cross fixation

Cross fixation is the use of the left eye to view objects in the right field and the right eye to view objects in the left field, so that each eye fixates across the nose.^1,2 Cross fixation occurs in patients with infantile or accommodative esotropia and alternating fixation, and in patients with manifest-latent nystagmus.¹ Older literature also calls the behavior tripartite fixation.¹

In infantile esotropia the angle is usually larger than 30 prism diopters and stable, fixation alternates in primary position, and the child cross-fixates in side gaze.³ The majority of these patients cross-fixate, and amblyopia occurs in 25% to 40%.² The nonfixating eye makes no effort to abduct, so cross fixation can give a false impression of bilateral abduction deficits, as in bilateral sixth nerve palsy.^1,3 Covering one eye usually brings out full abduction in the uncovered eye, and the doll's head maneuver also demonstrates true abduction.^2,3

Cross fixation does not prove free alternation and does not rule out amblyopia.⁴ A child with equal acuity in both eyes switches fixation close to primary position as a target moves from one side to the other.^2,4 With amblyopia, the sound eye keeps following the target past primary position into abduction before the amblyopic eye takes up fixation.⁴