CENTRAL CONTROL OF EYE MOVEMENTS I 1 05 



R^NGE FINDER 



FUTURE POSITION DATA 



Typical fire-control insfallotion 



FIG. 12. A na\al stable platform for a fire control installation. The obser\'er using the range 

 finder and the director are on a platform which is stabilized against roll and change of 

 course (yaw). [From Gairdner (70).] 



which nearly led to accidents and forced the patient 

 to give up driving (95). In a description of his life 

 since he became deaf at the age of 15, a patient of 50 

 remarked on the movement of his field of view with 

 his head and added that "though this disability has 

 become modified with the passage of time, it is still 

 obvious when in a vehicle bumping over bad roads." 

 His illness was cerebrospinal meningitis apparently 

 with complete destruction of the vestibular apparatus 



(4). 



In view of this unequivocal histor\' extending over 

 35 years, one may perhaps cautiously differ from 

 Holmes who holds that \'estibular mechanisms are of 

 little importance in ocular disturbances since symp- 

 toms of this type are not permanent (83). If the 

 lesions are complete, their effects are in fact per- 

 manent. 



The existence of labyrinthine efTects on the eyes 

 in man is firmly established in the case of rotation 



about an anteroposterior axis, a movement which 

 cannot be carried out to order. The fact that the 

 movements of labyrinthine nystagmus may begin 

 with a latency of 50 msec, or thereabouts, whereas 

 those of optokinetic nystagmus have a latency of 

 over 200 msec, is further evidence for the existence 

 of labyrinthine reflexes in normal subjects. 



At this point the analogy from fire control in a 

 battleship is useful (see fig. 12). The platform which 

 carries telescopes for spotting naval or aerial targets 

 has to be stabilized against roll and change of course 

 and pitch, if that is a serious problem. "No one can 

 track with hand-operated telescopes specks in the 

 sky from a platform rolling erratically and unpre- 

 dictably" (70). Once the platform is stabilized, it is 

 easy to keep the target in the field of view of a tele- 

 scope and i)y fine adjustments of the telescope mount- 

 ing to keep the target upon cross wires. In the same 

 way, if the head and the eyes are stabilized against 



