[Reflections on expert assessment of double vision and forced head position]

Visual impairment in patients with diplopia can be assessed using a scoring method in front of a tangent screen. The primary position is the starting position for these measurements. For medicolegal judgement the scoring is based on a suggestion of Haase and Steinhorst, ranging from a disability of 0% to 25%. A new proposal for scoring the field of binocular single vision (BSV) is made here: A field between 30 degrees right and left gaze, 20 degrees upgaze and 40 degrees downgaze is defined as used under every day conditions. It is divided such that diplopia in one lateral half field corresponds to 13% disability, in the upper half 10% and in the lower 18%. Patients suffering from a unilateral superior oblique palsy often show a slight torticollis. In these cases the habitually assumed head position should be taken as the starting posture for the tangent screen measurements.