Response to the letter to the editor: Venous oxygen saturation is reduced and variable in central retinal vein occlusion

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Retinal Vessel Oxygen Saturation during 100% Oxygen Breathing in Healthy Individuals.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.To detect how systemic hyperoxia affects oxygen saturation in retinal arterioles and venules in healthy individuals.Retinal vessel oxygen saturation was measured in 30 healthy individuals with a spectrophotometric retinal oximeter (Oxymap T1). Oximetry was performed during breathing of room air, 100% oxygen (10 minutes, 6L/min) and then again room air (10 minutes recovery).Mean oxygen saturation rises modestly in retinal arterioles during 100% oxygen breathing (94.5%±3.8 vs. 92.0%±3.7% at baseline, p<0.0001) and dramatically in retinal venules (76.2%±8.0% vs. 51.3%±5.6%, p<0.0001). The arteriovenous difference decreased during 100% oxygen breathing (18.3%±9.0% vs. 40.7%±5.7%, p<0.0001). The mean diameter of arterioles decreased during 100% oxygen breathing compared to baseline (9.7±1.4 pixels vs. 10.3±1.3 pixels, p<0.0001) and the same applies to the mean venular diameter (11.4±1.2 pixels vs. 13.3±1.5 pixels, p<0.0001).Breathing 100% oxygen increases oxygen saturation in retinal arterioles and more so in venules and constricts them compared to baseline levels. The dramatic increase in oxygen saturation in venules reflects oxygen flow from the choroid and the unusual vascular anatomy and oxygen physiology of the eye.Icelandic Centre for Research 100429021 Landspitali-University Hospital Research Fund A-2013-023 Icelandic Fund for Prevention of Blindnes

Venous oxygen saturation is reduced and variable in central retinal vein occlusion.

To access publisher's full text version of this article click on the hyperlink at the bottom of the pageTo estimate the presence and variability of retinal hypoxia in patients with central retinal vein occlusion (CRVO).Hemoglobin oxygen saturation was measured in retinal vessels of both eyes in 14 patients with unilateral CRVO. The noninvasive spectrophotometric retinal oximeter is based on a fundus camera and simultaneously captures two images at 570 nm and 600 nm wavelengths. Five of the patients were followed with repeated retinal oximetry images over time.The mean oxygen saturation in retinal venules was 31 % ±12 % in CRVO eyes and 52 % ±11 % in unaffected fellow eyes (mean ±SD, n = 14, p < 0.0001). The arteriovenous difference was 63 % ±11 % in eyes with CRVO and 43 % ±7 % in fellow eyes (p < 0.0001). The variability of retinal venous oxygen saturation was substantial within and between eyes affected by CRVO. Venular oxygen saturation improved with treatment and over time in all five patients that were followed.CRVO eyes are hypoxic compared to fellow eyes and arteriovenous difference in hemoglobin oxygen saturation is increased. This is consistent with tissue hypoxia resulting from reduced blood flow. Further studies are needed to understand the correlation between hypoxia, severity of disease and prognosis.Icelandic Fund for Prevention of Blindness Icelandic Center for Research (Rannis) University of Iceland Research Fund Landspitali-University Hospital Research Fund A-2013-041 A-2014-033 Memorial Fund of Helga Jonsdottir and Sigurlidi Kristjansson Icelandic Nurses' Research and Science Fund Icelandic Nurses' Association Science Found Kristin Thoroddsen Memorial Fun

John Clarke (Fred Dagg), Windsor, Melbourne, 1982 [picture] /

Title from inscriptions on verso.; Part of collection: Rennie Ellis: Aussies all.; Inscriptions: titled, "1982/2006" and "Aussies All Exhibition"--In ink lower right on verso.; Item with accompanying exhibition note.; Condition: Good.; Also available in electronic version via the Internet at: http//nla.gov.au/nla.pic-vn4083978; Purchased from Rennie Ellis Photographic Archive through Josef Lebovic Gallery, 2007.; Exhibited: Rennie Ellis: Aussies all, National Portrait Gallery, Canberra, 2006. AuCNL

Physiological variables that were measured (mean± SD) during room air breathing (Baseline), 100% oxygen breathing and 10 minutes of room air breathing subsequent to 100% oxygen breathing (Recovery).

<p>EtCO₂, end tidal carbon dioxide; HR, heart rate; IOP, intraocular pressure; BP, blood pressure; MAP, mean arterial pressure; OPP, ocular perfusion pressure; SpO₂, finger oxygen saturation.</p><p>Physiological variables that were measured (mean± SD) during room air breathing (Baseline), 100% oxygen breathing and 10 minutes of room air breathing subsequent to 100% oxygen breathing (Recovery).</p

Retinal vessel oxygen saturation in arterioles and venules; before 100% oxygen breathing (baseline), during 100% oxygen breathing and 10 minutes after 100% oxygen breathing (recovery) in healthy individuals (n = 30).

<p>The lines show mean values for each group. Each point denotes value from one individual.</p

Retinal vessel oxygen saturation during baseline, 100% oxygen breathing and recovery (10 minutes of room air breathing after 100% oxygen breathing).

<p>The p-values show statistical difference between baseline and 100% oxygen breathing (Student´s t-test).</p><p>Retinal vessel oxygen saturation during baseline, 100% oxygen breathing and recovery (10 minutes of room air breathing after 100% oxygen breathing).</p

A pseudocolor fundus map of oxygen saturation during A. Baseline (room air breathing), B. 100% oxygen breathing for ten minutes and C. Recovery (room air breathing for 10 minutes after 100% oxygen breathing).

<p>Red color denotes oxygen saturation approximately 90–100% and green color denotes oxygen saturation approximately 50–60% (see scale on right side of each image).</p