Objective and subjective evaluation of cyclovergence and cyclofusion.

There is a marked dispersion in the measured results of the angle formed by the intersection of the optic disc-center-meridian with the horizontal meridian, when the cycloposition of the eyes is determined through evaluation of the position of the optic disc (with fundus photographs or indirectly with perimetry). Values of the angle ranging from 0 degree at 12 degrees are still physiological. Inside this dispersion, individual right-left asymmetries of less than 4 degrees with photography and of less than 7 degrees with monocular perimetry are still normal as well. Positional differences of less than 4 degrees in sequential testings are also in a physiological range. The motor behaviour of both eyes during cyclofusion is evaluated by means of a perimetrical analysis of the blind spot at the phase-difference haploscope. Various sensory and motor adaptation phenomena are detected by comparing objective and subjective findings in patients with cyclotropia. These phenomena are discussed in detail.