The previous article about retinal vein occlusion (RVO) discussed the types and causes of retinal vein occlusion. Patients who suffer from RVO may have very severe loss of vision and often have other significant health problems like high blood pressure, diabetes, and high levels of cholesterol in the blood. In this article, we will discuss the ways of preventing RVO from occurring and the latest treatments of RVO.

Prevention of retinal vein occlusion

Patients with high blood pressure, high levels of cholesterol in their blood, and who have diabetes are at increased risk of developing RVO. It is important to ensure that these common diseases are well controlled in order to reduce their future risk of getting RVO. Patients with rare diseases like thrombophilia (blood clotting disease) or high levels of homocysteine are also at risk of RVO and need good control to prevent it from occurring.

Once a patient has got RVO in one eye, they have a 15% chance over 5 years of getting it again in the same eye or the other eye. It is important to screen these patients for those diseases in order to treat them to prevent future occurrences of RVO. Patients with RVO have a higher risk of death from heart attacks and stroke and it is even more important to treat these systemic diseases, especially high blood pressure, well to prevent that from happening.

Treatment of retinal vein occlusion

Treatment of RVO can be divided into two main categories:

1. To improve vision by treating macula oedema
2. To prevent complications like glaucoma (raised eye pressure) and bleeding in the eye

The two main ways of treating RVO is by using laser to create burns on the retina and by injecting drugs into the eye.

Treatment of macula oedema in retinal vein occlusion

Macula oedema (fluid in the inner layer of the retina) is the main cause of visual loss in RVO. The macula is the most important part of the retina as it detects fine detail and colour. In the past, laser treatment was done on the areas of the retina that was swollen with fluid. For patients with central retinal vein occlusion (CRVO), this was not found to be effective. For patients with branch retinal vein occlusion (BRVO), laser treatment has some small benefit.

Recently, new scientific data has shown that several drugs may be better than laser treatment for macula oedema in RVO. These drugs need to be injected into the eye and include triamcinolone, Ozurdex (a long term steroid implant), and Lucentis (an antibody to vascular endothelial growth factor (VEGF)). The main risk of any eye injection is an infection but fortunately, this is rare and occurs in 1 out of 2000 injections. If an infection occurs, it can be easily treated with antibiotics. Very rarely, loss of vision can occur if the infection is very severe.

1. Intravitreal injection of Triamcinolone Acetonide (IVTA)        

Triamcinolone acetonide is a steroid drug that is often used from injections into bone joints with arthritis. A large study from the USA (SCORE study) has reported that IVTA is effective for treatment of macula oedema in patients with CRVO after 1 year of follow-up. It was not better than laser therapy for macula oedema in patients with BRVO. Some patients needed a repeat injection after 4 months.  The main problem with this treatment is that more than 30% of the patients treated will get cataract and glaucoma (raised eye pressure) that requires further treatment. IVTA has been widely used worldwide for the last 8 years for other retinal diseases like diabetic macuolopathy macular degeneration.

2. Intravitreal injection of a long term steroid implant (Ozurdex)            

Ozurdex is a special implant that contains dexamethasone (a steroid drug). Once injected into the eye, it gradually releases the drug over a 6 months. It has recently been approved for use in the USA but is not yet available in Malaysia. The results show that patients with macula oedema due to CRVO or BRVO both had improvement of vision after this treatment. In terms of side effects, 25 % of patients developed glaucoma while less patients compared with IVTA treatment (4% ) developed cataracts.

3. Intravitreal injection of Lucentis            

In RVO, there is an increase in the levels of a particular growth factor called vascular endothelial growth factor (VEGF). VEGF causes macula oedema to occur and special new antibody drugs to block this molecule have been developed. Lucentis is a VEGF antibody that was developed specifically for injection into the eye for another common eye disease, age-related macula degeneration.

Recently, two large studies in the USA (The CRUISE and BRAVO trials) have reported the effectiveness of Lucentis in treating macular oedema in CRVO and BRVO comparing it with laser therapy. Treatment was given every month for 6 months. Patients were found to have rapid improvement of vision 1 week after the 1st injection which was maintained for 6 months. The visual improvement found in the Lucentis treated group was much better than the laser therapy group and patients who received Lucentis injection were twice as likely to get a significant improvement compared to those receiving laser therapy. Very few side effects were found to occur in the Lucentis treated patients.

Figure 1: An optical coherence tomography (OCT) scan of a patient’s macula. This is a special cross sectional image of the retina created by a special laser beam. There is macula oedema present due to CRVO. The layers of the retina are normally close together without any fluid inside. The black spaces seen in the layers of the retina seen here is due to swelling caused by the fluid. The patient’s vision is significantly reduced by the macula oedema

Figure 2: OCT scan of the same patient’s macula 1 month after treatment with intravitreal Lucentis. The retina layers have returned to normal as the oedema has resolved. The patients vision has improved after treatment.

Treatment to prevent complications in retinal vein occlusion

The two main complications of RVO are glaucoma and bleeding in the eye. This occurs due to abnormal new blood vessels growing inside the eye due to the lack of oxygen caused by the RVO. These blood vessels can bleed easily inside the eye and cause loss of vision. The eye pressure can also increase and cause the eye to become completely blind and painful. To prevent this from happening, it is sometimes necessary to perform laser treatment on the retina. These laser burns destroy the peripheral parts of the retina to prevent these new blood vessels from growing. It can also cause these new blood vessels to disappear. Patients with RVO have to be seen in the eye clinic regularly to detect these new blood vessels for treatment to be given promptly to prevent these complications from occurring.

Conclusion

Retinal vein occlusion is a serious eye disease that can cause significant loss of vision. It is often associated with other diseases like high blood pressure. New treatments are available that can help improve vision. These treatments involve injection of drugs into the eye. While steroid injections in the eye do work, there is a high percentage of patients who will develop complications like cataract and glaucoma. Intravitreal Lucentis injections have to be given every month for up to 6 months but it appears to be very effective at improving vision and has very little side effects compared to the steroid injections.