Vascular Occlusions

What is a retinal vascular occlusion?

Vascular occlusions simply refer to blocked or constricted blood vessels. These vascular occlusions can also happen in the eye and also the retina. The retina is a particularly important part of the eye, housing the special light sensitive cells that capture the light and transmit it as signals to your brain to achieve sight. As with any living part of the body, the cells in the retina require a supply of nutrients and oxygen. This supply of essentials takes place through the vascular system, where blood carries these much needed nutrients and oxygen to the retinal cells.

It is however, very possible for the blood vessels that carry blood to and from the retina to be blocked or obstructed. This can be due to a blood clot, or a variety of other reasons. This situation of a blockage is hence known as an occlusion.

This occlusion may lead to a build up of blood and other fluids in the area, or at the retina. When this happens the retina’s ability to function properly may be affected. In certain cases, the occlusion grows large enough to obstruct light that enters the eye. This results in a loss of vision. The severity of vision loss is dependent on the site of which the occlusion occurred, size of the occlusion and whether other complications have taken place.

Retinal vascular occlusions can be potentially serious. The site of the blockage causes a buildup of pressure due to the constant supply of blood to the site. Without an outlet to drain the collected blood, the blood vessel may burst and surrounding structures may be damaged. The situation can be exacerbated by bodily conditions such as atherosclerosis – a hardening of the arteries, which can further increase the risk of serious complications.

What are the different types of retinal vascular occlusion?

Retinal Vascular Occlusions mainly fall into 2 categories, and this depends on the type of blood vessel the occlusion takes place at:

Retinal artery occlusion

A retinal artery occlusion is a blockage of one of arteries that lead to, or are at the retina. Retinal arteries are blood vessels that carry blood from the heart to your retina. The blood in the arteries carry a fresh supply of oxygen from the lungs, and is important in keeping the retinal cells alive. There is a main artery that feeds into of your retina known as the central retinal artery. This then splits into smaller, branch retinal arteries as it draws closer to the retina. It is possible for an occlusion to happen at the central retina artery, or at the smaller branch retinal arteries.

Retinal vein occlusion

The other type of retinal vascular occlusion happens in a different type of blood vessels found in the retina — the retinal veins. The blood in the veins differs from arterial blood, in that the blood found in a retinal vein is deoxygenated. Having transport the oxygen it carried from the lungs into the retinal cells, the blood now carries waste from the retinal cells back to the heart, where it then goes on to various other parts of the body.

A retinal vein occlusion can happen in both the central retinal vein, or in the small branch retinal veins.

It should be noted that occlusions that happen in the main retinal vein or artery are considered more serious than occlusions that occur in the branch veins and arteries.

What are the causes of retinal vascular occlusion?

The exact cause for vascular occlusions in the retina is not clearly understood. A factor that may increase the likelihood of retinal vascular occlusions may be that the veins in the eye are simply too narrow. Other factors that affect the flow of blood in the body can increase the risk of a retinal vascular occlusion occurring. A few examples are listed below:

• atherosclerosis
• blockages of the arteries
• narrowing of the arteries
• diabetes
• blood clots – these can come from other parts of the body and cause a blockage in the blood vessels in the eye
• heart problems – arrhythmia, or valve issues
• high cholestrol
• high blood pressure
• weight problems – such as being severely overweight
• smoking
• inflammatory disorders

Symptoms of retinal vascular occlusion

The most obvious symptom of a retinal vascular occlusion is a sudden and drastic change in vision. The change can take a variety of forms such as blurry vision, partial or even complete loss of vision.

The changes in vision commonly only occur in one eye during a retinal vascular occlusion. The symptoms do not ‘spread’ to the other eye. Also, the sensation of pain is not a symptom that retinal vascular occlusions bring. If pain is involved, it may be due to a different condition.

Once a retinal vascular occlusion occurs, the symptoms can be permanent or temporary. The earlier you seek treatment, the higher chance of the symptoms being treatable and non-permanent. If you experience sudden and drastic changes to your vision, you should call your eye doctor, eye specialist or opthalmologist immediately. Seek treatment from a nearby hospital immediately, if you experience a partial or full loss of vision in eye.

Between the two types of vascular occlusions, retinal artery occlusions are catastrophic and may lead to sudden blindness in the affected eye. A retinal vein occlusion are also serious but these may be treated if detected early. The most important step of management is to control the pre-existing hypertensive, high blood pressure or high cholesterol condition in order to prevent another ‘stroke’ of the other eye, heart (heart attack) or brain stroke.

Treatment

Vein occlusions may be treated with eye injections which can improve the vision dramatically. Sometimes continuing eye injections may be necessary to maintain the good vision of the affected eye, which could be considered a small price to pay for ensuring useful vision in a ‘stroke’ eye.