766 PERCY FRIDENBERG 



Ocular Physiology 



But little is known of the endocrinological relations of the various 

 functions and physiological processes in the eye or of the influence upon 

 them of disorders of metabolism. Basic data are lacking in regard to 

 the details of physiological nutrition in the various ocular tissues, par- 

 ticularly the retina under varying conditions of light stimulation and 

 dark-adaptation. Similarly, the whole subject of intra-ocular tension as 

 a resultant of two processes, ciliary secretion and ocular filtration, must 

 be restudied from the standpoint of a science which will ask, for instance, 

 whether there are different rates, either of secretion or of elimination, un- 

 der varying conditions of body temperature, nutrition, endocrin balance, 

 stimulation of vagus or sympathetic, to say nothing of the question of 

 intra-ocular tension in Graves' disease, in obesity, in arteriosclerosis, or 

 its relation to other tensions, vascular, respiratory, iiitracranial or intra- 

 abdominal. 



Pupillary reactions have been studied very carefully and traced to 

 their cerebral, intracranial source. The various pupillcmctor paths 

 have been definitely mapped, but here again there is a lack of observa- 

 tions in health and disease of the special relation of pupillary reactions 

 to organ stimulation, to emotional states, and to endocrin influence. The 

 nerve control of the pupil by the vagus and sympathetic systems has 

 been noted under various headings of this survey, and an attempt has 

 been made to set up two types of ocular symtomatology, the vagotonic 

 and the sympathetico-tonic, guided largely by pupillary manifestations. 

 This division is suggested, as well, by a clinical determination of the in- 

 fluence of mechanical pressure on the eyeball, upon the rate of the heart 

 beat, the Oculo-Cardiac Reflex of Dagnini-Aschner. 



This reaction is elicited while the subject is at rest, after counting 

 the pulse or the heart beat for one minute, by continuous fairly firm 

 digital pressure on the closed eyes for the same length of time. The 

 pulse rate is then again determined. Normally there is a slowing of 

 three to five beats per minute, indicating the normal vagus tone. More 

 decided slowing, an increased reflex, indicates vagotoiiia. Absence of 

 slowing, absent reflex, or acceleration, inverted reflex, is indicative of 

 sympathetico-tonia. There is no consensus as to the significance of this 

 reaction, as yet. Numerous factors such as ocular tension, refraction, 

 age, and the coincident effect of mydriatics or meiotics must be taken into 

 consideration in health, while the observations in disease, systemic as 

 well as ocular, are by no means adequate or uniform. 



Winking and Tear Secretion. Both these physiological processes are 

 under a double vegetative nerve control which presents striking implica- 

 tions for function and pathology. There is in both cases a double func- 



