Anti-vascular endothelial growth factor for macular edema secondary to central vein occlusion

Central retinal vein occlusion (CRVO) is thought to affect between one and four people per thousand at any one time, and is associated with increasing age, high blood pressure, diabetes, glaucoma and various disorders of the blood. It frequently causes sudden painless vision loss in one eye, although sometimes the vision loss may be minimal. If the vein blockage leads to inadequate oxygen delivery to the sensitive retinal tissue, the CRVO is considered to be of the 'non-perfused' or 'ischemic' subtype. More commonly, blood flow and oxygen delivery are restored following the vein blockage and the CRVO is considered to be of the 'perfused' or 'non-ischemic' subtype, which has a better visual outcome. Various other complications may develop over hours, days, weeks or months. These include macular edema (ME), in which fluid collects within the retina and causes reduction in vision. Until recently there has been no evidence-based treatment for this condition and many potential treatments, including laser, have been found to be ineffective. Recent studies suggest that an injection or implant of steroids in the eye may be of at least short-term benefit to patients with the perfused subtype of the condition. However, steroids are associated with significant side effects and there is currently no evidence that the benefit is sustained, or that patients with the non-perfused subtype of CRVO benefit from this treatment. Anti-vascular endothelial growth factor (anti-VEGF) agents have been used successfully to treat patients with other retinal vascular disorders, including several conditions associated with ME. Whilst anti-VEGF treatment appears to be associated with improved vision in a proportion of patients with perfused CRVO-ME, there are currently no well-designed studies with a sufficient follow-up time in the literature to allow a conclusion about their medium and long-term effectiveness and safety to be drawn. The outcomes of several trials with follow up exceeding one year are keenly awaited, and the use of anti-VEGF agents for CRVO-ME remains experimental.