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

Background 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. Methods 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. Results 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). Conclusions 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.This study was funded by the Icelandic Fund for Prevention of Blindness, The Icelandic Center for Research (Rannı´s), University of Iceland, Landspitali-University Hospital Research Fund A- 2013-041 & A-2014-033, Memorial Fund of Helga Jonsdottir and Sigurlidi Kristjansson.Peer Reviewe

Súrefnismælingar í augnbotnum

Purpose Malfunction of retinal blood flow or oxygenation is believed to be involved in various diseases. Among them are retinal vessel occlusions, diabetic retinopathy and glaucoma. Reliable, non-invasive technology for retinal oxygen measurements has been scarce and most of the knowledge on retinal oxygenation comes from animal studies. This thesis describes human retinal oximetry, performed with novel retinal oximetry technology. The thesis describes studies on retinal vessel oxygen saturation in (1) light and dark in healthy volunteers, (2) central retinal vein occlusion, (3) branch retinal vein occlusion, (4) central retinal artery occlusion, (5) diabetic retinopathy, (6) patients undergoing glaucoma surgery and (7) patients taking glaucoma medication. Methods The retinal oximeter (Oxymap ehf., Reykjavik, Iceland) is based on a fundus camera. An attached image splitter allows the simultaneous capture of four images of the same area of the fundus. Two images are used for further analysis, one acquired with 586 nm light and one with 605 nm light. Light absorbance of retinal vessels is sensitive to oxygen saturation at 605 nm but not at 586 nm. Measurement of reflected light at these wavelengths allows estimation of oxygen saturation in the main retinal vessels. This is performed with custom-made analysis software. Results Light and dark: After 30 minutes in the dark, oxygen saturation in retinal arterioles of healthy volunteers was 92±4% (mean±SD, n=15). After 5 minutes in 80 cd/m2 light, the arteriolar saturation was 89±5%. The decrease was statistically significant (p=0.008). The corresponding values for retinal venules were 60±5% in the dark and 55±10% in the light (p=0.020). Similar results were found after alternating 5 minute periods of darkness and light. In a second experiment (n=19), a significant decrease in retinal vessel oxygen saturation was found in 100 cd/m2 light compared to darkness but 1 and 10 cd/m2 light had no significant effect. Central retinal vein occlusion: In patients with central retinal vein occlusion, the mean saturation in affected retinal venules was 49±12%, while the mean value for venules in the fellow eye was 65±6% (mean±SD, p=0.003, n=8). The retinal arteriolar saturation was the same in affected (99±3%) and the unaffected (99±6%) eyes. The venous oxygen saturation showed much variation between affected eyes. Branch retinal vein occlusion: Median oxygen saturation in venules affected by branch retinal vein occlusion was 59% (range 12-93%, n=22), while it was 63% (23-80%) in unaffected venules in the affected eye and 55% (39-80%) in venules in the fellow eye. The difference was not statistically significant (p>0.05). There was a significant difference between affected arterioles (median 101%, range 89-115%) and unaffected arterioles (95%, 85-104%) in the affected eye (p<0.05, n=18). Central retinal artery occlusion: In a patient with a day’s history of central retinal artery occlusion due to temporal arteritis, the mean arteriolar saturation was 71±9% and 63±9% in the venules. One month later, after treatment with prednisolone, the mean arteriolar saturation was 100±4% and the venous saturation 54±5%. Diabetic retinopathy: When compared with healthy volunteers (n=31), patients with all categories of diabetic retinopathy had on average 7-10 percentage points higher saturation in retinal arterioles (p<0.05 for all categories, n=6-8 in each category). In venules, the saturation was 8-12 percentage points higher (p<0.05 for all categories). Glaucoma surgery: Oxygen saturation in retinal arterioles increased by 2 percentage points on average (p=0.046, n=19) with surgery, which lowered intraocular pressure from 23±7 mmHg (mean±SD) to 10±4 mmHg (p0.35). Dorzolamide: A significant reduction of 3 percentage points was found in arterioles (p0.05, n=7). Conclusions Dual wavelength oximetry can be used to non-invasively measure retinal vessel oxygen saturation in health and disease. The results indicate that retinal vessel oxygen saturation is (1) increased in