What to do... if you have a retinal vein occlusion

A pdf copy of this leaflet can be found here.

Retinal vein occlusion (RVO) refers to the blockage of one of the retinal veins. Either a branch retinal vein can be blocked (branch retinal vein occlusion, BRVO) or the central retinal vein can be blocked (central retinal vein occlusion, CRVO). As the retina has no overlapping blood supply, i.e. any part of the retina is only supplied by one arteriole and one venule, blockage of a retinal vein will result in back pressure building up in the area of the retina affected, leading to bleeding and swelling.

Most patients with a retinal vein occlusion will notice a change in their vision. The central vision can be blurry or distorted due to swelling at the macula (cystoid macular oedema). There will also be bleeding in the retina, which some patients will notice as black spots. The severity of the vision loss is dependent on the type and location of the vein occlusion, (i.e. BRVO or CRVO, and if BRVO, if a major branch is blocked or if the blockage involves the macula), and how severe the blockage is. A mild blockage will result in minor haemorrhage and minimal symptoms, where a severe blockage can lead to minimal blood flow in the retina and secondary inner retina ischaemia.

If you have been diagnosed with a retinal vein occlusion, you need to consider the following to ensure your eyes are well treated.

Find out the type and severity of the vein occlusion

First of all, you need to find out if you have a branch retinal vein occlusion or a central retinal vein occlusion, and if it is macular involving. There should also be an estimation of severity of the vein occlusion.

• Mild RVO - The involved retinal vein will be tortuous, and there will be only a few haemorrhages. There should not be any cystoid macular oedema on OCT, and the acuity should only be minimally affected (generally 6/9 or better). The patient is either asymptomatic or minimally symptomatic of the condition.
• Moderate RVO - There are mild than a few haemorrhages and there will be cystoid macular oedema affecting vision. Visual acuity will be less than 6/9 and the patient is symptomatic, but there should not be any signs of inner retinal ischaemia.
• Severe RVO - There will be severe haemorrhages and evidence of inner retinal ischaemia (significant increased signal in the inner retinal layers, loss of lamination in inner retina and cotton wool spots). There can be severe cystoid macular oedema, but in very severe occlusion with ischaemia, cystoid macular oedema can be absent due to a lack of blood flow. Visual acuity is invariable severely affected (6/60 or less), and the patient significantly symptomatic.
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Assess and optimise systemic and ocular risk factors

Systemic risk factors

Age is the major risk factor for RVO. Cardiovascular risk factors are associated with RVO, and these include hypertension, hyperlipidemia, diabetes, and coronary artery disease. As BRVO is more likely associated with arterio-venous crossing changes, these cardiovascular risk factors are more important in BRVO.

Haematological factors (e.g. factor V Leiden and homocysteinaemia, anti-phospholipid syndrome or conditions that increase blood viscosity) play a more important role in CRVO than in BRVO. Carotid occlusive disease and sleep apnoea have also been implicated in CRVO. In patients younger than 50 years old with CRVO, 58\% has a non-traditional systemic risk factor.

COVID infection has been identified as a risk factor for RVO.

Ocular risk factors

Previous RVO is a risk factor for RVO in the fellow eye. The risk of CRVO in the fellow eye is 1\% per year for a patient with previous CRVO, and for a patient with BRVO, the risk of any RVO in the fellow eye is 10\% over 3 years.

Retinal vasculitis has been identified as a risk factor for BRVO. In CRVO, raised intraocular pressure and glaucoma are risk factors.

Recommendations for risk factor assessment

All patients with CRVO should have their intraocular pressure measured and their drainage angles assessed for risk of intraocular pressure spikes. One should also exclude intraocular inflammation by looking for cells in the vitreous.

For patients over the age of 50 with well documented cardiovascular risk factors, usually no additional assessment is required, although a carotid duplex ultrasound can be considered to rule out carotid artery stenosis. For those over the age of 50 with CRVO and no known cardiovascular risk factors, a referral to a haematologist is required to rule out haematological factors. One should also enquire sleep apnoea in these cases. In the elderly, one should also consider rare conditions that increase viscosity, such as multiple myeloma, in the absence of any other risk factors.

For patients younger than the age of 50 with no cardiovascular risk factors, detailed assessment is required with particular care to exclude both haematological factors and inflammatory conditions (such as anti-phospholipid syndrome) associated with RVO.

