eye gaze systems

has anyone had any experience with an “eye-gaze” system? i am trying to gather information to help my dad with his communication. i have found one that accepts medicare but i am not sure, with the potential prognosis of recovery, if they will pay for it. does anyone know if GBS is considered a “locked-in” syndrome. i mean, i know that technically, it is. but do you know if insurance/medicare may consider it so?