the dark, (2) lower in venules affected by central retinal vein occlusions, (3) variable in branch retinal vein occlusion, (4) lower in retinal arterioles in central retinal artery occlusion, (5) increased in diabetic retinopathy, (6-7) mildly affected by glaucoma surgery or dorzolamide.Tilgangur Talið er að truflun á blóðflæði í sjónhimnuæðum og / eða truflun á súrefnisbúskap sjónhimnu tengist ýmsum sjúkdómum, þar á meðal æðalokunum í sjónhimnu, sjónhimnusjúkdómi í sykursýki og gláku. Áreiðanleg tækni til mælinga á súrefnisbúskap sjónhimnu án inngrips hefur verið af skornum skammti og því byggir þekkingin að stórum hluta á dýratilraunum. Í þessari ritgerð er lýst rannsóknum á súrefnismettun í sjónhimnuæðum (1) í ljósi og myrkri í heilbrigðum sjálfboðaliðum, (2) í miðbláæðarlokun í sjónhimnu, (3) í bláæðagreinarlokun í sjónhimnu, (4) í miðslagæðarlokun í sjónhimnu, (5) í sjónhimnusjúkdómi í sykursýki, (6) í sjúklingum, sem undirgengust skurðaðgerð vegna gláku og (7) í sjúklingum sem tóku glákulyf. Aðferðir Súrefnismælirinn (Oxymap ehf., Reykjavík) er byggður á augnbotnamyndavél. Við augnbotnamyndavélina er festur mynddeilir, sem gerir kleift að ná fjórum myndum af sama svæði augnbotns samtímis. Tvær myndanna eru notaðar til frekari vinnslu, ein er tekin með 586 nm ljósi en hin með 605 nm ljósi. Ljósgleypni sjónhimnuæða er næm fyrir súrefnismettun við 605 nm en ekki við 586 nm. Meta má súrefnismettun í aðal sjónhimnuæðunum með því að mæla ljósendurkast á þessum tveimur bylgjulengdum. Þetta er gert með aðstoð sérskrifaðs hugbúnaðar. Niðurstöður Ljós og myrkur: Eftir 30 mínútur í myrkri var súrefnismettun í slagæðlingum í sjónhimnu heilbrigðra sjálfboðaliða 92±4% (meðaltal±staðalfrávik, n=15). Eftir 5 mínútur í 80 cd/m2 ljósi, var mettunin í slagæðlingunum marktækt minni eða 89±5% (p=0,008). Samsvarandi gildi fyrir bláæðlinga í sjónhimnu voru 60±5% í myrkri og 55±10% í ljósi (p=0,020). Sambærilegar niðurstöður fengust þegar mælt var eftir 5 mínútna ljós eða myrkur tímabil til skiptis. Í annarri tilraun (n=19) mældist marktækt minni súrefnismettun í sjónhimnuæðlingum í 100 cd/m2 ljósi en í myrkri. Ljós af styrknum 1 eða 10 cd/m2 hafði engin marktæk áhrif. Miðbláæðarlokun í sjónhimnu: Súrefnismettun í bláæðlingum framan við miðbláæðarlokunina var 49±12% (með¬al¬tal±staðalfrávik, n=8). Meðalgildið í bláæðlingunum í hinu auganu var 65±6% (p=0,003). Súrefnismettun í slagæðlingum var 99±3% í sjúka auganu en 99±6% í hinu auganu. Mettun í bláæðlingum var mjög breytileg milli sjúkra augna. Bláæðagreinarlokun í sjónhimnu: Miðgildi súrefnismettunar í bláæðlingum, sem urðu fyrir áhrifum af bláæða¬greinarlokun, var 59% (bil 12-93%, n=22). Miðgildið var 63% (23-80%) í þeim bláæðlingum í sjúka auganu, sem ekki urðu fyrir áhrifum af lokuninni, og 55% (39-80%) í bláæðlingum hins augans. Munurinn var ómarktækur (p>0,05). Marktækur munur var milli slagæðlinga, sem urðu fyrir áhrifum af lokun (miðgildi 101%, bil 89-115%) og slagæðlinga í sama auga, sem ekki urðu fyrir áhrifum af lokun (95%, 85-104%, p<0,05, n=18). Miðslagæðarlokun í sjónhimnu: Meðaltal súrefnismettunar í slagæðlingum sjúklings með eins dags sögu um miðslagæðarlokun var 71±9% en meðaltal í bláæðlingum var 63±9%. Einum mánuði síðar og eftir meðferð með prednisólon var meðaltal súrefnismettunar 100±4% í slagæðlingum og 54±5% í bláæðlingum. Sjónhimnusjúkdómur í sykursýki: Sjúklingar með sjónhimnusjúkdóm í sykursýki (allir flokkar) mældust með að meðaltali 7-10 prósentustigum hærri súrefnismettun í slagæðlingum en heilbrigðir (p<0,05 fyrir alla flokka, n=6-8 í hverjum flokki). Í bláæðlingum var mettunin 8-12 prósentustigum hærri (p<0,05 fyrir alla flokka). Skurðaðgerð við gláku: Súrefnismettun í slagæðlingum sjónhimnu jókst um 2 prósentustig að meðaltali (p=0,046, n=19) eftir aðgerð, sem lækkaði augnþrýsting úr 23±7 mmHg (meðaltal±SD) í 10±4 mmHg (p0,35). Dorsólamíð: Súrefnismettun í slag- og bláæðlingum lækkaði marktækt um 3 prósentustig í slagæðlingum (p0,05, n=7). Ályktanir Nota má tveggja bylgjulengda súrefnismælingu til að mæla súrefnismettun í sjónhimnuæðum án inngrips í heilbrigðum augum og sjúkum. Niðurstöðurnar benda til þess að súrefnismettun (1) hækki í myrkri, (2) sé lægri í bláæðlingum framan við miðbláæðarlokun, (3) sé breytileg í bláæðagreinarlokun, (4) sé lægri í slagæðlingum sjónhimnu við lokun miðslagæðar, (5) hækki í sjónhimnu¬sjúkdómi í sykursýki, (6-7) breytist lítið við glákuaðgerð eða töku dorsólamíðs.Eimskip – University Fund, The Icelandic Center for Research (Rannís), Oxymap ehf., The University of Iceland research fund, The Landspítali-University hospital research fund, Helga Jónsdóttir and Sigurliði Kristjánsson memorial fund, Merck Inc

