Intravitreal Bevacizumab for Primary Treatment of Diabetic Macular Oedema

Abstract and Introduction

Abstract

Background: To evaluate the effectiveness of intravitreal bevacizumab injection as primary treatment of diabetic macular oedema.
Material and Methods: Thirty eyes of 30 diabetic patients were treated with 2.5 mg of intravitreal bevacizumab injection as the primary therapy for diabetic macular oedema. The main outcome measures included best-corrected visual acuity, fundus fluorescein angiography, and macular oedema map values of Heidelberg retinal tomograph II (HRT II) before and after intravitreal injection.
Results: The visual acuity increased in 24 of 30 eyes (80%) during a mean follow-up time of 5.6 months. The mean baseline best-corrected LogMAR value for visual acuities of the patients before intravitreal bevacizumab injection was 1.09±0.23. After treatment, it was 0.90±0.17 at the 1-month, 0.81±0.24, at 3-month, and 0.77±0.26 at the last visit examinations and the differences were significant when compared with baseline values (for each, P<0.001). The mean oedema map values significantly decreased by 33.3% at the last visit examination when compared with preinjection values (P<0.001). Mild anterior chamber inflammation was observed in four eyes (13.3%), which resolved in a week with topical corticosteroid. No other injection- or drug-related complications were observed.
Conclusion: Intravitreal bevacizumab application provides significant improvement in visual acuity of diabetic patients and clinical course of macular oedema, and may therefore be a promising approach in the primary treatment of diabetic macular oedema.

Introduction

Macular oedema is the most common cause of visual impairment in diabetic patients. The exact pathogenesis of diabetic macular oedema (DME) has not been elucidated, although a breakdown of the inner blood-retinal barrier seems to be a reasonable explanation. The important pathophysiology of DME is the loss of retinal capillary pericytes, resulting in increased vascular permeability.^{[1,2,3,4,5,6]} The 3-year risk of moderate visual loss due to macular oedema was 32% in the Early Treatment Diabetic Retinopathy Study (ETDRS). Focal macular laser photocoagulation has been shown to be effective in the treatment of DME in a large prospective multicenter randomized clinical trial of ETDRS.^[7] However, some treated eyes may be resistant to laser photocoagulation or efficient laser treatment could not be performed due to diffuse macular oedema. Therefore, the failure of laser photocoagulation in these eyes has prompted interest in other treatment modalities, such as intravitreal triamcinolone acetonide (IVTA) injection,^[4,5,8,9] pars plana vitrectomy,^[10,11] or treatment with protein kinase C inhibitors.^[12]

Retinal hypoxia is the primary cause of diabetic retinopathy, which increases expression of vascular endothelial growth factor (VEGF). As known, VEGF is a potent inducer of vascular permeability that has been shown to cause leakage from retinal vessels and contribute to DME.^[13] Bevacizumab (Avastin, Genentech Inc., South San Francisco, CA, USA), a full length, humanized monoclonal antibody against VEGF, also binds and inhibits all the biologically active forms of VEGF, and approved by the Food and Drug Administration for the treatment of metastatic colorectal cancer.^[14,15] Bevacizumab has been used for intravitreal injection in patients with choroidal neovascularization, iris neovascularization, vitreous haemorrhage, and macular oedema, and shown to provide beneficial effects in such patients.^{[16,17,18,19,20]} However, there is only one study showing the beneficial effect of intravitreal bevacizumab therapy for persistent diffuse DME.^[20] Therefore, this study investigated the efficacy of intravitreal bevacizumab for primary treatment of DME by using Heidelberg retinal tomograph II (HRT II).