The Maddox rod or suppressed-image or obscuration test in some of its forms, and the prism or diplopia test in some form of phorometer, are most commonly used in the determination of the co-ordination of the external muscles of the eyes. In this practice it is assumed that there is a functional position of rest for the eyes in binocular vision, and that in this position of rest, the lines of vision are both directed toward the point of fixation. It is not my purpose to discuss here the nature or limits of this co-ordination, the causes which disturb it, or the effects, or treatment of any disturbance of it. My only question is as to the comparative value of the diplopia test, by Stevens' phorometer.
Using Stevens' nomenclature, I assume that orthophoria is the strictly normal condition of ocular co-or dination, although I grant that there may be, within
HUBBELL AA. THE MADDOX ROD OR PHOROMETER: WHICH?. JAMA. 1900;XXXIV(7):403-405. doi:10.1001/jama.1900.24610070019001j