Detection and measurement of the vertical phoria.

For the right eye (RE) and the left eye (LE) using the Maddox Rod Test in 14 subjects: vertical orthophoria (VO), hyperphoria (HR) and hypophoria (HP) which are vertical heterophoria (VH), respectively upward and downward deviation; and their prismatic correction: the amount (in diopter), orientation of the vertical prism - base up (BU) or base down (BD) - and the eye that received it (RE or LE) for the subject viewing was VO on both the left and the right.