X pattern

An X pattern is a horizontal strabismus with exotropia in upgaze and downgaze and little or no deviation in primary position. The X pattern is one modification of the classic A and V patterns, along with the Y and inverted Y (lambda) patterns.¹ All of these alphabet patterns turn up in intermittent exotropia.²

An X pattern may come with overaction of both the superior and inferior oblique muscles. In some of these patients the oblique dysfunction disappeared once the horizontal strabismus was corrected, which suggests that the oblique dysfunction can be secondary to the exotropia.¹ Contracture of the lateral recti in long-standing intermittent exotropia can also make the adducted eye overelevate or overdepress and mimic oblique overaction. Forced duction testing of the oblique muscles separates true overaction from merely tight lateral recti.²

An X pattern can also occur in Duane retraction syndrome, along with upshoot or downshoot of the adducting eye.³