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.