What is Hyperbaric Treatment of Central Retinal Artery Occlusion?
Central Retinal Artery Occlusion (CRAO) is a relatively rare and potentially harmful condition that affects the eye. Individuals suffering from CRAO suddenly lose vision in one eye without any accompanying pain. The outlook for regaining vision is generally not good. Until recently, no treatment options were available to restore at least some level of vision to the affected eye.
The retina, which is the part of the eye that receives light and sends images to your brain, uses more oxygen than any other body organ. It cannot function well without adequate oxygen.
In 2006, a new treatment option was approved, known as hyperbaric oxygen therapy. This treatment increases the amount of oxygen your blood can carry and can help treat CRAO. However, it’s not often used, partly because many eye doctors are not aware of this treatment or do not have access to the necessary equipment. It’s important to know that this option is available, as CRAO is a serious eye condition that can lead to permanent vision loss.
What Causes Hyperbaric Treatment of Central Retinal Artery Occlusion?
People who are at a higher risk of developing a blockage in the central artery of the retina include those who have giant cell arteritis (an inflammation of the lining of your arteries), atherosclerosis (hardening of the arteries), thromboembolic disease (a condition in which a blood clot forms in a blood vessel and restricts blood flow), or vasospasm (a sudden constriction of a blood vessel that reduces blood flow).
The eye gets its blood supply from the ophthalmic artery, which is a branch of the artery in the cavernous part of the internal carotid artery. The central retinal artery goes into the eye along with the optic nerve and provides blood to the inner layers of the retina through its many branches.
Between 15% to 30% of people have a cilioretinal artery, part of the blood supply that comes from the choroid (the layer of blood vessels and connective tissue between the white of the eye and the retina). This artery provides blood to the area of the retina around the macula which is responsible for central vision. Those who have a cilioretinal artery can still see from the center of their eyes because this part of the retina still gets blood.
When the central retinal artery is blocked, the inner layers of the retina that would normally get blood from the retinal circulation die out, causing vision loss. However, those layers might still get enough oxygen from the blood supply of the choroid to survive if the patient is exposed to higher concentrations of oxygen. Usually, the choroid provides most of the oxygen to the retina.
Risk Factors and Frequency for Hyperbaric Treatment of Central Retinal Artery Occlusion
Central Retinal Artery Occlusion (CRAO) is more common in males and typically affects people aged between 60-65. The incidence rate is about 1 in 50,000 to 100,000 people.
- CRAO can be caused by several conditions, with giant cell arteritis being the most common. Lupus, polyarteritis nodosa, and other types of vasculitis can also lead to CRAO.
- However, non-inflammatory conditions cause most cases of CRAO, accounting for around 90%.
- Retinal artery occlusion, often related to carotid artery disease, is the most common non-inflammatory cause and is responsible for about 70% of these cases.
- Other non- inflammatory causes include emboli (like those from atrial fibrillation), blood clotting disorders, blood cancers, and sickle cell anemia.
CRAO is a rare but urgent eye condition. It can cause sudden, painless vision loss in one eye. People with this condition often have such severe vision loss that they can only count fingers or perceive light. If no light can even be perceived, the condition might be due to obstruction of the ophthalmic artery, which leads to permanent and severe vision loss. In such cases, Hyperbaric Oxygen (HBO2) treatment would not be useful because it won’t help to restore retinal viability. However, these patients might benefit from treatments that break up clots (thrombolysis).
Signs and Symptoms of Hyperbaric Treatment of Central Retinal Artery Occlusion
Central Retinal Artery Occlusion (CRAO) typically manifests as a sudden, painless loss of vision. In many instances, there is only a perception of light, the ability to detect hand motion or count fingers, and the clarity of vision is usually poorer than 20/200.
When a patient cannot perceive light, it may suggest an occlusion of the ophthalmic artery, meaning that no blood is reaching the vessels in the choroid of the eye.
In scenarios where the primary, central vision is unaffected and an examination of the back of the eye aligns with CRAO, the patient likely has a blood supply from the cilioretinal artery. The examination may reveal a pale, yellowing of the retina due to lack of oxygen. Sometimes, a cherry-red spot may be visible in the macula area, though this is not always the case or a reliable symptom. If present, this red spot is often linked to worse outcomes.
Testing for Hyperbaric Treatment of Central Retinal Artery Occlusion
A “stroke of the eye,” similar to a stroke or a heart attack, requires urgent treatment. As soon as possible, you should be given oxygen through a “non-rebreather” mask, which delivers high levels of oxygen. At the same time, a doctor should examine the back of your eye with a tool called a fundoscope. This observation should also be recorded for further reference. It’s necessary to get an eye specialist on board, particularly one who specializes in the retina – the layer at the back of the eye.
