Retinal Vein Occlusion

The retina is the inside lining of the back of the eye. It is composed of many layers of light sensitive nerve cells. Light entering the eye is focused on the retina and is converted to electrical impulses which are carried to the brain by the optic nerve. The centre of the retina is called the macula. It is the most sensitive part of the retina and is used for day light and colour vision. This is in contrast to the rest of the retina which is more sensitive in the dark and is mainly used for navigational black and white vision at night.

The retina is supplied by one main artery and one main vein which enter through the optic nerve and branch all over the retina to smaller arteries and veins that cross each other’s like railway tracks.

source – American Academy Ophthalmology

Occlusion of the retinal vein can occur by many causes. If the retinal artery wall becomes stiff (arteriosclerosis), it can compress a retinal vein at one of the crossing causing it to block and stopping its blood circulation. Another cause is increased tendency for blood to clot (hypercoagulability).

There are two types of retina vein occlusion, depending on the site of blockage. If the main central vein becomes blocked at its entrance through the optic nerve, it is called Central Retinal vein Occlusion (CRVO). Whereas if the blockage occurs at one of the branches, it is called Branch Retinal vein occlusion (BRVO).

When the retinal vein is blocked, its inside pressure increases leading to leakage of blood and fluid into the retinal tissue. The retina needs to be dry to work well and when it swells up, its nerve cells cannot conduct electrical stimulation well. This leads to impaired vision. Eventually some cells will die without good nourishment from blood circulation. This causes permanent loss of vision.

Central retinal vein occlusion (CRVO)

  • Blurred vision. This is the most common symptom and can occur suddenly or gradually over days. In some cases, blurred vision can be intermittent initially before becoming permanent. If branch retinal vein occlusion occurs outside the macular area, you may not notice any symptoms.
  • Floaters. These are dark spots or lines coming across the vision and are a manifestation of bleeding into the eye cavity (vitreous haemorrhage).
  • Pain. In advanced untreated cases, the eye pressure becomes elevated (glaucoma) leading to severe dull pain. Pain can also be caused in late stages if corneal ulcers developed.

Retinal Vein Occlusion almost always happens in one eye. In a small percentage of patients similar problems can occur later in the second eye.

  • Age: central retinal vein occlusion usually occurs in people older than 50. Whereas branch retinal vein occlusion can occur at any age.
  • High blood pressure (hypertension) is probably the most common association with retinal vein occlusion
  • Arteriosclerosis (hardening of blood vessels) and high cholesterol.
  • Overweight and obesity
  • Clotting problems; whether genetic or acquired
  • Diabetes
  • Glaucoma
  • Dilated retina examination: This is the standard test to check the back of your eye (retina). You will have your pupil dilated with drops so your vision will be blurry for an hour or two after the examination. Our specialist will check your eyes on the microscope (slit lamp) and use a special lens to see the details of the retina. The peripheral retina will be checked with another instrument called an indirect ophthalmoscope. You will also receive a full examination of the rest of both eyes including the front of the eye (anterior segment), your natural lens status and your eye pressure.
  • OCT (optical coherence tomography); this is a fast scan of the retina centre (macula) which shows cross section details of its layers. This test will identify any swelling caused by vessel leakage (macular oedema)

OCT of macular oedema

  • Fundus Fluorescein Angiography (FFA)

A fluorescent dye is injected into a vein in the arm or hand. The dye circulates rapidly in the body reaching the retina in a few seconds. A special camera will then take multiple quick pictures which show the dye in the retinal circulation clearly. This test helps us to detect swelling and leakage in the macula (macular oedema) and the degree of lack of blood supply to the retina (ischaemia). It also shows the early budding of new vessels in the peripheral retina (retina neovascularisation).

FFA of central retinal vein occlusion

  • Fundus Photography

This is a coloured photo of the retina that helps our specialists to have a record of your eye’s condition at that time and helps them in the long term follow up.

  • Ultrasound examination

If examination of the retina is not possible because of obstructing blood in the eye cavity (vitreous haemorrhage) then an ultrasound test is performed to assess the retina.

Ultrasound of vitreous haemorrhage

  • Blood tests

If you are younger than 50 years of age, you may need some blood tests to detect any abnormal clotting problems. For patients over 50, we will recommend that you visit your family doctor to do some blood tests to exclude diabetes and high cholesterol.

  • Observation: If vision is good at presentation, obsevation is recommneded as in some cases sponateous recovery will occur.
  • General medical checkup: We recommend that you visit your family doctor to check your blood pressure and to send you for blood tests to exclude diabetes and high cholestrol level. We may also send you for specific blood tests to check for rare clotting problems.
  • Anti-VEGF injections: This is now the main approach to treat swelling of the retina (macular oedema) caused by retinal vein occlusion. It involves injection of drugs into the eye cavity (vitreous). These drugs include Avastin, Lucentis and Eylea. They work by blocking the effect of chemicals produced in the eye with retinal vein occlusion called VEGF (vascular endothelial growth factor).This chemical is the cause of macular oedema and the development of new retinal vessels.
    Anti-VEGF injections are performed at the Norther Eye Centre without having to be admitted to hospital. They are done under local anaesthesia with no pain felt. You may need repeated injections every few weeks to prevent recurrence of macular oedema and maintain good vision.
  • Steroid injections: In some cases steroid drugs may be used to treat swelling of the macula (macular oedema). They can be in the form of a suspension or an implant that releases small doses of steroid over a few months. Repeated injections may also be necessary.
  • Laser treatment: Thermal laser has been used to treat the area of retina affected by the vein occlusion. It is applied to the patient whilst sitting in the examination room under anaesthetic eye drops.
    Laser may also be used as an added treatment for swelling of the macula (macular oedema) usually after a course of anti-VEGF injections.
  • Vitrectomy surgery: Surgery may be necessary for some patients who develop un-resolving vitreous haemorrhage (bleeding into the eye vitreous cavity) with retinal vein occlusion. The surgery is performed as a day case under local anaesthetic.

As in the rest of the body, to reduce the risk of blood vessel disease you need to maintain a healthy lifestyle.

  • Stop smoking
  • Maintain healthy body weight
  • Exercise regularly
  • Eat healthy food
  • Treat any high blood pressure and high cholesterol

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