Abstract
The concentrations of six major intraocular fluid (IOF) constituents were compared in phakic and aphakic rabbit eyes in order to study the role of the lens in the maintenance of normal concentration gradients between the aqueous and vitreous and to help reveal other sites of solute utilization and transport in the mammalian eye. The protein concentration was transiently increased after extracapsular lens extraction in both the aqueous and the vitreous, while that of ascorbic acid was decreased in the aqueous. A new steady state of these substances was achieved by 10 weeks, at which time the concentrations of ascorbic and lactic acids were lower while glucose was significantly higher in the aqueous of the aphakic as compared to the contralateral phakic eye. In the vitreous the concentration of K + was decreased and that of total amino acid was increased. Upon incubation of aphakic eyes in vitro, the concentration of K + increased and glucose decreased in both aqueous and vitreous at a rate similar to that of incubated phakic eyes. Paracentesis, surgical trauma, and inflammation may account for the initial effects of lens extraction. Some of the long term changes can be accounted for by the elimination of an organ that normally utilizes substances from, and releases metabolites into, the aqueous and the vitreous and acts as a partial permeability barrier and a transport site between these compartments. The present study indicates, however, that the lens makes lesser metabolic demands on the vitreous than the retina. It also supports the concepts that there is a net K + flux across the lens and an active removal of K + from the extracellular fluids of the retina and, hence, from the vitreous across the blood-retinal barrier. Rapid release of K + into the vitreous of isolated aphakic eyes suggests that the retina responds to asphyxia or ischemia with release of intracellular K + before its metabolic resources are exhausted.
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