Aim: The spread of epileptic activity within the cortex is opposed by a powerful inhibitory restraint. We hypothesized that the same inhibitory mechanisms are likely also to underlie the phenomenon of surround suppression, as occurs during normal visual processing. This raises the possibility that visual psychophysical assessment of surround suppression could offer a non-invasive way of measuring network state in epilepsy. Methods: We recruited 146 healthy volunteer controls and 54 patients with clinically confirmed epilepsy. Two different stimulus paradigms (motion direction discrimination (Tadin et al, 2003) and contrast detection task (Serrano-Pedraza et al, 2012)) were used to derive surround suppression indices. These were designed to work on a tablet computer, which the patients could use either in clinic or in their own home. Results: Surround suppression indices derived from the motion discrimination task, but not the contrast detection task, were significantly higher in patients with frequent seizures compared to patients with infrequent seizures or controls. In a longitudinal study, patients showed higher between subject and within-subject variations compared to controls. Furthermore, the motion suppression index of patients with exclusively focal epilepsy was significantly higher than in patients with focal epilepsy evolving into bilateral convulsive seizures, GGE or controls. Conclusions: Visual psychophysics provides a simple and non-invasive means of assessing the state of inhibitory networks involved in the pathophysiology of epilepsy. The inability to increase activity in inhibitory networks in response to focal epileptic activity may predict the risk of generalised seizures, which may in turn allow stratification of SUDEP risk.