The term macular degeneration covers a spectrum of chronic and acute changes in the macular retina of both eyes and occurs in people aged 50 and above. One of the acute degenerative changes, choroidal neovascularisation, comprises an ingrowth of permeable and fragile new vessels from the choroid into the epithelial and subretinal spaces of the pigment layer,1 stimulated by pathological secretion of vascular endothelial growth factor (VEGF). In the United Kingdom choroidal neovascularisation causes severe visual impairment or blindness in around 3.5% of people aged 75 or more.2

Discovery of the role of vascular endothelial growth factor led to hypotheses that blocking or neutralising this factor might yield a treatment for choroidal neovascularisation.3 Clinicians had low expectations of success, however, because other new types of treatments had shown limited or no benefit. Moreover, the biological agents that induce blockade of the factor have many unwanted side effects. Given systemically, these drugs increase the risk of serious thromboembolic events. Given as intraocular injections they risk infection, haemorrhage, and undesirable ocular immune responses.

Despite these concerns, the absence of other effective treatments led to the vascular endothelial growth factor inhibition study in ocular neovascularisation (VISION), which provided proof of concept that intraocular inhibition of the growth factor for up to two years …