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.