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P. A. Quiram, V. Leverenz, R. Baker, D. Loan, M. Trese, F. Giblin; Enzymatic Induction of a Posterior Vitreous Detachment Alters Molecular Vitreodynamics in Animal Models. Invest. Ophthalmol. Vis. Sci. 2007;48(13):83.
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To determine if induction of an enzymatic-assisted posterior vitreous detachment (PVD) and vitreous liquefaction affects levels of molecular oxygen, VEGF and ascorbate in animal models.
Either microplasmin (0.6 units) or hyaluronidase (25 units) was injected intravitreally into one eye of either guinea pigs, Brown Norway rats, rabbits or cats with the contralateral eye used as a control. One week post injection, vitreal oxygen concentrations were measured using a highly sensitive, platinum-based fluorophore Oxylab oxygen sensor. Immediately post mortem, anterior chamber and vitreous levels of ascorbate and VEGF levels were measured. Scanning electron microscopy (SEM) was used to assess the vitreoretinal interface for the presence of a PVD.
Intravitreal injection of microplasmin significantly increased the vitreal oxygen concentration in and rats (35 mm Hg vs. 23 mmHg for the control; p<0.001) and cats (26.2 mm Hg vs. 16.3 mm Hg for the control; p<0.001). In contrast, intravitreal injection of hyaluronidase (vitreous liquefaction without induction of a PVD) did not significantly increase vitreal oxygen levels. Upon exposure to 100% oxygen by facemask, microplasmin injected eyes showed a rapid increase in vitreal oxygen levels compared to hyaluronidase injected eyes and controls, indicating that the presence of a PVD allows rapid oxygen exchange within the vitreous cavity. Following injection of microplasm in rabbits, ascorbate levels increased in the vitreous cavity compared to controls (0.91 mmoles vs 0.54 mmoles, respectively p=0.032). Changes to VEGF following injection of microplasmin and hyaluraronidase are currently underway. SEM showed smooth retinal surfaces in microplasmin injected eyes, indicating presence of a PVD which was not present in control or hyaluronidase injected eyes.
Our results suggest that enzymatic-assisted PVD with microplasmin alters molecular vitreodynamics by increasing O2 levels and increasing the rate of O2 exchange within the vitreous cavity.
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