title: Retinal oxygen: from animals to humans.
abstract: This article discusses retinal oxygenation and retinal metabolism by focusing on measurements made with two of the principal methods used to study O2in the retina: measurements of PO2with 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 O2concentration in retinal vessels. Microelectrodes uniquely have high spatial resolution, allowing the mapping of PO2in 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.
authors.affiliation: Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Neurobiology Department, Northwestern University, 2205 Tech Drive, Evanston 60208-3520, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA. Electronic address: r-linsenmeier@northwestern.edu.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Linsenmeier
authors.affiliation: Biomedical Engineering Department, Northwestern University, 2145 Sheridan Road, Evanston 60208-3107, IL, USA; Ophthalmology Department, Northwestern University, 645 N. Michigan Ave, Suite 440, Chicago 60611, IL, USA. Electronic address: hfzhang@northwestern.edu.
authors.forename: Hao F
authors.initials: HF
authors.lastname: Zhang
mesh_terms: D000818:Animals; D003623:Dark Adaptation; D006801:Humans; D010100:Oxygen / Q000378:metabolism*; D012039:Regional Blood Flow; D012160:Retina / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D012164:Retinal Diseases / Q000175:diagnosis / Q000378:metabolism / Q000503:physiopathology
chemical_list: D010100:Oxygen
keywords: Animal; Diabetes; Human; Hyperoxia; Hypoxia; Macular degeneration; Oximetry; Oxygen; Oxygen microelectrode; Retina; Retinal detachment; Retinal metabolism