Retinal Vein Occlusion

Retinal vein occlusion occurs when one of the tiny veins in the retina becomes blocked by a blood clot.

What is retinal vein occlusion?

This is a serious condition, which can affect your vision, caused by a blood clot in a tiny vein in the retina (the seeing membrane in your eye). The retina is a thin, light-sensitive membrane that lines the back of your eye.

An occlusion is a medical term for blockage so retinal vein occlusion means the retinal vein is blocked. This stops blood draining away from the retina and blood ‘backs up’ behind the blockage. Fluid and blood will then leak from the blood vessels into the delicate tissue of the retina, forcing its layers apart and affecting its ability to respond to light.

Who gets retinal vein occlusion and why?

Retinal vein occlusion is a fairly common cause of loss of vision. It is most common in people over the age of 60 years.

It happens because the vein is blocked. This blockage may occur either because of pressure on the outside of the vein (usually from a retinal artery) which squashes or kinks it, or because of sludging of fatty deposits or clotting of blood inside the vein, forming a plug.

Conditions which increase the risk of retinal vein occlusion include:

  • High blood pressure.
  • High cholesterol/high lipid levels.
  • Raised pressure in the eye (glaucoma).
  • Diabetes.
  • Smoking.
  • Conditions which ‘thicken’ the blood.

Age-related macular degeneration is the most common cause of sight impairment in those aged over 50. It causes a gradual loss of central vision, which we need for for detailed work and for things like reading and driving. Edge vision (peripheral vision) is not lost.

Visual loss in age-related macular degeneration can occur within months, or over many years, depending on the type and severity. There are two main types of age-related macular degeneration – ‘wet’ and ‘dry’. ‘Wet’ age-related macular degeneration is most severe but more treatable.

Understanding the back of the eye

The retina is made up of two main layers. There is an inner layer of ‘seeing cells’ called rods and cones. These cells react to light and send electrical signals via the optic nerve to the brain. The cones help us to see in the daylight, and form colour vision. Rods help us to see in the dark. The outer layer – the retinal pigment epithelium (RPE) – is a layer of cells behind the rods and cones. The RPE helps to nourish and support the rods and cones. It acts like a filter, keeping harmful substances away from from the sensitive cells.

The macula is the small area of the retina where your central vision is formed. It is about 5 mm in diameter. The macula is the area which is the most densely packed with rods and cones. In the middle of the macula is an area called the fovea, which only contains cones. The fovea forms your pinpoint central vision.

The tiny blood vessels of the choroid bring oxygen and nutrients to the retina. Bruch’s membrane is a thin protective barrier between the choroid and the delicate retina.

When you look at an object, light from the object passes through the cornea, then the lens, and then hits the retina at the back of the eye.

What is age-related macular degeneration (AMD)?

AMD (also called AMRD) occurs when cells in the macula degenerate. Damage to the macula affects your central vision which is needed for reading, writing, driving, recognising people’s faces and doing other fine tasks.

The rest of the retina is used for peripheral vision – the ‘side’ vision which is not focused. Therefore, without a macula you can still see enough to get about, be aware of objects and people and be independent. However, the loss of central vision will severely affect normal seeing.

Who develops age-related macular degeneration (AMD)?

AMD) only develops in older people (there are other rare types of macular degeneration which occur in younger people). AMD is the most common cause of severe sight problems (visual impairment) in the developed world. It is more common with increasing age.

It is rare under the age of 60. It usually begins in one eye. About 5 in 100 people aged over 65 and about 1 in 8 people aged over 80 have AMD severe enough to cause serious visual impairment. About twice as many women over the age of 75 have AMD compared with men of the same age. People of Caucasian ethnicity are more likely to develop AMD than those of African or Asian ethnicity. It is also more common in those who smoke, those who are oveweight and those with cardiovascular disease.

What are the types of age-related macular degeneration (AMD)?

Dry AMD

This is the most common form and occurs in 9 in 10 cases. In this type the cells in the RPE of the macula gradually become thin (they ‘atrophy’) and degenerate. This layer of cells is crucial for the function of the rods and cones which then also degenerate and die. Dry AMD is a gradual process as the number of cells affected increases: it usually takes several years for vision to become seriously affected. Many people with dry AMD do not totally lose their reading vision. If only one eye is affected you may not be aware of the change in your vision, and it may be detected unexpectedly during an eye test.

Wet AMD

Wet AMD may also be called neovascular or exudative AMD. It occurs in about 1 in 10 cases. In wet AMD, in addition to the retinal pigment cells degenerating, fragile new blood vessels grow from the tiny blood vessels in the choroid into the macular part of the retina. These vessels tend to leak blood and fluid. This can damage the rods and cones and cause scarring in the macula, causing further vision loss. Wet AMD can cause distortion of your central vision, and causes severe visual loss over quite a short time – sometimes weeks or months. Very occasionally, if there is a bleed (haemorrhage), this visual loss can occur suddenly, within hours or days.

If you develop wet AMD (see below) in one eye the risk of developing wet AMD in the second eye is about 1 in 4.

Both wet and dry AMD are further classified as early, intermediate or advanced, according to the degree of damage to the macula. 6 of every 10 cases of intermediate/advanced AMD are due to wet AMD.

What causes age-related macular degeneration (AMD)?

In people with AMD the cells of the RPE stop working work so well with advancing age. They gradually fail to take enough nutrients to the rods and cones and do not clear waste materials and byproducts. As a result, tiny abnormal deposits called drusen develop under the retina. In time, the retinal pigment cells and their nearby rods and cones degenerate, stop working and die. This is the dry type of AMD.

