Nystagmus refers to bilateral involuntary rhythmic oscillation of the eyes, which can be jerky or pendular (jerk nystagmus and pendular nystagmus).
The various forms of nystagmus are listed in Table 17.5.
The etiology and pathogenesis of nystagmus remain unclear. Nys-tagmus is also a physiologic phenomenon that may be elicited by gazing at rapidly moving objects. An example of this is optokinetic nystagmus, a jerk nystagmus that occurs in situations such as gazing out of a moving train.
Where nystagmus can be reduced by convergence, prisms withan outward facing base may be prescribed. In special cases, such as when the patient assumes a compensatory head posture to control the nystagmus, Kestenbaum’s operation may be indicated. This procedure involves parallel shifts in the horizontal extraocular muscles so as to weaken the muscles that are contracted in the compensatory posture and strengthen those that are relaxed in this posture.