STUDIES ON THE INTRA-OCULAR FLUIDS: 1. The Reducing Substances in the Aqueous Humour and Vitreous Body

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Abstract
Cats and rabbits under nembutal anesthesia were employed. The glucose concn. in the aqueous is 15-20% less than that in the plasma. In the cat its concn. in the aqueous is 20% higher in the aphakic than in the normal eye. The glucose concn. in the aqueous in aphakia is less, however, than that in the plasma because the retina utilizes sugar. The glucose concn. in the vitreous of an excised eye is lower when the eye is incubated, and the decrease is most marked in the vitreous adjacent to the retina. The glucose concn. in newly formed aqueous, e.g., following paracentesis, or in the aqueous when the blood glucose concn. is artificially raised, is about 5% less than that of plasma. In both cases the metabolic factor is eliminated, and the 5% deficiency may be due to difficulty of entry of the molecule by the filtration process as compared with the freedom of its drainage with the aqueous. Glucose enters the aqueous more rapidly in the eserinized than in the atropin-ized eye. Eserine may diminish the block at the blood-aqueous barrier, but additional factors may be the increased iris surface, assuming that some aqueous is formed from iris, and the reduced lens surface presented to aqueous. The monosac-charides, pentoses and hexoses, enter the aqueous at compar-able rates and much more rapidly than the disaccharides. This may be an instance of cell membrane specialization. The glucose concn. in the vitreous is 50% less than that in the plasma and is evenly distributed. When the blood glucose is artificially raised, the anterior and posterior parts of the vitreous still have comparable glucose concns. This indicates that the areas of diffusion into the vitreous are not confined to the ciliary body. The retinal and choroidal capillaries contribute sugar after the retina has been supplied. The entry into the vitreous of pentose and xylose is 2 times, of hexose 3 times, and of sucrose 17 times as slow as that of the corresponding substances into the aqueous. The plasma-vitreous barrier appears more selective that the plasma-aqueous barrier.
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