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U. Pinninti, S. Mansour; Effects of Ovine Hyaluronidase on Scleral Permeability . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5106.
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The aim of these experiments is to establish an effective dose range for ovine hyaluronidase (Vitrase® ISTA Pharmaceuticals), and determine the extent of increased penetration of relevant therapeutic drugs (eg. Macugen, Kenalog, Avastin) when used with Vitrase as a posterior subtenons injection. This would be especially beneficial in the treatment of a variety of vitreoretinopathies such as diabetic retinopathy and age–related macular degeneration, without the use of intravitreal injections. Also, determining the concentrations of medications in the vitreous and correlating this with treatment outcomes would be useful in determining their optimal dosage.
36 enculeated calf eyes are incubated in Vitrase and stained with dye. The posterior sclera is examined under the microscope for extent of staining. The concentration of Vitrase and incubation time is varied in order to establish the most effective dose range for Vitrase. In vivo studies in rabbits will follow with mass spectrometry to determine the concentrations of therapeutic drugs (eg. Macugen, Kenalog, Avastin) in the vitreous when administered with Vitrase as a posterior subtenons injection. Subsquently, a human clinical trial will use this optimal Vitrase concentration. The patient population will be diabetics with clinically significant macular edema about to undergo cataract surgery. They receive triamcinolone and vitrase as a posterior sub–tenons injection a week prior to cataract extraction. At the time of cataract extraction a vitreous biopsy is done to determine the concentration of medication. The patients are followed and evaluated for relative effect of triamcinolone as an intravitreal injection versus delivered subtenons with Vitrase.
2 enucleated calf eyes were incubated in methylene blue for durations of 10min and 15min. Posterior sclera was then examined pathologically for the extent of penetration of the dye. It was noted that the dye stained only the outer sclera. We are currently incubating 36 enucleated calf eyes in Vitrase concentrations varying from 1,240 U/ml to 12.4 U/ml, stained with methylene blue, and the sclera examined pathologically. This will identify the lowest effective concentration of drug that penetrates that sclera.
The control level of staining of the sclera has been determined, and will serve as a baseline comparison to evaluate the effects of Vitrase on scleral permeability. Results to follow will reveal vitreous concentrations of medications delivered by subtenons injection with Vitrase and their relative efficacy as compared to intravitreal injections without Vitrase.
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