Retinal Vascular or Arterial Occlusion

Definition

Retinal vascular or arterial occlusion is a blockage of the blood vessels in the retina, which can lead to sudden, painless vision loss. The condition can affect the central retinal artery (central retinal artery occlusion, CRAO) or the retinal veins (central retinal vein occlusion, CRVO).

Aetiology

Retinal vascular occlusions can be caused by:

Atherosclerosis
Emboli from the carotid arteries or heart
Thrombosis
Vasculitis (e.g., giant cell arteritis)
Hypercoagulable states

Pathophysiology

The blockage of blood flow in the retinal arteries or veins leads to ischaemia and subsequent damage to retinal tissues. In CRAO, the central retinal artery is occluded, often by an embolus, leading to a severe reduction in blood supply to the retina. In CRVO, the central retinal vein is blocked, often due to thrombus formation, causing increased venous pressure, haemorrhage, and oedema.

Risk Factors

Atherosclerosis
Hypertension
Diabetes mellitus
Hyperlipidaemia
Smoking
Cardiovascular diseases
Age (older adults)
Hypercoagulable states

Signs and Symptoms

Common signs and symptoms of retinal vascular occlusion include:

Sudden, painless loss of vision in one eye
Visual field defects
Flashes of light (photopsia)
Floaters

Investigations

Clinical history and physical examination
Fundoscopy to examine the retina
Fluorescein angiography to assess retinal blood flow
Optical coherence tomography (OCT) to evaluate retinal thickness and oedema
Blood tests to check for underlying systemic conditions (e.g., hyperlipidaemia, diabetes, inflammatory markers)
Carotid ultrasonography to assess for carotid artery disease
Echocardiography to identify cardiac sources of emboli

Management

Primary Care Management

Immediate referral to an ophthalmologist: Retinal vascular occlusion is an ocular emergency
Initial management:
- Ocular massage: To dislodge the embolus
- Reduction of intraocular pressure: Using medications such as acetazolamide or timolol
- Systemic management: Addressing underlying cardiovascular risk factors (e.g., blood pressure control, diabetes management)

Specialist Management

Laser photocoagulation: For treating neovascularisation and reducing the risk of complications
Intravitreal injections: Anti-VEGF agents (e.g., ranibizumab, aflibercept) or corticosteroids for macular oedema
Thrombolytic therapy: In selected cases of CRAO, though its efficacy is controversial
Management of underlying conditions: Such as anticoagulation for hypercoagulable states or carotid endarterectomy for significant carotid artery stenosis
Regular follow-up to monitor for complications and assess response to treatment

References

NICE. (2024). Retinal Vascular Occlusion: Diagnosis and Management. Retrieved from NICE
NHS. (2023). Retinal Vascular Occlusion. Retrieved from NHS
British Medical Journal (BMJ). (2022). Retinal Vascular Occlusion: Diagnosis and Management. Retrieved from BMJ
American Academy of Ophthalmology (AAO). (2021). Clinical Practice Guidelines: Retinal Vascular Occlusion. Retrieved from AAO