[Illustration of the incomitance pattern in congenital unilateral obliquus superior paresis with the synoptometer...

The step-by-step measurement of VD (vertical deviation) by means of the synoptometer demonstrates the incomitance pattern clearly. This procedure was applied in 28 cases of congenital trochlear palsy. Three incomitance patterns of VD produced by the horizontal change of gaze were found: Adduction type: Absence of VD in abduction and primary position, marked increase in adduction. A zone of relative concomitance with comfortable binocular vision may be found. Linear type: Linear increase of VD with the movement toward adduction. Marked VD in primary position. Compensation more difficult. Mixed type: Linear type with marked VD in abduction. In all cases, the horizontal angle was very small, often together with a moderate V-incomitance. The incomitance caused by vertical change of gaze was only moderate. It occurred mainly between the horizontal and elevated positions. The above-mentioned classification and the classification based on incomitance with vertical change of gaze are compared.