Retinal Vessel Occlusion

The sensory membrane present in the inner surface of the eyeball back is known as the retina. The retina is a membrane made up of numerous layers. One of these layers includes specialised cells called photoreceptors. Rods and cones are the two types of photoreceptors present in the retina of the human eye. 

The retina is a part of the human eye that requires regular examination as it can be prone to numerous retinal disorders. Macular degeneration, Macular oedema, Diabetic retinopathy, Hypertensive retinopathy, Detached retina, Solar retinopathy, and Central serous retinopathy are some of the common disorders of the retina. Another common disorder of the retina is Retinal Vein Occlusion (RVO). 

Retinal Vein Occlusion

Retinal Vein Occlusion is an eye disorder or to be more specific it is a retinal disorder. The retina present in the eyes is a light-sensitive tissue membrane. The specialised cells of retina- rods and cones produce neural signals by converting light. The brain then receives these signals. Hence, the retina is a membrane of utmost importance.  

The blood vessels- veins and arteries compose the vascular system that supplies blood to each part of the body. The transportation of blood to the eyes is also done with these veins and arteries. The retina is a membrane on the eyes that requires a constant blood supply. It is to ensure that all cells of the retina get enough oxygen and nutrients. The blood is also required to remove the waste produced by the retina. However, like every other artery or vein, it is also possible for the veins carrying blood to the retina to get blocked or have a blood clot. This situation is called occlusion. 

The occlusion can prevent the blood supply to the retina and building up in the vein. This will eventually result in preventing the retina from filtering the light properly. The improper filtering of light by the retina can lead to sudden vision loss. Here, the extent of vision loss depends on the position of occlusion. The occlusion in the retinal vein that causes problems in the vision is called Retinal Vein Occlusion. 

Retinal Vein Occlusion can be categorised into two types:

• Central Retinal Vein Occlusion (CRVO eye)- It is the type of RVO where the main retinal vein gets blocked

• Branched Retinal Vein Occlusion (BRVO)- In this condition, a small branch of the vein gets blocked

Causes of Retinal Vein Occlusion

The main cause of RVO is that the veins are too narrow. Diabetic people, people with high cholesterol levels and high blood pressure are more prone to Retinal Vein Occlusion. People with other disorders that affect blood flow can also have Retinal Occlusion. 

Some common symptoms

The symptoms of RVO range from visible to subtle. 

1. RVO causes blurring or vision loss. But, this blurring is painless. Usually, this condition happens in only one eye. Initially, the blurring is slight. But, with time the severity of blurring can increase. 
2. In some cases, people can also lose vision immediately due to Retinal Vein Occlusion. 

How is RVO diagnosed? 

Three types of diagnostic tests can be used to diagnose RVO:

1. Ophthalmoscopy: Ophthalmoscopy is a diagnostic test that uses an instrument called Ophthalmoscope. This instrument can be used to notice any changes in the retina. 
2. Optical coherence tomography (OCT): A scanning ophthalmoscope with 5 microns resolution can be used to take high-resolution images of the retina. These images are used to measure the thickness of the retina to observe the presence of oedema or swelling. 
3. Fluorescein angiography: This diagnostic test involves injecting a dye into the vein present in the arm that travels to the blood vessel of the retina. The photographs taken after this are used to take a careful look at the vessels. 

RVO treatments

Although there is no way to completely unblock the retinal veins, there are some ways to treat health issues that cause Retinal occlusion. Some treatment methods for RVO are:

1. Intravitreal injection of corticosteroid drugs: Corticosteroid drugs are injected to fight the components that are inflammatory and cause oedema. 
2. Pan-retinal photocoagulation therapy: When a person has a formation of a new blood vessel after RVO, this treatment method is used. 
3. Focal laser therapy: This method uses lasers to reduce swelling in some specific areas that are caused due to oedema. 
4. Intravitreal injection of anti-vascular endothelial growth factor (VEGF) drugs: The VEGF drugs have been injected that target VEGF that causes macular oedema. 

Conclusion

Retinal vein occlusion is a type of retinal occlusion which results in blurring of vision or complete loss of vision due to occlusion or blockage in the retinal vein. This type of occlusion is of two types- CRVO eye and BRVO. In CRVO the main retinal vein gets blocked, whereas in BRVO a branch of the retinal vein gets blocked. Unfortunately, no certain treatment method has been yet developed for RVO. But, there are some methods used to treat the conditions that cause RVO.