A comparison of four methods of cyclodeviation measurement was made (Cüppers Deviometer, Scale Maddox cylinder glass, Aulhorn Phase difference haploscope, Cüppers Synoptometer) with 25 complaint-free controls without cyclovertical deviations; the advantages and disadvantages of the instruments are described. Physiological peculiarities in the measurement of the subjective horizontals are demonstrated by the clinical example of a patient with decompensated paresis of the m. obliquus superior. The extent of cycloduction depends on the direction of rotation, from which the measurement is made, on the test object, and on the influence of normal environmental experiences ("Erfahrungsmotive" according to Bielschowsky). It is shown that a unilateral paresis of the m. obliquus superior can be compensated motorically by cycloversion. With "Erfahrungsmotiven" excycloduction can be found neither subjectively (subjective horizontal) nor motorically (regular position of the blind spot).