1. A system for use in an assessment of an attentional deficit, comprising: a display; a camera configured to obtain a camera image indicative of a geometric relation between a head of a subject and the display during an assessment; and one or more processors configured by machine-readable instructions to: effectuate presentation of a test image on the display to the subject as part of the assessment; determine, based on the camera image, a deviation in the geometric relation between the head of the subject and the display from a reference geometric relation, wherein the reference geometric relation is determined based on a marker included in the test image; determine, based on the camera image, gaze points of the subject with respect to the display; and determine attentional deficit of the subject based on the determined deviation and the determined gaze points.