Glaucomatous visual field loss in eyes undergoing first trabeculectomy in Iceland

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 DownloadINNGANGUR Gláka er hrörnunarsjúkdómur í sjóntaug augans. Eina sannreynda meðferðin við gláku byggir á að lækka augnþrýsting og hægja þannig á hraða sjónsviðsskerðingar. Þegar lyfjameðferð dugir ekki eða gláka er langt gengin er skurðaðgerð beitt. Hjáveituaðgerð er algengasta skurðaðgerðin við gláku. Tilgangur þessarar rannsóknar er að meta alvarleika sjónsviðsskerðingar þegar sjúklingum er vísað í fyrstu hjáveituaðgerð en það hefur ekki verið rannsakað áður á Íslandi. AÐFERÐIR Afturskyggn rannsókn sem nær til allra sjúklinga með gleiðhornagláku sem undirgengust fyrstu hjáveituaðgerð á Íslandi í júní 2014 til mars 2016. Upplýsingar um 86 einstaklinga fengust úr sjúkraskrám. Alvarleiki glákuskemmda var metinn með mean defect (MD) tölugildi á sjónsviðsrannsókn og sjúklingar flokkaðir í þrjá hópa eftir því. NIÐURSTÖÐUR Meðalaldur var 75 ± 11 ár, 57% karlar. Sjúklingar notuðu að meðaltali 3,0 glákulyf við tilvísun í aðgerð og 64% sjúklinganna tóku þrjú lyf eða fleiri. Meðalgildi MD var 13,4 ± 7,7dB (bil: 0,8-26,2 dB), 21% augna höfðu milda sjónsviðsskerðingu (MD12). ÁLYKTUN Augu sem undirgengust hjáveituaðgerð á rannsóknartímabilinu höfðu allt frá mildri til alvarlegrar sjónsviðsskerðingar. Eins og klínískar leiðbeiningar mæla með, virðist meðferð gláku einstaklingsmiðuð og helsta ábending aðgerðar versnun á sjónsviði þrátt fyrir lyfjameðferð. Meðaltal sjónsviðsskerðingar reyndist hærra í okkar rannsókn en í erlendum samanburðarrannsóknum. Augu með alvarlega sjónsviðsskerðingu höfðu að meðaltali lægsta augnþrýstinginn og þynnstu hornhimnuna. Þetta getur bent til þess að mikil áhersla sé lögð á háan augnþrýsting sem ábendingu fyrir aðgerðarþörf en ef til vill of lítil áhersla á sjónsviðsskerðingu og þunna hornhimnu.Introduction: Glaucoma is a degenerative disease in the optic nerve with associated visual field defects (VFD). Trabeculectomy is the most common glaucoma surgery. Surgery is indicated if glaucomatous optic neuropathy progresses despite tolerated medical treatment or in patients with severe VFD. The purpose of this paper is to describe the severity of visual field damage in patients undergoing their first trabeculectomy in Iceland. Methods: A retrospective review of medical records of all patients with open angle glaucoma that underwent first trabeculectomy at Landspítali University Hospital, from June 2013 to March 2016. Visual fields were examined by Octopus automated perimetry and the severity of glaucoma damage was staged according to the mean defect (MD). Results: 86 eyes were included in the study, mean age 75 ± 11 years, 57% men. Patients used on average three IOP lowering medications. Mean MD at referral to surgery was 13.4 ± 7.7dB (min 0.8dB, max 26.2 dB), 21% had early glaucomatous damage (MD < 6dB), 23% moderate (MD 6-12 dB) and 56% severe (MD > 12). Conclusion: VFD at referral to surgery varied from mild VFD to severe damage. Like clinical guidelines recommend, treatment seems to be individualized and the most common indication for surgery was increased VFD despite medical treatment. Mean MD at referral to surgery was high compared to other studies. Eyes with severe VFD had on average lower IOP and thinner cornea. This might indicate that great emphasis is placed on high IOP and perhaps too little emphasis on VFD and cornea thickness.Vísindasjóður Landspítal

