Retinal Artery Occlusion
Author: Ameen Marashi, MD
Documentation of visual loss is essential, which includes the location and duration along with detailed ocular history and amaurosis fugax
It is crucial to document any signs of giant cell arteritis (GCA)  such as headache, neck pain, fever, scalp tenderness, and jaw claudication.
Take into consideration any previous ophthalmic diseases and previous ocular treatments such as topical medications, surgical interventions (cataract, refractive, etc.) laser, injections (intravitreal, retrobulbar, etc.) and medication such as Anti-VEGF, steroids or other.
Family or Medical history obtained, such as diabetes millets, systemic hypertension along with cardiovascular diseases, hyperlipidemia, collagen vascular disease, coagulopathies, thrombotic disorders, etc. along with social history such as smoking documented.
However, retinal emboli associated with smoking, hypertension, body mass index, diabetes, high lipid serum levels, and cardiac diseases, are modifiable.
A list of ocular examination should set
1) Best-corrected visual acuity (BCVA), this is an essential step which is performed by a trained optometrist or certified ophthalmologist to document the visual impairment.
BCVA can be as good as 20/20 or as bad as 20/200 and less depending on the presence of the cilioretinal artery and degree of obstruction .
2) Pupillary evolution, as large areas of retinal ischemia, may induce relative afferent pupillary defect (RAPD), which is more prominent in more complete occlusions for an extended period.
3) A slit-lamp examination done with a thorough exam of clarity and regularity of the cornea and conjunctival abnormality such injection of conjunctival vessels documented. Meticulous iris exam to rule out neovascularization is crucial, especially in cases of a relative pupillary defect.
4) Intra Ocular Pressure (IOP) documentation is essential as high IOP is associated with neovascular glaucoma, iris, or/and angle neovascularization or patient with glaucoma history.
Note when high IOP spotted a corrected IOP documented after central corneal thickness measurement.
5) Gonioscopy before dilated eye exam is essential to document anterior chamber angle status (open or closed) and to rule out neovascularization on the angle, blood in Schlemm canal and fibrovascular tissue especially in cases combined with Central Retinal Vein Occlusion (CRVO) , high IOP and ischemic retinal changes.
6) Bilateral dilated fundus exam is essential with a detailed examination of the optic disc, macula, posterior pole, a mid-peripheral, and peripheral retinal exam with specialized indirect wide-field lenses using slit-lamp biomicroscopy or indirect ophthalmoscopy.
Retinal whitening is due to retinal nerve fiber layer (RNFL) opacification from inner retinal edema induced by ischemia.
A cherry-red spot at the macula in central retinal artery occlusion (CRAO) or well-perfused macula in the presence of a cilioretinal artery in 20 % of the population. 
Retinal vascular box carrying or cattle track
The presence of hemorrhages, cotton wool spots, and venous beadings are documented as well.
Neovascularization on the optic disc or/and else-where is ruled out.
Fundus images are essential for documenting the location of retinal opacifications, ischemic changes and cherry red spot along with location and type of emboli , such as calcified which may originate from calcified heart valve or Hollenhorst plaque (platelet-fibrin-cholesterol), features boxcar (cattle track) segmentation which may arise from carotid artery , aortic arch or heart valves and to document the presence of cotton wool spots, optic disc edema, retinal vascular caliber changes, neovascularization of the disc (NVD), or/and elsewhere (NVE).
The fundus image helps to study in detail if there is a combination of CRVO, which adds dilated tortuous veins with intraretinal hemorrhages.
Optical Coherence Tomography (OCT)
Acute RAO features hyperreflectivity and thickening of inner retinal tissues ; in contrast, old RAO may present with thinning of inner retinal tissue .
OCT is a useful tool to document any preexisting macular pathologies.
OCT may show increased reflectivity in the level of deep plexuses as a result of ischemia and labeled as paracentral acute middle maculopathy , which can be an early sign of acute RAO.
OCTA accurately distinguishes retinal capillary plexuses at different planes. OCTA sensitive to evaluate the extent of ischemic macular changes; OCTA monitors vascular flow changes during RAO .
Fundus Fluorescein Angiography (FFA)
FFA features delayed filling of both artery and arteriovenous transit time (more than 11 seconds) along with arterial narrowing . However, the filling defect appears in the early phase of the angiogram, in later phases, the perfusion appears patent. In some cases of the subtotal occlusions, the artery may show partial filling, and retina may show retrograde perfusion.
FFA is useful in showing the extent and location of RAO as in cases of RAO associated with the patent cilioretinal artery; it can easily differentiate the well-perfused macula from areas that have a filling defect.
FFA documents the choroidal flow, which is helpful in ophthalmic artery occlusion, which features patches of choroidal flow . ICG excel in evaluating the choroidal circulation.
In cases of RAO combined with CRVO shows widespread capillary nonperfusion and extinction of medium-sized vessels with a leak in the macula along with dilated tortuous veins .
