Environmental factors have long been known to interact on an individual’s genes. The medical literature is replete with case studies of twins and siblings that share either all or half of their genome but often suffer very distinct medical conditions. One of the reasons behind such phenomena is a differential influence of diverse environmental factors – ranging from different micro-environments within the womb to diet, lifestyle and geography. Research within a population of glaucoma patients has revealed a correlation between the extent of visual field loss and a patient’s postcode. As remarkable as it may sound an analysis of the details shows that such a finding is not only predictable but also to be expected across the globe.