THE FORMATION OF THE INTRA-OCULAR FLUIDS. STUDIES OF THE UREA COMPONENT OF THE AQUEOUS HUMOUR

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Abstract
The rate of penetration of urea into the aqueous is higher than that in the vit reous, the permeability constant for the former (KA) being 11.9 and that for the latter (KV) 5.4. There is a 20% deficit of urea in the intra-ocular fluids as compared with plasma, and in vitro and in vivo expts. show that this deficit is not due to utilization of urea by the lens or other ocular tissues. Urea does not traverse the blood-aqueous barrier by a simple ultra-filtration because unilateral carotid artery ligation, which causes a fall in B. P. in the homolateral eye and therefore an upset in any ultra-filtration mechanism, is without influence on the urea concn. in the aqueous. Some mechanism appears to exist at the barrier which regulates the entry of fluid into the eye without reference to the systemic B. P.