Intravitreal Bevacizumab (Avastin®) Versus Intravitreal Dexamethasone (Ozurdex™) for Persistent Diabetic Macular Oedema

Overview

The specific aims of the study are to test the following hypotheses: * That there is a difference in change in visual acuity resulting from treatment with intravitreal bevacizumab compared with dexamethasone implant in eyes with advanced macular oedema * That there is a difference in degree of resolution of macular oedema resulting from treatment with intravitreal bevacizumab compared with dexamethasone implant in eyes with advanced macular oedema * That both intravitreal bevacizumab and dexamethasone implants have a manageable and acceptable safety profile in eyes with diabetic macular oedema

Diabetic retinopathy is a common cause of severe loss of vision and the most common cause of blindness in individuals between the ages of 20 and 65 years in developed countries. Swelling of the central retina, or "macular oedema", is the commonest cause of visual loss in diabetic retinopathy. Diabetic macular oedema (DMO) is treated with laser photocoagulation of areas of leak in the macula according to established guidelines which take into account the extent of the leak and its proximity to the centre of the macula, the "fovea". This treatment does not always work, however, and is inherently destructive. New drugs have become available which appear to reduce the risk of loss of vision in eyes with advanced diabetic macular oedema for which further laser treatment is unlikely to be beneficial. Intravitreal injection of slow-release steroid formulations such as Ozurdex™, a slow release formulation of dexamethasone, has been proposed as a new modality to treat clinically significant DMO. We have recently conducted randomised clinical trials which have demonstrated that treatment with intravitreal triamcinolone (IVTA) leads to reduction of DMO and improved vision in these eyes. Another class of drugs, inhibitors of Vascular Endothelial Growth Factor (VEGF) such as bevacizumab (Avastin®), also appear efficacious. While both drugs appear to reduce macular oedema and improve vision in the short term, they may have differences which could guide how they are best used. Around 1/3 of eyes that receive dexamethasone may develop elevated intraocular pressure and cataract, both of which are manageable but may complicate the picture. Anti-VEGF drugs do not have these local adverse events, however they must be given more frequently (4-6 weekly vs 4-6 monthly for Ozurdex™) and it is suspected they may have a neurotoxic effect on the retina. Some authorities suspect that anti-VEGF treatment may be associated with a small increased risk of having a stroke or heart attack during treatment, even when they are injected into the eye. This has not been proven with a related drug, ranibizumab, but it is still possible that it may occur with bevacizumab. This will be a, 2 year, phase II, prospective, multicentre, randomised, single-masked clinical trial of sustained release intravitreal dexamethasone (Ozurdex™) versus intravitreal injections of bevacizumab (Avastin®) for diabetic foveal oedema that persists or recurs despite previous laser treatment, or for which the investigator believes laser treatment is unlikely to be helpful.