For patients with severe motor disabilities, a robust means of communication is a crucial factor for their well-being [1]. We report here that pupil size measured by a bedside camera can be used to communicate with patients with locked-in syndrome. With the same protocol we demonstrate command-following for a patient in a minimally conscious state, suggesting its potential as a diagnostic tool for patients whose state of consciousness is in question. Importantly, neither training nor individual adjustment of our system's decoding parameters were required for successful decoding of patients' responses.