Vertical vergence in convergence

PURPOSE: To report on a 7-year-old boy with a small left-over-right deviation (-VD) which increased when the head was tilted to the left shoulder and during convergence. METHODS: The squint angles were measured by the unilateral and alternate prism cover test at distance and near fixation when the head was in ortho-position and when it was tilted. RESULTS: At distance fixation (D) there was a latent deviation of-VD 3 degrees. With near fixation (N) at 0.3 m the vertical phoria increased to-VD 18 degrees. The angle of deviation was not influenced by (N) convex lenses in front of the fixating eye despite an adequate dis-accommodation. The-VD was fairly comittant in right and left gaze. At 45 degrees head tilt to the right shoulder the-VD decreased to (D) 2 degrees and (N) 12 degrees. At 45 degrees head tilt to the left shoulder the-VD increased to (D) 18 degrees and (N) 26 degrees. A dissociated vertical deviation was excluded by the dark red glass test and by the reversed fixation test. CONCLUSION: The disturbance can be explained by a, presumably congenital, supranuclear misinnervation and has to be differentiated from other types of vertical deviation.