent stroke
