Retinal oxygen saturation changes progressively over time in diabetic retinopathy.

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 DownloadPurpose: According to cross-sectional studies, oxygen saturation is elevated in retinal vessels in diabetic patients. We evaluated how retinal oxygenation (metabolic marker), vessel diameters and retinopathy grade (structural markers) change over time in diabetic patients. Design: Prospective cohort study following screening in a hospital setting. Methods: Retinal oximetry images were acquired in 214 patients with the Oxymap T1 oximeter. Imaging was repeated after a median of 3.0 years (range 0.76-6.8 years). Oxygen saturation and vessel diameters were measured in the right eye. Semiquantitative grading of retinopathy according to international guidelines and red lesion count were performed on fundus photographs. Results: Retinopathy grade according to the international semiquantitative grading system was unchanged. Arteriolar saturation increased by 0.75±0.15 percentage points per year of follow-up (p0.44). Conclusions: Oxygen saturation in larger retinal vessels can increase and arteriovenous difference can decrease over time in diabetic patients without any observable changes in retinopathy grade. The results suggest that changes in retinal oxygen saturation may precede progression of diabetic retinopathy or that oxygen saturation is more sensitive to disease progression than retinopathy grade.Icelandic Center for Research Toyota Foundation University of Iceland Research Fund Helga Jonsdottir and Sigurlidi Kristjansson Memorial Fun

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

Retinal oxygen metabolism in patients with mild cognitive impairment

Publisher's version (útgefin grein)Introduction We have previously reported that retinal vessel oxygen saturation is increased in mild-to-moderate dementia of Alzheimer's type when compared with healthy individuals. Mild cognitive impairment (MCI) is the predementia stage of the disease. The main purpose was to investigate if these changes are seen in MCI. Methods Retinal vessel oxygen saturation was measured in 42 patients with MCI and 42 healthy individuals with a noninvasive retinal oximeter, Oxymap T1. The groups were paired according to age. Results Arteriolar and venular oxygen saturation was increased in MCI patients compared to healthy individuals (arterioles: 93.1 ± 3.7% vs. 91.1 ± 3.4%, P = .01; venules: 59.6 ± 6.1% vs. 54.9 ± 6.4%, P = .001). Arteriovenous difference was decreased in MCI compared to healthy individuals (33.5 ± 4.5% vs. 36.2 ± 5.2%, P = .01). Discussion Increased retinal vessel oxygen saturation and decreased arteriovenous difference in MCI could reflect less oxygen extraction by retinal tissue. This indicates that retinal oxygen metabolism may be affected in patients with MCI.Olof Birna Olafsdottir received a grant from the Icelandic Centre for Research. The sponsor did not have any role in the study design; in the collection, analysis, and interpretation of the data; in the writing of the report, and in the decision to submit the article for publication.Peer Reviewe

Retinal oxygen metabolism in patients with mild cognitive impairment

Publisher's version (útgefin grein)Introduction We have previously reported that retinal vessel oxygen saturation is increased in mild-to-moderate dementia of Alzheimer's type when compared with healthy individuals. Mild cognitive impairment (MCI) is the predementia stage of the disease. The main purpose was to investigate if these changes are seen in MCI. Methods Retinal vessel oxygen saturation was measured in 42 patients with MCI and 42 healthy individuals with a noninvasive retinal oximeter, Oxymap T1. The groups were paired according to age. Results Arteriolar and venular oxygen saturation was increased in MCI patients compared to healthy individuals (arterioles: 93.1 ± 3.7% vs. 91.1 ± 3.4%, P = .01; venules: 59.6 ± 6.1% vs. 54.9 ± 6.4%, P = .001). Arteriovenous difference was decreased in MCI compared to healthy individuals (33.5 ± 4.5% vs. 36.2 ± 5.2%, P = .01). Discussion Increased retinal vessel oxygen saturation and decreased arteriovenous difference in MCI could reflect less oxygen extraction by retinal tissue. This indicates that retinal oxygen metabolism may be affected in patients with MCI.Olof Birna Olafsdottir received a grant from the Icelandic Centre for Research. The sponsor did not have any role in the study design; in the collection, analysis, and interpretation of the data; in the writing of the report, and in the decision to submit the article for publication.Peer Reviewe

Oxygen saturation in branch retinal vein occlusion.

