Devices, systems and methods for predicting gaze-related parameters

A head-wearable spectacles device for determining one or more gaze-related parameters of a user is disclosed. In one example, the device includes a spectacles body having a middle plane and configured for being wearable on a user's head, and at least a left and a right ocular opening, wherein both ocular openings define a bounding cuboid having an upper surface, a lower surface, a left lateral surface, and a right lateral surface. The upper surface of the bounding cuboid is oriented perpendicular to the middle plane of the spectacles body.