The effect of lid elevation on the cross-cover test.

Abstract

To discern the effect of manual lid elevation on muscle balance using the cross-cover test. One hundred consecutive patients who were orthophoric in all fields of gaze were prospectively studied. A repeat cross-cover test was performed with the eyes looking down and to either side while pulling the lid ipsilateral to the abducting eye up and to either side. The presence and type of any phoria was noted. Eighty-four percent of patients and 76% of eyes developed a phoria with lifting a lid. Vertical phorias developed in 79 patients and 136 eyes, whereas horizontal phorias were seen in 51 patients and 83 eyes. In all but one case, the vertical deviation was a hyperphoria ipsilateral to the elevated lid. Horizontal deviations were esophoric in 63 eyes of 39 subjects. Induced phorias were most commonly symmetric from side to side. Lifting the lid produces an iatrogenic phoria that mimics a skew or IV nerve paresis. We hypothesize that stretching the lid causes traction on the levator-superior rectus complex, thereby increasing its tone. Although it makes testing more difficult, we recommend that the lids not be manipulated while performing phoria testing.