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.The aim of this study was to test whether oxygen saturation in retinal blood vessels is affected by branch retinal vein occlusion (BRVO). The spectrophotometric retinal oximeter is based on a fundus camera. It simultaneously captures images of the retina at 586 and 605 nm and calculates optical density (absorbance) of retinal vessels at both wavelengths. The ratio of the two optical densities is approximately linearly related to haemoglobin oxygen saturation. Relative oxygen saturation was measured in retinal blood vessels in 24 patients with BRVO. Friedman's test and Dunn's post test were used for statistical analyses. Results:  Oxygen saturation in occluded venules ranged from 12% to 93%. The median oxygen saturation was 59% (range 12-93%, n = 22) in affected retinal venules, 63% (23-80%) in unaffected venules in the BRVO eye and 55% (39-80%) in venules in the fellow eye (p = 0.66). Corresponding values for arterioles were 101% (89-115%, n = 18), 95% (85-104%) (p < 0.05) and 98% (84-109%). Venular saturation in BRVO is highly variable between patients. Hypoxia is seen in some eyes but not in others. This may reflect variable severity of disease, degree of occlusion, recanalization, collateral circulation, tissue atrophy, arteriovenous diffusion or vitreal transport of oxygen.Icelandic Center for Research (Ranni's) Eimskip University Fund University of Iceland Research Fund Landspitali-University Hospital Research Fund Helga Jonsdottir and Sigurlidi Kristjansson Memorial Fun

Retinal oxygen saturation is altered in diabetic retinopathy.

To access publisher full text version of this article. Please click on the hyperlink in Additional Links field.AIM: Retinal oxygen metabolism is thought to be affected in diabetic retinopathy. The aim of this study was to test whether retinal vessel oxygen saturation is different in patients with diabetic retinopathy from that in healthy controls. METHODS: The retinal oximeter is based on a fundus camera. It estimates retinal vessel oxygen saturation from light absorbance at 586 nm and 605 nm. Retinal vessel oxygen saturation was measured in one major temporal retinal arteriole and venule in healthy volunteers and in patients with diabetic retinopathy. RESULTS: Oxygen saturation in the retinal arterioles of healthy volunteers was 93 ± 4% and 58 ± 6% in venules (mean ± SD, n=31). The corresponding values for all diabetic patients (n=20) were 101 ± 5% and 68 ± 7%. The difference between healthy volunteers and diabetic patients was statistically significant (p < 0.001 for arterioles and venules). Three subgroups of diabetic patients (background retinopathy, macular oedema and pre-proliferative/proliferative retinopathy) all had higher saturation values than the healthy volunteers (p < 0.05 for arterioles and venules). CONCLUSION: Retinal vessel oxygen saturation is higher in patients with diabetic retinopathy than in healthy controls. Possible explanations include shunting of blood through preferential channels, bypassing non-perfused capillaries in the capillary network. Parts of the retinal tissue may be hypoxic while blood in larger vessels has high oxygen saturationIcelandic Centre for Research (Rannis), Eimskip University, Univ. of Iceland, Landspitali-University Hospital

