What is Central Retinal Artery Occlusion?
Central Retinal Artery Occlusion (CRAO) is a critical eye condition arising from the sudden blockage of the central retinal artery, disrupting blood flow to the retina. It is easiest to imagine CRAO as the equivalent of a “stroke” but in your eye.
This page explains the causes, symptoms, and treatment options for CRAO. If you are suffering any of the symptoms described on this page, it is advised that you urgently seek a full vitreoretinal examination with us or with a retina specialist.
What are the symptoms of Central Retinal Artery Occlusion?
The following are the most common and important symptoms of an acute Central Retinal Artery Occlusion:
- Sudden Vision Loss: if you notice an sudden drop in your vision then this may be a sign of CRAO
- Blurred or Diminished Vision: you may not experience sudden vision loss, however, blurring of vision or a general degradation usually in a very short period of time can be a sign of CRAO.
- Visual Field Defects: CRAO may also manifest in the reduction or a distorting of your visual field i.e. the area of vision that you have.
What are the treatment options for Central Retinal Artery Occlusion:
There are several treatment options to treat CRAO when it first occurs:
- Ocular Massage: your doctor will rub their thumb over the affected eye which is closed to try and physically dislodge the clot
- Thrombolytic Medications: blood-thinning medications may be prescribed to try and increase blood flow around the clot and to dislodge it
There are also treatments which can be used for longer-term complications of CRAO such as Cystoid Macular Oedema (CMO) or neovascularisation. These include:
- Intravitreal injections of Anti-VEGF agents
- Pan-retinal Photocoagulation
- Sub-threshold laser
All of the above treatment options are available at The Retina Clinic London as required. Prof. Stanga and his team will always develop a personalised treatment plan according to your symptoms and needs.
How effective are treatments for Central Retinal Artery Occlusion?
Understanding the prognosis of Central Retinal Artery Occlusion (CRAO) involves recognizing the variability in outcomes based on several factors.
The following factors will affect your rate of visual recovery:
1) Extent of Ischemia:
The severity and duration of reduced blood flow to the retina play a significant role in visual recovery. In cases of milder ischemia, some patients may experience partial or even near-complete visual improvement.
2) Time of Intervention:
Timely medical intervention, such as ocular massage, thrombolytic therapy, or hyperbaric oxygen treatment, can positively influence visual outcomes. Swift action within hours of symptom onset may enhance the chances of preserving vision.
3) Underlying Health Conditions:
The presence of underlying health conditions, such as hypertension or diabetes, can impact the overall prognosis.
Effective management of these conditions contributes to better long-term outcomes.
What can cause Central Retinal Artery Occlusion?
There are several different causes which can be attributed to Central Retinal Artery Occlusion, which include:
Atherosclerosis
Atherosclerosis involves the gradual accumulation of fatty deposits, known as plaques, within the walls of arteries, including those supplying the retina.
The buildup of these plaques narrows the central retinal artery, compromising blood flow to the retina. Over time, this can contribute to the onset of CRAO.
The following are risk factors for atherosclerosis and higher levels of any of these or combinations are indicators for a higher chance of having this condition:
- Age
- Hypertension
- High cholesterol levels
- Smoking
- Diabetes
Blood Clots
Blood clots, or thrombi, can form due to various cardiovascular conditions, posing a risk to the circulatory system.
When a blood clot obstructs the central retinal artery, it hampers the normal blood supply to the retina, leading to the sudden vision loss characteristic of CRAO.
The following are risk factors for blood clots and presence of any of these risk factors are indicators for a higher chance of having this condition:
- Atrial fibrillation
- Hyper-coagulable disorders
- Cardiovascular diseases
Embolism
Emboli are tiny particles that can travel through the bloodstream. They originate from various sources, such as the heart or large arteries, and when these particles reach smaller vessels like the central retinal artery, they can create obstructions.
Emboli play a significant role in the development of Central Retinal Artery Occlusion (CRAO). When an embolus becomes lodged in the central retinal artery, it disrupts the normal blood flow to the retina. This sudden blockage can lead to ischaemia (lack of blood supply) in the retina, resulting in vision loss.
Types of Emboli
1) Cholesterol Emboli
- Source: Typically originates from cholesterol plaques in large arteries.
- Characteristics: Small, yellowish particles.
- Risk Factors: Atherosclerosis, vascular disease.
- Effect on CRAO: Lodging in the central retinal artery, causing a sudden reduction in blood flow.
2) Platelet Emboli:
- Source: Formation of clumps of platelets.
- Characteristics: Composed mainly of platelets and fibrin.
- Risk Factors: Conditions promoting excessive clotting.
- Effect on CRAO: These emboli can migrate and obstruct the retinal artery, leading to CRAO symptoms.
Reducing the risk of embolic CRAO involves managing underlying conditions contributing to embolism formation. This may include lifestyle modifications, medication management, and close monitoring of cardiovascular health.
Inflammatory Diseases
Inflammatory conditions affecting blood vessels, such as giant cell arteritis, can lead to significant vascular changes. This inflammation within the blood vessels can narrow or block the central retinal artery, triggering CRAO.
The following are risk factors for inflammatory conditions:
- Autoimmune diseases
- Giant cell arteritis
- Vasculitis
How is Central Retinal Artery Occlusion diagnosed at The Retina Clinic London?
At The Retina Clinic London, if you present with any of the symptoms described here, you will undergo a full Vitreoretinal examination led by Prof. Stanga and his medical team. It will involved the following tests to ascertain whether an arterial occlusion is ongoing:
- Extensive medical history taking to understand if you have any of the major risk factors for CRAO as previously described
- Your visual acuity will be measured to see how much your vision has dropped
- Multi-wavelength Ultra-wide field Colour Fundus Imaging: images of the back of your eye where the retina is will be taken which allow for up to 80% of the retina to be visualised in one picture. These images will allow Prof. Stanga and his team to assess the extent of any occlusion including whether there is any residual haemorrhage throughout the retina.
- Optical Coherence Tomography (OCT): Cross-sectional scans will be acquired following the fundus imaging to look at the layers of the retina and to see whether there is any haemorrhage of blood in the layers of the retina which will require treatment.
- Fluorescein Angiography: following all of the previous testing, Prof. Stanga and his team may request that you undergo a Fundus Fluorescein Angiography, which involves injecting a vegetable die into your body and imaging it with a special light wavelength, which will allow them to ascertain any damage to the blood vessels in retina, if there is any ischaemia or areas or retina lacking blood supply, and whether you are developing neovascularisation or abnormal blood vessels which grow in response to a lack of blood supply.