25th December 2023

Vascular disease

This may be divided into retinal artery occlusion (central/branch retinal artery occlusion) and retinal vein occlusion  (central/branch retinal vein occlusion).

Central retinal artery occlusion (CRAO):

CRAO is the sudden blockage of the central retinal artery, resulting in retinal ischaemia and rapid vision loss. The central retinal artery is the first intra-orbital branch of the ophthalmic artery. Occlusion of the central retinal artery results in retinal ischemia, necrosis and vision loss. Sources of occlusion include:

Embolic:

• Cholesterol (Hollenhorst) plaque: carotid vascular disease
• Platelet-fibrin: thrombo-embolism
• Calcific: cardiac valvular disease

Thrombotic:

• Atherosclerotic disease
• Collagen vascular disease
• Vasculitis: giant cell arteritis

Associations of CRAO:

• Hypertension
• Diabetes mellitus
• Carotid artery disease
• Collagen vascular disease
• Vasculitis
• Trauma
• Coagulopathy

Clinical Presentation:

CRAO typically presents with sudden, painless, monocular vision loss that occurs over seconds. Patients may report an antecedent transient visual loss (amaurosis fugax). Visual acuity is often drastically reduced (VA <6/60). A relative afferent pupillary defect (RAPD) will be present. Fundus examination reveals retinal pallor with a ‘cherry red’ spot at the fovea. At 4-6 weeks, the pale optic disc appears pale, and retinal arterioles are attenuated.

Investigations:

Investigations are aimed at identifying the underlying cause. Inflammatory markers (FBC, CRP, ESR) are mandatory to exclude giant cell arteritis (GCA). Further specific testing, including thrombophilia, autoimmune and infective screening, is directed by concomitant symptoms. A fast-track referral to stroke clinic is recommended to identify thrombo-embolic sources (ECG, ECHO, carotid Doppler).

Management:

There are no established treatments to restore vision following CRAO. Various treatments have been described to restore perfusion to the retina if within 24 hours of onset:

• Ocular massage to dislodge emboli
• Reduction of intraocular pressure with intravenous acetazolamide or anterior chamber paracentesis
• Supplemental oxygen

Fibrinolysis may be beneficial within 4.5 hours of symptom onset. A CT head should be obtained to rule out intracranial haemorrhage.

In cases of suspected GCA, immediate corticosteroids are required to protect the contralateral eye (see section below on GCA). If thrombo-embolic disease is suspected, secondary prevention should be started with clopidogrel 300mg OD followed by 75mg to continue, and atorvastatin 80mg OD pending referral to stroke/TIA clinic.

Prognosis:

Vision loss is usually irreversible. There is a small risk of neovascular disease in the long-term, although patients often do not require long-term surveillance.

Branch retinal artery occlusion

Branch retinal artery occlusion is usually the result of an embolus that lodges at the bifurcation of a retinal arteriole. The retinal and visual changes relate only to the part of the artery occluded. Vasculitis (GCA), in this instance, is extremely rare, and in the absence of associated symptoms, no workup for giant cell arteritis is required. Patients should be referred for further investigations as per TIA. There are no treatments.

Retinal vein occlusion

There are two types of RVO: Central retinal vein occlusion (CRVO) and Branch retinal vein occlusion (BRVO). In CRVO, structural changes in the central retinal artery and the lamina cribrosa leads to compression of the pre-laminar central retinal vein. Subsequent turbulent flow in the central retinal vein predisposes to thrombosis. In BRVO, occlusion of a tributary retinal vein by an adjacent retinal arteriole occurs at the site of an AV crossing (both retinal arterioles and veins share a common adventitial sheath). Underlying structural changes occur as a consequence of arteriosclerosis, hypertension, diabetes mellitus and glaucoma. Thrombi may also be the result of various hyperviscosity syndromes.

The mechanism of visual loss is due to the development of retinal ischaemia and macula oedema.

Associations of CRVO

• Hypertension
• Diabetes
• Smoking
• Obesity
• Protein S, protein C, anti-thrombin III deficiency
• Myeloma
• Antiphospholipid syndrome
• Vasculitis
• Glaucoma

CRVO can be classified into non-ischaemic and ischaemic forms, and the following clinical features can be seen in each:

Non-ischaemic:

• 80% of CRVO
• VA usually >6/60
• May be no RAPD
• Less extensive haemorrhages +/- CWS; swollen optic nerve head; macula oedema
• Better prognosis

Ischaemic:

• 20% of CRVO
• VA <6/60
• Marked RAPD
• Extensive haemorrhages and CWS; swollen optic disc
• Worse prognosis

Investigations:

The following investigations are aimed at identifying associations which require urgent action, such as severe hypertension, uncontrolled diabetes or rarely blood dyscrasias.

• Blood pressure
• FBC
• ESR & CRP
• Glucose

Further routine investigations are not recommended. However, in patients below 40 years of age or those without identifiable risk factors or unusual presentations (bilateral CRVO), further tests may be performed to exclude an underlying systemic prothrombotic disorder

• ACE
• Anti-cardioplin antibodies
• ANA
• ds-DNA
• ANCA
• Thrombophilia screen
• CXR

Management:

Anti-VEGF agents (bevacizumab) can treat macula oedema but may be of little benefit in ischaemic CRVO. Patients with retinal vein occlusions are at risk of retinal, iris and anterior chamber angle neovascularisation and may develop neovascular glaucoma at 3 months (‘100-day glaucoma’). Neovascular disease can be treated by laser photocoagulation to reduce the ischaemic drive.

Image Source: Wikimedia Commons (2019). Cherry red spot in patient with central retinal artery occlusion (CRAO), Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Cherry_red_spot_in_patient_with_central_retinal_artery_occlusion_(CRAO).jpg (Accessed on: 15  May 2022).

Image Source: Wikimedia Commons (2019). Fondo de ojo Ostrucción Vena central, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Fondo_de_ojo_Ostrucci%C3%B3n_Vena_central.png (Accessed on: 15  May 2022).