VEGFA and edema: The reasons for inter-subject variation in response to anti-VEGF therapy in DMO are incompletely understood, with polymorphisms in the VEGF gene [12], differences in the VEGF gene expression [13], disease phenotype [14], glycaemic control [15], macular ischaemia [16], oedema chronicity [17, 18], subfoveal choroidal thickness [19] and foveal atrophy [17], variously implicated as possible contributory factors.