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I.K. Petropoulos, J.–A.C. Pournaras, A.N. Stangos, C.J. Pournaras; Preretinal Partial Pressure of Oxygen Gradients Before and After Experimental Pars Plana Vitrectomy . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4665.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the preretinal partial pressure of oxygen (PO2) gradients before and after experimental pars plana vitrectomy, as it has been supported that following vitrectomy, PO2 in the vitreous cavity significantly increases for prolonged periods.
Preretinal PO2 was measured in 6 anesthetized miniature pigs using oxygen–sensitive microelectrodes (10–µm tip diameter) introduced into the vitreous cavity using an electronic micromanipulator. Arterial, venous, and intervascular preretinal PO2 gradients were recorded during slow withdrawal of the microelectrode from the vitreoretinal interface (zero position) to a distance of 2 mm in the vitreous. Gradient recordings were repeated over the same territories after standard pars plana vitrectomy and perfusion with balanced salt solution (BSS).
Before vitrectomy, arterial, venous, and intervascular preretinal PO2 at zero position were 59.4±13.2 mmHg (n=12), 22.4±3.4 mmHg (n=10), and 18.0±5.9 mmHg (n=7), respectively. Distinct PO2 gradients between those three locations were recorded within the first 500 µm from the vitreoretinal interface; beyond that distance no distinct gradients existed, and PO2 at 2 mm from the vitreoretinal interface was 28.2±3.3 mmHg (n=29). Immediately after vitrectomy and during continuous perfusion with BSS, arterial, venous, and intervascular preretinal PO2 at zero position significantly increased to 99.8±12.2 mmHg (n=6), 48.9±19.0 mmHg (n=6), and 62.6±23.1 mmHg (n=6), respectively. PO2 at 2 mm from the vitreoretinal interface was much higher, 174.5±16.6 mmHg (n=18), indicating a gradient from the vitreous cavity towards all preretinal measured sites. When continuous perfusion with BSS was interrupted, PO2 at 2 mm from the vitreoretinal interface decreased to 36.2±2.8 mmHg (n=5) 2 1/2 hours later, slightly elevated than before vitrectomy, indicating progressive reversal of PO2 gradients in the vitreous cavity towards the pre–vitrectomy ones.
PO2 gradients are still present close to the retina after pars plana vitrectomy and during continuous perfusion with BSS, indicating oxygen diffusion from the vitreous cavity towards the retina. Following vitrectomy, PO2 in the vitreous cavity increases significantly during continuous perfusion with BSS due to the high PO2 in the latter, as it is equilibrated with atmospheric air. However, when the perfusion with BSS is interrupted, rapid reversal towards the pre–vitrectomy oxygen distribution in the vitreous cavity is established within 2 1/2 hours.
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