Retinal Vascular Disorders

Retinal vascular disorders refer to a range of eye diseases that affect the blood vessels in the retina and the eye. These conditions are linked to vascular diseases in the rest of the body, such as high blood pressure, high cholesterol and diabetes – conditions that cause atherosclerosis (thickening of the artery walls) and narrowing of blood vessels.

The most common retinal vascular disorders are: 

• Diabetic Retinopathy – Read more about Diabetic Retinopathy here
• Hypertensive Retinopathy
• Retinal Vein Occlusion (RVO)
• Retinal Artery Occlusion (RAO)
  
  

Hypertensive Retinopathy
High blood pressure (hypertension) causes the blood vessels in the eye to narrow, leak and harden over time as these vessels are subject to continued excessive blood pressure. In some cases, this can cause the optic nerve and retina to swell and result in vision problems.

Retinal Vein Occlusion
Retinal vein occlusion (RVO) is a common vascular disorder where the vein becomes narrowed and blocked. RVO is one of the most frequent retinal vascular disorders, after diabetic retinopathy. There are two main types of RVO. An RVO that happens in the retinal vein at the optic nerve is called a Central Retinal Vein Occlusion (CRVO). About 90% of CRVO occurs in those aged 50 and above. An obstruction at a branch of the retinal vein is referred to as Branch Retinal Vein Occlusion (BRVO). BRVO accounts for about 30% of all vein blockages. RVO can affect vision in a few ways, including swelling in the macula (the central part of the retina crucial for sharp central vision), lack of blood flow in the retina, and development of abnormal blood vessels that can cause bleeding, retinal detachment, or glaucoma.


Central Retinal Vein Occlusion (CRVO)

Retinal Artery Occlusion (RAO)
There are two main types of RAO. A central retinal artery occlusion (CRAO) is a sudden blockage of the central retinal artery – the main blood vessel that brings blood and oxygen to the eye. This is a very serious condition that requires emergency treatment. When the main source of oxygen to the eye is blocked, permanent damage and blindness often occurs. When the blockage occurs in one of the smaller branches of the central retinal artery, it is called a branch retinal artery occlusion (BRAO). Patients with RAO have a high risk of having blockage of other arteries in the brain, which can cause a stroke.

Central Retinal Artery Occlusion (CRAO)

Hypertensive Retinopathy symptoms
Most cases of hypertensive retinopathy do not result in any symptoms. In a few severe cases, there may be vision loss or headaches.

Retinal Vein Occlusion (RVO) symptoms
The obstruction to the blood flow caused by an RVO, as well as associated complications such as macular swelling, may cause blurring of vision or visual loss. These symptoms range from mild to severe and can either occur suddenly or gradually over time. Bleeding from abnormal new vessels can cause floaters or blurring of vision. If glaucoma develops due to RVO, there might be pain and blindness in the affected eye. Because of the threat to vision, regular eye examinations are important to pick up the problem early.

Retinal Artery Occlusion (RAO) symptoms
CRAO presents as a sudden, complete loss of vision in the affected eye. BRAO usually causes sudden loss of vision in part of the field of vision.

What are the risk factors?
Risk factors for Hypertensive Retinopathy
Risk factors for hypertensive retinopathy include chronic hypertension or high blood pressure, especially if the condition is not well controlled. ​

Risk factors for Retinal Vein Occlusion (RVO)
Risk factors for RVO include:

• Older age
• Hypertension or high blood pressure
• Diabetes mellitus
• High cholesterol
• Cardiovascular disease
• Cigarette smoking
• Bleeding or clotting disorders
• Vasculitis and autoimmune disorders
• Use of oral contraceptive pills
  
  

Risk factors for Retinal Artery Occlusion (RAO)
Risks factors for RAO include smoking, hypertension, high cholesterol, diabetes, coronary heart disease and a history of stroke. About 75% of CRAO cases occur in those with hypertension or blocked arteries in the heart.

When you see an ophthalmologist for assessment and diagnosis of retinal vascular disorders, you will have eye drops administered to enlarge (dilate) the pupils temporarily so that they can examine the retina and macula.

Sometimes, in addition to clinical examination, your ophthalmologist may order additional tests and evaluations, such as:

• Fundus Fluorescein Angiogram (FFA)
  In this test, a fluorescent dye is injected into a vein in your arm. Over the next few minutes, photographs are taken of the blood vessels in your eye as the dye passes through. This helps to highlight abnormal or "leaky" blood vessels, or areas of the retina where blood flow is insufficient. Uncommonly, complications due to the injection can arise, such as nausea, or in very rare cases, severe allergic reactions or heart problems.
  
  
• Optical Coherence Tomography (OCT)
  OCT is similar to an ultrasound scan, except that the latter uses sound waves to capture images. OCT uses light waves instead, and can capture very detailed, cross-sectional images of the retina and macula. OCT is a good method for assessment of swelling in the retina or macula. OCT imaging is very fast and convenient. You will be asked to place your head on a chin rest and hold still for several seconds while the images are obtained. The light beam used is painless, and unlike X-rays, does not involve any radiation.
   
• Optical Coherence Tomography Angiography (OCT-A)
  In some cases, the blood vessels in the retina can be examined with OCT-A. Based on the same technology as OCT, OCT-A uses light waves to capture very detailed images of blood vessels in the eye. OCT-A does not require any fluorescent dye injection, and also does not involve any radiation.
  
  

Treatment for Hypertensive Retinopathy
The major aim of treatment is to prevent and limit damage to the eye and other organs by addressing the root cause – hypertension – through medication and lifestyle changes.

Treatments for Retinal Vein Occlusion (RVO)
RVO is usually treated in two ways. The first is to identify and treat any underlying medical problems that cause the condition.

The second is to prevent and treat any complications from RVO in the eye. In cases where retinal blood flow is poor, laser may be required to prevent the growth of abnormal blood vessels, which can cause bleeding, retinal detachment and glaucoma. In some cases where there is swelling of the macula affecting vision, regular injections of medications into the eye, called intravitreal injections with anti-VEGF (anti-vascular endothelial growth factor) medications. Bevacizumab (Avastin), ranibizumab (Lucentis) and aflibercept (Eylea) are some medications that are frequently used. Other new medications are also in development, and may be available soon. These treatments can reduce the macular swelling and improve vision. Often, multiple injections at intervals of one month or longer are required to resolve the swelling. Repeated injections at longer intervals may also be required to maintain the visual improvement.

Treatment for Retinal Artery Occlusion (RAO)
RAO is treated in two stages. Because permanent vision loss can occur very quickly with RAO, the first step is rapid diagnosis and treatment to try and restore blood flow in the eye, by lowering the eye pressure with ocular massage, medications, and sometimes drawing fluid out from the eye. Prompt treatment may improve the chance of recovering vision, but even with treatment, the risk of blindness after RAO is high, with only about one in four patients able to retain useful vision in the affected eye. The second stage of treatment is to find out the root cause for the condition. This is important because blood vessel problems that lead to RAO can also lead to blockage of blood vessels in the brain and stroke. Early diagnosis and treatment of such vascular problems can help to prevent stroke.