Oxygen Measurements in Animals

Linsenmeier, Robert A.

doi:10.1007/978-3-540-69469-4_4

Cited by 6 publications

(10 citation statements)

References 177 publications

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“…32 On the other hand, 100% oxygen exposure increased inner retinal and vitreous PO 2 by a factor of 3 in cats (»20-60 mm Hg), a change regulated in part by large increases in choroidal PO 2 (»80-240 mm Hg). 33,34 As a first approximation, these experimental studies provide a PO 2 perturbation window for the hypoxia and hyperoxia simulations (up to a factor of 3).…”

Section: Oxygen Supply From the Inner Retina (But Not The Aqueous Humor)mentioning

confidence: 99%

Computational Model for Oxygen Transport and Consumption in Human Vitreous

Filas

Shui

Beebe

2013

Invest. Ophthalmol. Vis. Sci.

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Section: Oxygen Supply From the Inner Retina (But Not The Aqueous Humor)mentioning

confidence: 99%

Computational Model for Oxygen Transport and Consumption in Human Vitreous

Filas

Shui

Beebe

2013

Invest. Ophthalmol. Vis. Sci.

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“…Retinal O 2 is an enormous topic, and no review can completely cover it. There are several excellent sources for information on the related topic of ocular blood flow (Pemp and Schmetterer, 2008; Pournaras et al, 2008; Schmetterer and Kiel, 2012), and the reader is also referred to earlier reviews for different aspects of retinal oxygenation and metabolism (Hardarson, 2013; Linsenmeier, 2010, 2012; Wangsa-Wirawan and Linsenmeier, 2003; Yu and Cringle, 2001). Yu and Cringle (Yu and Cringle, 2001) paid particular attention to avascular retinas.…”

Section: Importance Of the Oxygen Supply To The Retinamentioning

confidence: 99%

“…One can take several approaches to measuring O 2 in the retina in vivo (Harris et al, 2003; Hogeboom van Buggenum et al, 1996; Linsenmeier, 2012). These include i) measurements of phosphorescence lifetime of an intravascular (or more recently extravascular) porphyrin-based dye whose lifetime is inversely proportional to the local PO 2 (Shahidi et al, 2006; Shahidi et al, 2010), ii) MRI measurements of relative PO 2 (Berkowitz, 1996; Berkowitz et al, 2001; Cheng et al, 2006), iii) optical probes using dyes embedded on the surface of a fiberoptic probe (Holekamp et al, 2005; Stefansson et al, 1989), and iv) histological measurements with a chemical probe, pimonidazole, that labels hypoxic regions (de Gooyer et al, 2006; Wright et al, 2010).…”

Section: Approaches To Retinal Oxygenmentioning

confidence: 99%

“…The temporal response of oxygen microelectrodes is also very fast, a few msec (Schneiderman and Goldstick, 1978), which is much faster than any PO 2 changes due to metabolism. Oxygen electrodes do consume O 2 , but at a current of 6 pA, which is typical, one can calculate that this is only about the amount that one retinal neuron uses (Linsenmeier, 2012), so they are not thought to markedly disturb tissue PO 2 . Because O 2 is normally the only substance that undergoes net reduction in tissue, the current is purely due to O 2 , unlike electrodes that operate in the oxidizing direction, where one has to separate signals from several compounds that are oxidized at the electrode (e.g.…”

Section: Approaches To Retinal Oxygenmentioning

confidence: 99%

“…Comparative measurements of QO 2 from microelectrodes and other methods can be found in the same references as well as in (Linsenmeier, 2012). …”

Section: Fundamentals Of O2 Supply To the Retinamentioning

confidence: 99%

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Retinal oxygen: from animals to humans

Linsenmeier

Zhang

2017

Progress in Retinal and Eye Research

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192

150

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This article discusses retinal oxygenation and retinal metabolism by focusing on measurements made with two of the principal methods used to study O2 in the retina: measurements of PO2 with oxygen-sensitive microelectrodes in vivo in animals with a retinal circulation similar to that of humans, and oximetry, which can be used non-invasively in both animals and humans to measure O2 concentration in retinal vessels. Microelectrodes uniquely have high spatial resolution, allowing the mapping of PO2 in detail, and when combined with mathematical models of diffusion and consumption, they provide information about retinal metabolism. Mathematical models, grounded in experiments, can also be used to simulate situations that are not amenable to experimental study. New methods of oximetry, particularly photoacoustic ophthalmoscopy and visible light optical coherence tomography, provide depth-resolved methods that can separate signals from blood vessels and surrounding tissues, and can be combined with blood flow measures to determine metabolic rate. We discuss the effects on retinal oxygenation of illumination, hypoxia and hyperoxia, and describe retinal oxygenation in diabetes, retinal detachment, arterial occlusion, and macular degeneration. We explain how the metabolic measurements obtained from microelectrodes and imaging are different, and how they need to be brought together in the future. Finally, we argue for revisiting the clinical use of hyperoxia in ophthalmology, particularly in retinal arterial occlusions and retinal detachment, based on animal research and diffusion theory.

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Coupling blood flow and neural function in the retina: a model for homeostatic responses to ocular perfusion pressure challenge

Lim

Nguyen

et al. 2013

Physiol Rep

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Retinal function is known to be more resistant than blood flow to acute reduction of ocular perfusion pressure (OPP). To understand the mechanisms underlying the disconnect between blood flow and neural function, a mathematical model is developed in this study, which proposes that increased oxygen extraction ratio compensates for relative ischemia to sustain retinal function. In addition, the model incorporates a term to account for a pressure-related mechanical stress on neurons when OPP reduction is achieved by intraocular pressure (IOP) elevation. We show that this model, combining ocular blood flow, oxygen extraction ratio, and IOP mechanical stress on neurons, accounts for retinal function over a wide range of OPP manipulations. The robustness of the model is tested against experimental data where ocular blood flow, oxygen tension, and retinal function were simultaneously measured during acute OPP manipulation. The model provides a basis for understanding the retinal hemodynamic responses to short-term OPP challenge.

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Oxygen Measurements in Animals

Cited by 6 publications

References 177 publications

Computational Model for Oxygen Transport and Consumption in Human Vitreous

Computational Model for Oxygen Transport and Consumption in Human Vitreous

Retinal oxygen: from animals to humans

Coupling blood flow and neural function in the retina: a model for homeostatic responses to ocular perfusion pressure challenge

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