Optimisation of modifiable risk factors are important to lower the risk of future RVOs, but this does not change the treatment and prognosis of the existing RVO.

Treatment with anti-VEGF for RVO

Patients with moderate or severe RVO should have anti-VEGF treatment. These injections will decrease the vascular leakage of the retina, decrease cystoid macular oedema, and improve visual acuity. Furthermore, peripheral haemorrhages tend to improve with anti-VEGF treatment and often the vascular tortuosity improves. This suggests anti-VEGF injections has more beneficial effects over simply reducing vascular permeability in RVO.

Anti-VEGF agents available in New Zealand include bevacizumab (Avastin), ranibizumab (Lucentis), aflibercept (Eylea), and ziv-aflibercept (Zaltrap). These are given as injections into the eye once a month to start with, and the treatment interval adjusted according to response. You can find more information about intravitreal injections in a separate leaflet on leosheck.co.nz.

In patients with severe CRVO with inner retinal ischaemia without cystoid macular oedema, a case series suggests that anti-VEGF injections still have beneficial effect, and a trial of treatment should be considered.

In patients with mild RVO without cystoid macular oedema, anti-VEGF injections should be considered if they are symptomatic with vision changes. In these cases, a fluorescein angiogram will demonstrate vascular leakage despite the absence of cystoid macular oedema, and anti-VEGF injections will control and reduce the peripheral leakage.

Ideally anti-VEGF therapy should be started within a week of diagnosis, but there is still beneficial effect even if the treatment is deferred by up to 6 months. Long standing cystoid macular oedema from RVO tends to be difficult to treat and does not respond fully to treatment.

Prevent neovascular complications

In severe RVO, there is a lack of blood supply to the peripheral retina, and this can trigger the growth of abnormal blood vessels. In BRVO, often these new blood vessels are seen in the peripheral retina and they can cause bleeding into the vitreous cavity of the eye. This will lead to a sudden formation of floaters and vision loss. In CRVO, abnormal blood vessels can form in the iris and the drainage angle, and this can cause severe elevation of the intraocular pressure, pain, and vision loss.

These abnormal new blood vessels will not form if a patient is on regular anti-VEGF injections, but can start to grow when the injection treatment is tapered off. For most patients with RVO, a fluorescein angiogram using Optos ultra widefield camera should be considered when the peripheral haemorrhages have improved to assess retinal perfusion. Panretinal photocoagulation treatment can be considered if there is significant non-perfusion (see leaflet on Retinal Laser on leosheck.co.nz).

Patients with CRVO are at risk of ischaemic transformation, and the risk is the highest within the first 90 days of diagnosis.

Consider intravitreal steroid therapy for recalcitrant oedema

Not all patients respond to intravitreal anti-VEGF therapy. In those patients with ongoing cystoid macular oedema despite anti-VEGF, intravitreal steroid (triamcinolone / ozurdex) treatment can be considered. However, this carries a risk of raised intraocular pressure, cataract formation, and in the case of triamcinolone, inflammation inside the eye.

Dr Sheck can discuss if this is appropriate for you in your appointment.

Experimental therapy

Formation of a chorioretinal anastomosis has been studied by a group in Perth for the treatment of RVO. Furthermore, suprachoroidal placement of steroid has been tried for the control of cystoid macular oedema in RVO. Neither modality has found widespread acceptance, and are not used clinically at this stage.

Long term prognosis

Most people with retinal vein occlusion will have formation of collateral vessels (bypass vessels) over time, and this can reduce the pressure within the venous system. Sometimes this is sufficient for the condition to settle and the injection therapy discontinued. In some other cases, the injection therapy will need to be continued long term to help preserve central vision.

It is not possible at the onset of the disease to predict how many injections one would require for the treatment of the disease. However, it is clear that for most patients with retinal vein occlusion with the cystoid macular oedema adequately controlled, the long term visual prognosis is good.

About Dr Leo Sheck

Dr Sheck is a RANZCO-qualified, internationally trained ophthalmologist. He combined his initial training in New Zealand with a two-year advanced fellowship in Moorfield Eye Hospital, London. He also holds a Doctorate in Ocular Genetics from the University of Auckland and a Master of Business Administration from the University of Cambridge. He specialises in medical retina diseases (injection therapy), cataract surgery, ocular genetics, uveitis and electrodiagnostics.