In cases of Ophthalmic Artery Occlusion (OAO), FFA featured both retinal and choroidal nonperfusion and delayed the filling of both circulations in addition to dilated veins without tortuosity and staining of retinal arteries. Choroidal patchy non-perfusion has seen in both OAO and GCA 
Note that the physician should obtain signed consent explaining the rare complications of FFA, including death 1/200000, and FFA facility should have an emergency plan in situ .
Diagnosing patients with RAO
In patients over the age of 50 diagnosed with symptomatic RAO evaluated for atheromatous and embolic disorders. Hence, an immediate referral to the emergency department  (Stroke center if available) strongly recommended for two reasons:
· First to rule out any associated systemic disease
· Second, a prompt workup evaluating the high risk for cerebral stroke (which can be as high as 25%) within the first four weeks or myocardial infarction assessing cardiac status.
Assessment of heart valves and carotid arteries locating the source of emboli using:
Carotid doppler ultrasonography to rule out plaque in cases of Hollenhorst plaque .
Heart echography is done to rule out valve calcification in calcific emboli .
Multislice computed tomography angiography in particular circumstances such as carotid or aortic dissection .
Magnetic resonance angiography is the gold standard to identify the degree of stenosis of carotid artery and plaque status, especially in cases of OAO .
Medical history for systemic diseases and symptoms such as paresthesias, weakness, and signs of transit ischemia obtained; family history along with social history (smoking) documented.
An ophthalmologist should search for GCA symptoms in patients over 50 years old such as headache, neck pain, fever, scalp tenderness, jaw claudication, malaise, and fatigue.
ESR (erythrocyte sedimentation rate), CRP (C-reactive protein), Platelets, and CBC (complete blood count) should be obtained immediately and scheduled for temporal artery biopsy.
In patients, 50 years old or younger assessed for autoimmune, hypercoagulable and inflammatory disorders evaluating antiphospholipid antibodies, and hypercoagulable diathesis, workup include factor V Leiden mutation; protein C&S and antithrombin III deficiencies .
Patients with asymptomatic BRAO referred to a primary care physician for cardiac vascular evaluation and to rule out a risk of ischemic stroke.
RAO associated with CRVO has a poor prognosis and indicates an active systemic disease such as autoimmune (systemic lupus erythematosus, posterior scleritis, etc.), blood dyscrasias , optic neuritis, malignancies, lymphoma, and leukemia or in the setting of retrobulbar hemorrhage and orbital inflammatory disease.
In cases of cilioretinal artery occlusion, visual prognosis is usually good in isolated cilioretinal artery occlusion and combined with CRVO (depends on the severity of CRVO) .
In cases of cilioretinal artery occlusion combined with anterior ischemic optic neuropathy prognosis is poor , features a hyperemic or pale swollen optic disc, a pale swollen optic disc is suggestive of GCA .
Systemic evaluation is the same as symptomatic RAO except for cases associated with CRVO that may not require a search for the embolic source.
The rational management of RAO is to stabilize, improve vision if possible, or/and prevent further vision loss.
Patients diagnosed with RAO subjected to emergent systemic evaluation, as mentioned above, for life-threatening condition identification. However, spontaneous resolution can occur in 22% of patients .
In cases of RAO accompanied with GCA (such as cilioretinal artery occlusion), systemic steroids recommended  preventing visual loss in the other eye or vascular occlusion elsewhere.
In acute cases of RAO, especially in the first 24 hrs. Anterior chamber paracentesis , digital massage (repeatedly every 10-15 seconds of pressure), sublingual isosorbide, or systemic acetazolamide may be helpful,  but has a controversial effect  another treatment option such as intravenous thrombolytic treatment is also controversial .
Other treatment options include hyperbaric oxygen, which can preserve retinal tissue up to 72 hrs.  Nd-YAG laser to photofragment embolus reported treating CRAO .
Anticoagulants reserved to prevent cerebral stroke and myocardial infarction in high-risk patients, along with encouraging smoke cessation and controlling underlying diseases such as diabetes, hyperlipidemia, and systemic hypertension .
When neovascularization proliferates into the anterior chamber or iris, pan-retinal laser photocoagulation 1500 to 2000 burns 500 μm spot size indicated  with or without Anti-VEGF, especially in cases with vitreous hemorrhage not to improve vision but to prevent the development of neovascular glaucoma.
Endarterectomy indicated when carotid occlusion is more than 70 % to 99% , but in cases, occlusion is 50%-70% medical therapy indicated, however, endarterectomy is not recommended in total carotid artery occlusions .
Flow chart summarizes the approach and management of retinal artery occlusion
Follow up and prognosis
Visual acuity changes and visual field loss followed up, along with the status of elevated blood pressure, hyperlipidemia, and hyperglycemia.
Slit-lamp examination at follow up include iris examination for neovascularization and gonioscopy, along with Intraocular pressure measurement and posterior pole with a peripheral retinal exam.
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These guidelines were reviewed and updated in September 2020