Exogenous Na-hyaluronate in the anterior chamber of the owl monkey and its effect on the intraocular pressure.

Exogenous, ultrapure (sterile, pyrogen-free), non-inflammatory fraction of Na-hyaluronate (NIF-NaHA) was introduced into the anterior chamber of owl monkeys (Aotus trivirgatus), replacing approximately 48% or 77% of the aqueous humor and creating post-injection intraocular pressures (IOPs) below normal (5-10 mmHg) or above normal (40-60 mmHg), respectively. Five different molecular weight samples (MW 1.7, 3.4, 3.7, 4.5 and 4.9 X 10(6)) were used. All solutions contained 1% NIF-NaHA and, because of the varying molecular weights, the viscosities of the solutions ranged between 10 000 and 930 000 cSt. The IOP and the rate of export of the exogenous NIF-NaHA from the anterior chamber were measured. All solutions caused an increase in the IOP, and the maximum level occurred at 4 hr after injection. In all cases, the IOP returned to normal 24 hr after injection. The highest and most persistent increase in IOP was observed after the injection of the solution with the lowest viscosity (10 000 cSt). The smallest increases in IOP over the post-operative value were observed after replacement of the aqueous humor using those samples with viscosities of 10 0000 to 300 000 cSt. The turnover (export rate) of injected NIF-NaHA depends for the most part on the viscosity of the injected solution. With increasing viscosity the rate constant, and therefore the half-life, of the injected NIF-NaHA decreases. The volume fraction of the viscous solution replacing the aqueous humor is also a determining factor in establishing the turnover rate. The molecular weight of the injected NIF-NaHA did not change during that time (48 hr) in which a sufficient amount of sample for analysis could be obtained. No evidence was found for the presence of any kind of hyaluronic acid-degrading agent in the anterior chamber.