In previous studies * investigations were reported concerning the time characteristics of two of the most commonly executed types of eye movements, the so-called saccadic movements and the "smooth" movements elicited by moving visual stimuli. These are all conjugate movements, i. e., movements in which the two eyes move in parallel.
Disjunctive eye movements, i. e., movements in which changes take place in the orientation of one eye with respect to the other, are known to have time characteristics quite different from those of conjugate movements. Of particular interest in this connection are the movements of convergence and divergence during which the primary lines of sight of the two eyes remain in the same plane but change their relative orientation. They were first studied rather thoroughly by C. H. Judd.3 His method, however, did not enable him to obtain continuous records of eye positions. More recently they formed the subject
WESTHEIMER G, MITCHELL AM. Eye Movement Responses to Convergence Stimuli. AMA Arch Ophthalmol. 1956;55(6):848-856. doi:10.1001/archopht.1956.00930030852012