If you experience pain, a history of eye injury, seeing sudden flashes of light or floating objects (‘flashers’ or ‘floaters’), or if you’re younger than 40, your symptoms could more likely indicate an eye injury, a detached retina, or bleeding in the vitreous (a clear, gel-like substance that fills the inside of your eye). These symptoms often make it less likely that you’re dealing with a “central retinal artery occlusion,” a condition where one of the main arteries to your eye’s retina gets blocked.
Treatment Options for Hyperbaric Treatment of Central Retinal Artery Occlusion
If you are experiencing a sudden loss of vision, it’s critical to take immediate steps for medical treatment. Here’s a simplified breakdown of a general treatment plan.
Firstly, you will be provided oxygen to breathe that’s rich in concentration. Don’t worry, this is just to help increase the amount of oxygen in your blood. During this time, an eye specialist may also be called to have a look at your condition. However, the treatment won’t be paused if the specialist isn’t immediately available.
A baseline set of tests, including a complete blood count and a check of your inflammation markers, will be conducted. In addition, a test called an ECG will be done to check the functioning of your heart.
Some additional tests could be performed later to get more information about your condition. These include an ultrasound scan of your neck artery, an MRI, and a scan of your heart known as an echocardiogram. While these tests are important, they aren’t urgent and won’t be performed immediately.
If your symptoms have appeared within the last 24 hours and you don’t respond to the high-concentrated oxygen after 15 minutes, you may be referred for a special type of treatment known as hyperbaric oxygen therapy.
Hyperbaric oxygen therapy involves breathing in 100% oxygen in a pressurized chamber. It’s typically used for conditions where tissues need more oxygen to heal, such as a blockage in the main artery of your retina (central retinal artery occlusion). This treatment protocol involves some steps where the pressure and oxygen levels are increased to see if your vision improves. If there’s no improvement, some other treatment options could be considered.
Another test known as fluorescein angiography might be conducted. This test uses a special dye and camera to illuminate the blood vessels in the back of the eye to check for any abnormalities.
This might sound complicated, but remember that your healthcare team will guide you through each step to ensure you understand what’s happening.
What else can Hyperbaric Treatment of Central Retinal Artery Occlusion be?
If you suddenly lose your vision and it doesn’t hurt (a condition known as acute painless vision loss), your doctor will consider several possible causes, which include:
- Central retinal vein occlusion (a blockage of the main vein in your retina, the part of your eye that senses light)
- Vitreous hemorrhage (bleeding into the clear gel that fills the space between the lens and the retina)
- Retinal detachment (a situation where the retina detaches from the back of the eye)
- Posterior circulation stroke (a stroke that occurs in the part of the brain that’s connected to your eyes)
- Ischemic optic neuropathy (damage to the optic nerve due to insufficient blood supply)
- Amaurosis fugax (a temporary loss of vision in one eye caused by decreased blood flow)
These conditions are considered when identifying the cause of acute painless vision loss.
What to expect with Hyperbaric Treatment of Central Retinal Artery Occlusion
If patients are treated with oxygen therapy within 8 hours of experiencing symptoms, they have an 83% chance of significantly improving their vision. This improvement is equal to or better than a 3-line improvement on the Snellen eye chart, a common tool for testing visual acuity.
An investigation involving 39 patients, who suffered from Central Retinal Artery Occlusion (CRAO), showed that 72% of the patients had improved vision. The improvement averaged at 5 lines better on a modified version of the Snellen eye chart.
Possible Complications When Diagnosed with Hyperbaric Treatment of Central Retinal Artery Occlusion
After a Central Retinal Artery Occlusion (CRAO), especially in people with diabetes, it is possible to develop new blood vessels in the eye. This event, known as neovascularization, can have serious consequences. It may lead to continued loss of vision, an eye condition called neovascular glaucoma, and bleeding within the jelly-like substance that fills the eye, known as vitreous hemorrhage. These problems can occur even if the original vision loss from the CRAO is successfully treated with hyperbaric oxygen therapy (HBO2). Currently, it is still uncertain whether HBO2 treatment has any impact on this neovascularization process.
Generally, people tolerate HBO2 treatment quite well. However, some might experience issues such as feeling restless or anxious in a confined space, and a condition known as otic barotrauma, which is damage to the ear due to changes in atmospheric pressure. Other complications linked to this treatment are quite rare.
Common Side Effects:
- Continued loss of vision
- Neovascular glaucoma
- Vitreous hemorrhage
- Feeling anxious in a confined space
- Otic barotrauma
Preventing Hyperbaric Treatment of Central Retinal Artery Occlusion
If you suddenly lose your vision, it’s crucial that you seek medical help immediately. This is because the amount of vision that can be saved or restored in a condition known as ‘central retinal artery occlusion’ (CRAO) is heavily reliant on how fast treatment is started. The suggested treatment usually includes HBO2, a type of oxygen therapy, and possibly thrombolytics, medication used to dissolve blood clots. Therefore, those at risk of CRAO need to be aware of this and go straight to the emergency department if they experience sudden vision loss.
