Relative tensions in the extraocular muscles.

Two methods have been devised to assess the relative tensions required to point the eye in a given direction. One method uses an ophthalmotrope, which will assess the tensions and the lengths of the muscles. The second uses a computer program. In each method the direction of the eye is analyzed into components of elevation, azimuth, and cyclorotation. Such a combination of devices is needed in finding the patterns of innervation involved in Listing's law, cyclorotation associated with convergence, and also cocontraction associated with convergence.