In wet AMD, new blood vessels grow into the layers of the retina from the choroid. The reason why this happens in some cases of AMD is not known, although waste products or shortage of oxygen may be involved.

Certain risk factors increase the risk of developing AMD. These include:

  • Smoking tobacco.
  • High blood pressure.
  • A family history of AMD. (AMD is not a straightforward hereditary condition. However, your risk of developing AMD is increased if it occurs in other family members.)
  • Sunlight. Laboratory studies suggest that the retina is damaged by sunlight rays (UVA and UVB rays).
  • Being very overweight.
  • Poor diet.

AMD is more common in people from white (Caucasian) racial backgrounds than from other racial groups.

What are the symptoms of age-related macular degeneration (AMD)?

Early symptoms

AMD is painless. Symptoms of dry AMD tend to take 5-10 years to become severe. However, severe visual loss due to wet AMD can develop more quickly.

If AMD develops in one eye only, you may not be aware of it until it’s quite advanced, as the other eye will still see the things you are looking at with your central vision. When both eyes are affected you are more likely to notice symptoms.

The main early symptom is worsening of central vision despite using your usual glasses. In the early stages of the condition you may notice that you need brighter light to read by. Words in a book or newspaper may become blurred. Colours may appear less bright and you may have difficulty recognising faces and facial expressions.

Later symptoms

As the condition worsens, a ‘blind spot’ then develops in the middle of your visual field. This is not always initially noticeable. However, it tends to become larger over time as more and more rods and cones degenerate in the macula.

One early symptom of wet AMD is visual distortion. Typically, straight lines appear wavy or crooked. For example, the lines on a piece of graph paper, or the lines between tiles in a bathroom.

Visual hallucinations (also called Charles Bonnet syndrome) can occur if you have severe AMD. People see different images, from simple patterns to more detailed pictures – often they see complicated images of children or animals. The experience can be upsetting but is less frightening if you are aware that it can happen in AMD. Importantly, it does not mean you are developing a serious mental illness. If you do develop visual hallucinations they typically improve by 18 months.

Peripheral vision is not affected with AMD and so it does not cause total loss of vision.

Always see a doctor or optometrist promptly if you develop visual loss or visual distortion.

Older people should in any case have regular eye checks to check each eye separately for early AMD (and to check for other eye conditions such as glaucoma).

How is age-related macular degeneration (AMD) diagnosed?

If you develop symptoms suggestive of AMD, your doctor or optician (optometrist) will refer you to an eye specialist (ophthalmologist). This should be done urgently, in case you have wet AMD (which can worsen rapidly but which can be treated).

The ophthalmologist may ask you to look at a special piece of paper with horizontal and vertical lines to check your visual fields. If you find that any section of the lines is missing or distorted then AMD is a possible cause of the visual problem. The ophthalmologist will examine the back of your eye with a slit-lamp microscope. Digital photographs can be taken of the retinae. The ophthalmologist will look for the typical changes that occur with dry AMD and wet AMD.

Another test called ocular coherence tomography is becoming more commonly used. This is a non-invasive test that uses special light rays to scan the retina. It can give very detailed information about the macula and can show if it is abnormal. This test is useful when there is doubt about whether AMD is the wet or dry form, and to monitor treatment.

If wet AMD is diagnosed or suspected then a further test called fluorescein angiography may be done. For this test a dye is injected into a vein in your arm. Then, by looking into your eyes with a magnifier the ophthalmologist can see where any dye leaks into the macula from the abnormal leaky blood vessels. This can give an indication of the severity of the condition.

What is the treatment for age-related macular degeneration (AMD)?

Whether or not there is a treatment that can prevent progression, or even reverse your condition, it is important to maximise the sight you do have.Stopping smoking and protecting the eyes from the sun’s rays by wearing sunglasses are important in slowing progression of the condition.A healthy balanced diet rich in antioxidants can be beneficial, as may the addition of dietary supplements (see below for details).

Does diet matter in age-related macular degeneration (AMD)?

Certain groups of people with AMD can benefit from vitamin and mineral supplements. These supplements can slow down the progression of AMD. They are thought to be most beneficial in people with intermediate or advanced AMD.

A combination of high-dose vitamins and minerals called AREDS2 has been tested and found to be most effective. These include:

  • 500 mg vitamin C
  • 500 mg vitamin C
  • 400 IU vitamin E
  • 10 mg lutein
  • 2 mg zeaxanthin
  • 25 mg zinc
  • 2 mg copper

High doses of vitamins and minerals can lead to side-effects in some people. Vitamin E has been linked with an increased risk of heart failure in people with diabetes or blood vessel (vascular) disease. Zinc may increase the risk of developing bladder and kidney problems. Because of these potential problems, you should talk to your GP or ophthalmologist before starting these supplements.

What else can I do?

  • If you smoke, try to stop. Smoking is a risk factor for many illnesses, including age-related macular degeneration (AMD). The NHS can provide help, support and medicines to assist stopping smoking.
  • If you smoke, try to stop. Smoking is a risk factor for many illnesses, including age-related macular degeneration (AMD). The NHS can provide help, support and medicines to assist stopping smoking.
  • Eat a healthy balanced diet to try to make sure you get plenty of the types of vitamins that may help in AMD.
  • Stay safe with regards to driving. If you are registered as having sight impairment you should not drive and should notify the Driver and Vehicle Licensing Agency.
  • Consider regular sight tests as you become older. An eye test can often pick up the first signs of an eye condition before you notice any change in your vision. Your optician (optometrist) can advise you how often you need to have an eye check-up, depending on your general health, age, family history and other medical conditions. Early detection of problems often allows more effective treatment.
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