Glaucoma 425 



present time ophthalmologists are far from being agreed as to its 

 true pathology. All are agreed as to the essential feature of the 

 malady, namely, increased tension of the eye ball, but every case 

 of increased tension of the bulb is not recognized as glaucoma, 

 and the true cause of the persistent and progressive increase of 

 pressure in cases recognized as glaucoma is not absolutely settled. 



Causes. The immediate cause of the condition is the increased 

 intraocular pressure, on this all are agreed, but as to the cause 

 of this pressure there is difference of opinion. Grafe attributed 

 it to a serous choroiditis : Bonders to deranged innervation of 

 the 5th cranial nerve which controls secretion ; others to increased 

 blood pressure ; others to inflammatory contraction at the sclero- 

 corneal border where the principal drainage canal of the aqueous 

 humor lies. The increased blood pressure theory appears to be 

 contradicted by the fact that exalted blood pressure, as in fever, 

 does not tend to glaucoma. The arrest-of-drainage-of-the-aqueous 

 theory seems to be contradicted by the reduction of the anterior 

 chamber while the theory would demand its increase. Priestly- 

 Smith injected the sheep's eye with a pressure of water of 30 

 centimetres high, but while he caused an increased outflow he 

 failed to induce distinct glaucoma. MoUer tied the ophthalmic 

 vein of the horse, but he also failed to produce glaucoma. "By 

 artificial stimulation of the ciliary ganglion in dogs, the internal 

 tension of the eye can be noticeably and permanently increased, 

 and we may therefore assume that when this ganglion is stimulated, 

 the secretion of fluid is increased, and that glaucoma depends upon 

 an analogous process" (Fick). It would seem that necessity de- 

 mands at the same time an obstruction of the normal drainage 

 through nervous influence or otherwise. Schoen ascribes glaucoma 

 to overexercise of the accommodation, a cause which would hardly 

 be expected to operate in dogs. As bearing on the nervous cau- 

 sation Fick mentions that in man glaucoma is often preceded 

 and accompanied by trigeminal neuralgia. Again the symp- 

 toms of glaucoma often appear in the course of recurrent 

 ophthalmia in the horse. 



While it seems impossible to ascribe the disease to any single 

 definite cause there appears to be good reason to accept as 

 factors in different cases, a derangement of trigeminal innerva- 

 tion, an irritation of the ciliary ganglion, and an inflammation 



