A device (10) is used to determine the presence of and the amount (depth) of visual suppression in a subject. The device includes a first light source (20L) emitting a first light and a second light source (20R) emitting a second light. Intensities of the light sources are independently controllable. A first filter (32L) disposed over one eye of the subject allows transmission of the first light and prevents transmission of the second light. A second filter (32R) disposed over the other eye of the subject allows transmission of the second light and prevents transmission of the first light. In a method of using the device, the intensity of at least one of the first and second lights is independently controlled, wherein the difference in intensities of the first and second lights at which the lights appear to be at equal brightness to the subject determines the amount of visual suppression in the subject.
