Figure 2.

The various radiographic measures of horizontal gaze. (A) Chin brow vertical angle; (B) slope of line of sight—angle between a line drawn from inferior margin of the orbit to the superior border of the external auditory meatus and the horizontal; (C) McGregor’s slope—angle between a line drawn from the posterosuperior corner of hard palate to opisthion and the horizontal; (D) the ‘3-6-12’ rule: a = vertical distance from horizontal line drawn from middle of orbit to base of sella turcica. b = angle between line drawn from middle of orbit to internal occipital protuberance and horizontal.