Corneal toxicity of intraocular hyaluronidase

The purpose of this study was to examine the corneal toxicity of different preparations of intraocular hyaluronidase. SDS-PAGE analysis of bovine testicular hyaluronidase (Wydase) and chromatographically purified hyaluronidase (Sigma) was performed. These two preparations were injected into the anterior chamber of rabbits in amounts ranging from 1.5-150 IU (Wydase) and 1.5-300 IU (Sigma). A third set of rabbit eyes received Wydase vehicle alone or in combination with Sigma hyaluronidase. Treated control eyes were injected with saline. Slit lamp examination and indirect ophthalmoscopy were performed preoperatively and on postoperative days 1 and 7. Light microscopy of the corneas was performed. SDS-PAGE of Wydase revealed numerous protein impurities, while Sigma demonstrated one protein band consistent with mammalian hyaluronidase. Persistent corneal edema, severe anterior chamber fibrin, and endothelial necrosis, were seen in the majority of eyes injected with Wydase in amounts of 50 IU and greater (n = 11). Thirty percent (30%) of the eyes injected with the Sigma preparation (n = 11) had localized corneal opacity similar to 50% of eyes injected with saline (n = 2). Of the rabbit eyes injected with the Wydase vehicle (n = 19), 68% had toxic changes. Intracameral injection of Wydase is toxic to the rabbit cornea in amounts of 50 IU and greater. A chromatographically purified preparation showed only transient local toxicity. Toxicity of Wydase may be due to protein impurities and the thimerosal-containing vehicle.