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In their article, entitled "Efficacy of Hyaluronidase in Reducing Increases in Intraocular Pressure Related to the Use of Viscoelastic Substances," Harooni et al1 show that elevation of intraocular pressure after injection of hyaluronic acid (HA) containing viscoelastics was prevented by coinjection with hyaluronidase. The authors claim that the pressure-lowering effects of hyaluronidase in the presence of intracameral HA are related to the degradation of injected sodium HA (NaHA) rather than native trabecular NaHA molecules. Our previously published results support this hypothesis.2,3 In a rabbit model, we measured intraocular pressure for 12 hours after intracameral injection of HA (Healon; Pharmacia, Uppsala, Sweden), 10 mg/mL, and solutions of HA that had been degraded by hyaluronidase (Wydase; Wyeth-Ayerst, Philadelphia, Pa) for varying periods (5 minutes, 15 minutes, or 24 hours). Prior to injection, sepharose CL-4B (Pharmacia, Uppsala, Sweden) gel filtration of the enzymatically degraded HA solutions demonstrated that the elution profile shifted progressively to the right (ie, smaller molecular weights) as a function of degradation time by hyaluronidase. We found that intraocular pressure elevation in these rabbits was inversely proportional to the duration of hyaluronidase degradation of the injected HA. For HA solutions degraded for 15 minutes or more, intraocular pressure was not statistically different than in untreated controls. These findings suggest that intraocular pressure elevation after intracameral injection of HA is related to the molecular weight, and hence the viscosity, of the HA molecules injected.
Schwartz DM, Equi R, Jumper M. Coinjection of Hyaluronic Acid and Hyaluronidase. Arch Ophthalmol. 2000;118(3):445. doi:
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