Retinal oximetry with a prototype handheld oximeter during hyperoxia

Publisher Copyright: © 2021 The Authors. Acta Ophthalmologica published by John Wiley & Sons Ltd on behalf of Acta Ophthalmologica Scandinavica Foundation.Purpose: Retinal oximetry measures oxygen saturation in retinal vessels. With the introduction of a mobile handheld prototype oximeter, this technique will become available for a broader patient population including bedridden patients and newborn babies. The objective is to determine the sensitivity of this handheld oximeter in room air and during isocapnic hyperoxia. A comparison is made between the handheld oximeter and the Oxymap T1. Methods: Thirteen young healthy subjects with a mean age of 25 ± 2 years were recruited at the Leiden University Medical Center. Retinal oximetry images were acquired during normoxia and during isocapnic hyperoxia for both the prototype oximeter and the OxymapT1. Isocapnic hyperoxia was induced with the dynamic end-tidal forcing technique. For both oximeters, the oxygen saturation and vessel width were measured with Oxymap Analyzer software. The hyperoxic state was verified with blood gas analysis. Results: The mean oxygen saturation measured with the handheld oximeter in arterioles was 91.3% ± 3.9% during normoxia and 94.6% ± 3.9% during hyperoxia (p = 0.001). Oxygen saturation in venules was 56.3% ± 9.8% during normoxia and 82.2 ± 7.4% during hyperoxia (p < 0.001). For the Oxymap T1, the mean oxygen saturation for arterioles was 94.0% ± 2.6% during normoxia and 95.4%±3.2% during hyperoxia (p = 0.004). For the venules, the oxygen saturation was during normoxia 58.9%±3.2% and 84.3 ± 4.0% during hyperoxia (p < 0.001). Conclusion: The handheld retinal oximeter is sensitive to the changes in inhaled oxygen concentration. A small increase in oxygen saturation was measured in the arterioles and a larger increase in the venules. The handheld oximeter gives similar values as the ‘gold standard’ Oxymap T1 oximeter.Peer reviewe

Automation improves repeatability of retinal oximetry measurements

University of Iceland Research Fund (RAK), Icelandic Research Fund (VH), Marie Skłodowska-Curie Actions (SB). Other authors received no funding related to this study (OBO, TSE, SHH). The funders provided support in the form of salaries for authors RAK, VH and SB, but did, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the “author contributions” section. Publisher Copyright: Copyright: © 2021 Karlsson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Purpose Retinal oximetry is a technique based on spectrophotometry where images are analyzed with software capable of calculating vessel oxygen saturation and vessel diameter. In this study, the effect of automation of measurements of retinal vessel oxygen saturation and vessel diameter is explored. Methods Until now, operators have had to choose each vessel segment to be measured explicitly. A new, automatic version of the software automatically selects the vessels once the operator defines a measurement area. Five operators analyzed image pairs from the right eye of 23 healthy subjects with semiautomated retinal oximetry analysis software, Oxymap Analyzer (v2.5.1), and an automated version (v3.0). Inter- and intra-operator variability was investigated using the intraclass correlation coefficient (ICC) between oxygen saturation measurements of vessel segments in the same area of the retina. Results For semiautomated saturation measurements, the inter-rater ICC was 0.80 for arterioles and venules. For automated saturation measurements, the inter-rater ICC was 0.97 for arterioles and 0.96 for venules. For semiautomated diameter measurements, the inter-rater ICC was 0.71 for arterioles and venules. For automated diameter measurements the inter-rater ICC was 0.97 for arterioles and 0.95 for venules. The inter-rater ICCs were different (p < 0.01) between the semiautomated and automated version in all instances. Conclusion Automated measurements of retinal oximetry values are more repeatable compared to measurements where vessels are selected manually.Peer reviewe