Changes in vitreal oxygen tension distribution in the streptozotocin diabetic rat

Abstract

Measurements of vitreal oxygen tension have been made for the first time in the streptozotocin-induced diabetic rat eye. A total of 36 Sprague Dawley rats were divided into a control (n = 18) and streptozotocin injected group (n = 18), and after 5-6 weeks of established hyperglycaemia, an acute experiment was performed in which vitreal oxygen tension profiles were determined with oxygen sensitive microelectrodes. The control rats had significant oxygen tension gradients in the vitreous close to retinal arteries with relatively flat oxygen tension profiles close to retinal veins and intermediate regions. All control rats had a substantial arteriovenous oxygen tension difference when measurements were made on retinal arteries and veins. In contrast the oxygen tension profiles measured in the vitreous of streptozotocin rats showed markedly reduced oxygen gradients in the vicinity of retinal arteries and a smaller arteriovenous oxygen tension difference. In both groups of rats, for distances of 500 microns and greater from the retina (mid vitreous) a plateau oxygen tension value was observed. No significant difference was found in this mean mid vitreous value between the control rats and diabetic rats under the same systemic conditions. We conclude that there are significant changes in oxygen tension near retinal arteries in streptozotocin-induced diabetes before any histopathological changes are evident.

MRI of rod cell compartment-specific function in disease and treatment in vivo

“…If this assumption is true, retinal hypoxia should precede the appearance of neovascularization. However, magnetic resonance studies did not find evidence to support a special early role of retinal hypoxia in proliferative retinopathy models, a conclusion in-line with that of other labs (Alder et al, 1991;Berkowitz, 2008;Diederen et al, 2006;Lau and Linsenmeier, 2014;Ola et al, 2006;Reeves et al, 2002;Wanek et al, 2014;Wright et al, 2011;Zhang et al, 2003).…”

Retinal Vessel Oxygen Saturation under Flicker Light Stimulation in Patients with Nonproliferative Diabetic Retinopathy

“…29 In the same animal model, Alder et al found a markedly decreased arteriovenous pO 2 difference compared to control rats, but no difference in the vitreous oxygen tension. 10 However, the vitreous pO 2 increase upon pure oxygen inhalation, measured by magnetic resonance imaging, was higher in patients with type 1 diabetes than in controls. 30 This may be explained by a dysfunction of the blood flow regulation, which is unable to reduce the blood flow sufficiently in case of hyperoxia.…”

“…[2][3][4][5][6] Linsenmeier et al found a reduced oxygen partial pressure (pO 2 ) in the inner retina of diabetic cats. 7 Whereas the pO 2 in the vitreous cavity was not affected by experimental diabetes in other animal models, [8][9][10] it was decreased in patients undergoing vitrectomy, 11 but higher over retinal areas treated with laser photocoagulation than over non-treated areas. 12 In contrast to pO 2 , the hemoglobin oxygen saturation (SO 2 ) can be assessed non-invasively by spectroscopic techniques.…”

Diabetic patients with retinopathy show increased retinal venous oxygen saturation

“…This may reflect either a reduced oxygen demand by the coagulated tissue, or an increase of oxygen diffusion from the choroid to the inner retina, or both [37]. Taken together, these investigations suggest that the development of retinopathy may be linked to the partial pressure of oxygen (pO 2 ) in the outer retina [1,10,25,32,34]. This can be measured with oxygen-sensitive electrodes or fiberoptic probes; this, however, is an invasive procedure not suitable for clinical diagnostics.…”