Fig. 29—Position of rotary prism for producing diplopia in testing cyclophoria with prism placed at 8° base up.
Darken the room and direct the patient’s attention to the usual muscle-testing spot of light, located approximately twenty feet away and on a direct plane with the patient’s eye. The optical correction, if one is required, should always be left in place—just as in making other previously described muscle tests.
The rotary prism should then be brought before the patient’s right eye with the handle-pointing upward and with zero graduations horizontal. The indicator or red line should then be rotated upward from zero to eight upon the prism scale, creating the equivalent of a prism of 8 diopters with base up ([Fig. 29]). This normally caused diplopia, although in some cases it may be necessary to place the prism at 10 or 12 degrees before diplopia is produced.
Fig. 30—(A. and B.)—First position of both Maddox rods used in conjunction with [Fig. 29] for determining cyclophoria.
The red Maddox rod should then be brought into operative position before the patient’s left eye ([Fig. 30a]) and the white Maddox rod before the patient’s right eye, ([Fig. 30b]) setting each one so that the rods lie in a vertical position with their white line on the large red zero (0).
The patient should now see two separate and distinct streaks of light, one appearing below the other.
DETERMINING CYCLOPHORIA
Fig. 31