1905.] 



On the Production of Intraocular Fluid. 



299 



Great dilatation of the vessels of the ciliary processes and iris is produced. 

 The fluid, which, in the normal eye, is free from fibrinogen and contains the 

 merest trace of proteid, rapidly acquires the power of coagulation, and its 

 proteid content rises to 3, 4, or 5 per cent. The serious alteration of the 

 vascular structures is shown in many cases by the appearance of red blood 

 corpuscles in the fluid dropping from the cannula, and Greeff has shown that 

 if the lowered pressure be brought about suddenly and maintained for some 

 time, the epitbelium covering the ciliary processes may be raised from the 

 surrounding tissue so as to form small blisters, which are filled with coagul- 

 able lymph. It has been suggested by Greeff (4) that the change in composi- 

 tion of the intraocular fluid ensuing on opening the eye-ball is determined 

 by the separation of the epithelium, but Bauer (5) has shown that the proteid 

 contents may be raised in the absence of these epithelial changes, and that, 

 on the other hand, the epithelial changes may be well marked on the 

 subsequent day, when the wound in the cornea has closed, and the intra- 

 ocular fluid has regained its normal composition. He also points out that 

 the amount of change produced depends entirely on the rapidity with which 

 the intraocular pressure is lowered. The change in composition is probably 

 due, as Leber suggests, to the great distension of the capillaries and the 

 consequent separation of their endothelial cells. It represents in fact an 

 alteration in permeability of the filtering membrane. 



III. Amount of Intraocular Fluid Produced under Normal Circumstances. 



In any investigation of the factors determining the production and absorp- 

 tion of intraocular fluid, it is important to get some idea of the amount of 

 this fluid secreted under normal circumstances, that is at normal intraocular 

 pressure. Since the intraocular pressure is maintained constant so long as 

 the blood pressure is steady, the amount of fluid produced at a given intra- 

 ocular pressure must be equal to the amount of fluid absorbed at the same 

 pressure. It is therefore a matter of indifference whether we measure the 

 amount formed or the amount absorbed at any given pressure. Le Plat (6) 

 sought to abolish the absorption of the intraocular fluid by filling the 

 anterior chamber with oil or vaseline. A cannula was placed in the vitreous 

 cavity, and the pressure in the cannula maintained at the normal intraocular 

 pressure. It was found that the obstruction of the absorbing angle of the 

 eye-ball carried out in this way caused a rise of intraocular pressure if the 

 eye-ball were closed, or a flow outwards of intraocular fluid by the cannula 

 if the pressure in this was maintained at the normal intraocular pressure. 

 The amount of this outflow was measured, and was regarded by Le Plat as 

 representing the normal rate of formation of intraocular fluid. He arrived at 

 vol. lxxvii. — b. y 



