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 and vessel diameter in retinitis pigmentosa.

To access publisher's full text version of this article click on the hyperlink at the bottom of the pageTo assess retinal vessel oxygen saturation and retinal vessel diameter in retinitis pigmentosa.A retinal oximeter (Oxymap ehf., Reykjavik, Iceland) was used to measure retinal vessel oxygen saturation and vessel diameter in ten patients with retinitis pigmentosa (RP) (mean age 49 years, range 23-71 years). Results were compared with age- and gender-matched healthy individuals. All patients had advanced stage of the disease with visual fields restricted to the macular region.Oxygen saturation in retinal venules was 58.0 ± 6.2% in patients with RP and 53.4 ± 4.8% in healthy subjects (p = 0.017). Oxygen saturation in retinal arterioles was not significantly different between groups (p = 0.65). The mean diameter of retinal arterioles was 8.9 ± 1.6 pixels in patients with RP and 11.4 ± 1.2 in healthy controls (p < 0.0001). The corresponding diameters for venules were 10.1 ± 1.2 (RP) and 15.3 ± 1.7 (healthy, p < 0.0001).Increased venous saturation and decreased retinal vessel diameter suggest decreased oxygen delivery from the retinal circulation in retinitis pigmentosa. This is probably secondary to tissue atrophy and reduced oxygen consumption

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

Moreton 20 chain map. Sheet 31A [cartographic material].

Cadastral map of the Moreton Bay area, Queensland.; Also available in an electronic version via the internet at: http://nla.gov.au/nla.map-rm2014-20

Comparison of arteriole, venule and arteriole-venule (A-V) oxyhemoglobin saturation difference between the total group of COPD subjects and healthy controls breathing ambient air.

<p>All values are presented as mean ± standard deviation. *Significant difference between COPD patients and healthy controls.</p

Pseudocolour oximetry images of a retina.

<p>A. Pseducolour image of a retina with the optic disc centered in a healthy subject. Vessel segments between the two circles are selected for analysis. The colours indicate oxyhemoglobin saturation as seen on the scale on the right. In general, arterioles are orange to red, indicating oxyhemoglobin saturation of about 90–100%. Venules may vary from blue to yellow but are normally green, indicating oxyhemoglobin saturation of approximately 50–60%. B. Retinal vessel oxyhemoglobin saturation in a patient with severe COPD after 10 minutes of ambient air breathing. The oximetry image indicates hypoxia of retinal arterioles and venules.</p

Retinal oximetry measures systemic hypoxia in central nervous system vessels in chronic obstructive pulmonary disease

<div><p>Background</p><p>Determination of the blood oxyhemoglobin saturation in the retinal vessels of the eye can be achieved through spectrophotometric retinal oximetry which provides access to the state of oxyhemoglobin saturation in the central nervous system circulation. The purpose of this study was to test the capability of the Oxymap T1 oximeter to detect systemic hypoxemia and the effect of supplemental oxygen on retinal vessel oxyhemoglobin saturation.</p><p>Methods</p><p>Oxygen saturation of hemoglobin in retinal arterioles and venules was measured in 11 subjects with severe chronic obstructive pulmonary disease (COPD) on long term oxygen therapy. Measurements were made with and without their daily supplemental oxygen. Eleven healthy age and gender matched subjects were measured during ambient air breathing for comparison of oxyhemoglobin saturation in retinal arterioles and venules. Retinal arteriolar oxyhemoglobin saturation in COPD subjects inspiring ambient air was compared with finger pulse oximetry and blood samples from radial artery.</p><p>Results</p><p>COPD subjects had significantly lower oxyhemoglobin saturation during ambient air breathing than healthy controls in both retinal arterioles (87.2%±4.9% vs. 93.4%±4.3%, p = 0.02; n = 11) and venules (45.0%±10.3% vs. 55.2%±5.5%, p = 0.01). Administration of their prescribed supplemental oxygen increased oxyhemoglobin saturation in retinal arterioles (87.2%±4.9% to 89.5%±6.0%, p = 0.02) but not in venules (45.0%±10.3% to 46.7%±12.8%, p = 0.3). Retinal oximetry values were slightly lower than radial artery blood values (mean percentage points difference = -5.0±5.4, 95% CI: -15.68 to 5.67) and finger pulse oximetry values (-3.1±5.5, 95% CI: -14.05 to 7.84).</p><p>Conclusions</p><p>The noninvasive Oxymap T1 retinal oximetry detects hypoxemia in central nervous system vessels in patients with severe COPD compared with healthy controls. The instrument is sensitive to changes in oxygen breathing but displays slightly lower measures than finger pulse oximetry or radial artery measures. With further technological improvement, retinal oximetry may offer noninvasive “on-line” measurement of oxygen levels in central circulation in general anesthesia and critically ill patients.</p></div

Comparison of percent (%) oxyhemoglobin saturation between retinal vessels, finger pulse oximetry and radial artery blood with and without supplemental oxygen therapy in 10 patients with severe COPD.

<p>Arteriole and venule oxyhemoglobin saturation difference and diameters are also shown.</p