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P.A. Quiram, V. Leverenz, R. Baker, L. Dang, M.T. Trese, F.J. Giblin; Enzymatic Manipulation of the Vitreous Cavity by Microplasmin Affects Vitreous Oxygen Levels in Animal Models . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1486.
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To determine if induction of an enzymatic–assisted posterior vitreous detachment (PVD) and vitreous liquefaction affects O2 concentration in the vitreous cavity.
Either microplasmin (0.6 units) or hyaluronidase (25 units) was injected intravitreally into either guinea pigs or Brown Norway rats with the contralateral eye as a control. One week post injection, vitreal oxygen concentration was measured using a highly sensitive, platinum–based fluorophore O2 sensor (Oxford Optronix, Ltd.). In addition, control and microplasmin–injected animals were exposed to 100% oxygen by facemask, and vitreal O2 levels were measured over time. Scanning electron microscopy (SEM) was used to evaluate the vitreoretinal interface for the presence of a PVD.
Intravitreal injection of microplasmin significantly increased vitreal O2 concentration in guinea pigs (4–fold, p<0.05) and rats (2–fold, p<0.005) as compared to control eyes. Intravitreal injection of PBS or hyaluronidase revealed similar vitreal O2 levels as compared to controls. When the normal, control guinea pig was exposed to 100% O2 the mid–vitreal levels of O2 steadily increased to 55 mm Hg over 20 minutes with a slow return to baseline when switched to room air. When exposed to 100% O2, microplasmin–treated eyes showed an accelerated increase in oxygen levels reaching 80 mm Hg in 2 minutes. The results suggest that an intact vitreous cavity may act as a buffer against elevated blood oxygen levels. SEM showed smooth retinal surfaces in microplasmin–injected eyes, indicating the presence of a PVD which was not present in control eyes.
Our results suggest that enzymatic–assisted PVD with microplasmin may increase vitreal O2 levels and increase O2 exchange within the vitreous cavity.
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