Oxygen saturation in central retinal vein occlusion

To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldPURPOSE: To test whether oxygen saturation is affected in retinal blood vessels in patients with central retinal vein occlusion (CRVO). DESIGN: Prospective observational case series. METHODS: Oxygen saturation of hemoglobin was measured in retinal blood vessels in 10 patients with unilateral CRVO. The duration of CRVO before measurement was from 1 day to about 6 months. Two patients were excluded because of poor quality of oximetry images. The spectrophotometric retinal oximeter is based on a fundus camera. It simultaneously captures images of the retina at 605 nm and 586 nm and calculates optical density (absorbance) of retinal vessels at both wavelengths. The ratio of the 2 optical densities is approximately linearly related to hemoglobin oxygen saturation. Mean oxygen saturation was calculated for first- and second-degree arterioles and venules in both eyes of each patient. RESULTS: The mean oxygen saturation of hemoglobin in retinal venules was 49% ± 12% (mean ± SD, n = 8) in eyes affected by CRVO and 65% ± 6% in unaffected fellow eyes (P = .003). The mean arteriolar oxygen saturation was 99% ± 3% in CRVO eyes and 99% ± 6% in the fellow eyes. Venular oxygen saturation was variable within and between CRVO eyes. CONCLUSIONS: Oxygen saturation in retinal venules is lower in eyes with CRVO than in fellow eyes and there is considerable variability within and between CRVO eyes. Arteriolar saturation is the same in CRVO and fellow eyes. Retinal oxygenation is disturbed in CRVO

Retinal oxygen metabolism in exudative age-related macular degeneration.

To access publisher's full text version of this article click on the hyperlink at the bottom of the pageTo determine whether retinal vessel oxygen saturation in patients with exudative age-related macular degeneration (AMD) is different from that of a healthy population.Oxygen saturation was measured in retinal arterioles and venules in 46 eyes of 46 treatment-naïve exudative AMD patients and 120 eyes of 120 healthy controls. Simple and multiple linear regression analyses were used to compare the two study groups.Oxygen saturation in retinal venules increases with age in patients with exudative AMD (0.45 ± 0.19% per year; p = 0.026), while it decreases with age in healthy individuals (-0.13 ± 0.03% per year; p = 0.0002). The slopes are statistically different (ANCOVA; p = 0.0003). The reverse is true for the arteriovenous difference in oxygen saturation, which decreases with age in AMD patients (-0.29 ± 0.16% per year; p = 0.065) and increases in healthy individuals (0.12 ± 0.03% per year; p < 0.0001). At age 80 years, AMD patients have 2.7 percentage points higher venous oxygen saturation than healthy persons and 4.2 percentage points less arteriovenous difference.The data suggest that retinal oxygen metabolism may be altered in exudative AMD. The arteriovenous difference is smaller in exudative AMD than in a healthy cohort, consistent with reduced oxygen extraction by retinal vessels in AMD patients. Further studies are needed to fully understand the role of retinal oxygen metabolism in the pathophysiology of exudative AMD.Prevention of Blindness Fund Landspitali-University Hospital Research Fund Rasmussen Foundation University of Iceland Research Fund Icelandic Centre for Research (Rannis

Retinal oximetry is affected in multiple sclerosis.

To access publisher's full text version of this article click on the hyperlink belowStructural and physiological abnormalities have been reported in the retina in patients with multiple sclerosis (MS). Retinal oximetry has recently detected changes in retinal oxygen metabolism in Alzheimer's disease and mild cognitive impairment. Our goal was to determine whether oxygen saturation in retinal blood vessels of patients with patients is different from that of a healthy population. Oxygen saturation of haemoglobin was measured in retinal blood vessels, using imaging with spectrophotometric noninvasive retinal oximeter. Eight MS patients with history of optic neuritis were measured and compared to 22 healthy individuals matched in age and gender. Venular oxygen saturation was increased in patients with MS compared to healthy individuals (70.7 ± 3.4% versus 66.2 ± 4.7; p = 0.021, mean ± SD). The arteriovenous (AV) difference was lower in patients with MS compared to healthy (26.6 ± 3.6% versus 30.5 ± 4.8%; p = 0.049). There was no difference measured in arterioles when patients with MS (97.3 ± 1.7%) and healthy individuals (96.7 ± 2.8%) were compared. Increased venular oxygen saturation and lower AV difference in patients with MS may indicate reduced oxygen uptake. This may be due to less oxygen demand following atrophy and may be a useful objective biomarker for MS. Further studies are needed to confirm and expand these findings.Association for Research in Vision and Ophthalmolog