The patient would instinctively describe, with pointed finger and hand motion, the position of the “dipping” line just as one would describe a spiral staircase. Should this test determine that no cyclophoria exists in either eye, there would be no necessity for further tests. Some authorities claim that both Maddox rods should be of the same color, so as to more readily assist the patient to fuse the two objects. If the reader so desires, he can readily place a red lens from the trial-case in the forward cell of the instrument. The characters _plus_ and _minus_ in cyclophoria merely refer to _plus_ as signifying a tendency toward the _temporal_ side; _minus_ indicating a tendency toward the _nasal_ side. This has no bearing on “convex” and “concave,” which are frequently designated as “plus” and “minus.” The test for cyclophoria is particularly essential, proving of utmost importance where the patient requires an astigmatic correction with the cylinder axis in oblique meridian. The case should then be investigated in every instance by making a thorough and separate test of each eye for cyclophoria. In a case where cyclophoria is determined, the trouble may be caused by the functioning of _other_ muscles, through the drain of nerve force, thus disturbing the harmony of _every_ muscle action. Cyclophoria is frequently caused by an imbalance of two recti, giving an oblique pull. In most cases, it is merely necessary to release the torsion, as described in the following chapter. CHAPTER XIV CYCLODUCTION TEST MADE WITH THE COMBINED USE OF THE TWO MADDOX RODS Having determined that cyclophoria exists, as previously outlined, the next step would be to make a cycloduction test, or a test of the oblique muscles individually. Maddox rods, both red and white, should be placed in position with the rods horizontal—the plus and minus sign at 90 degrees on the scale (Fig. 37). The patient’s attention should be directed to the usual muscle-testing spot of light, when a vertical band of light will appear to the patient, as shown in Fig. 38. [Illustration: Fig. 37—(A. and B.)—Primary position of combined use of both Maddox rods for determining cycloduction test.] [Illustration: _FIG. 38_ _NORMAL_] [Illustration: _FIG. 39_ _RIGHT +CYCLODUCTION_ _LEFT -CYCLODUCTION_] [Illustration: _FIG. 40_ _RIGHT -CYCLODUCTION_ _LEFT +CYCLODUCTION_ Figs. 38-40—Diagram showing position of streaks produced by Maddox rods as they appear to patients in making cycloduction tests.] To measure the duction range of the inferior oblique of the right eye, it is merely necessary to slowly rotate the Maddox rod before the right eye upward at its nasal end to the point where the band of light breaks so as to resemble a letter “X”. This gives in degrees the amount of right plus cycloduction, as indicated on the temporal scale, when it will appear to the patient, as shown in Fig. 39.