Retinal oxygen saturation in monoclonal gammopathies patients: A pilot study.

PURPOSE: The aim of this pilot study was to assess oxygen saturation in retinal blood vessels in patients with monoclonal gammopathies (MGs). METHODS: Thirty-one patients with MGs (11 women and 20 men, mean age 65.9 ± 8.9 years) were enrolled during 2016-2020. The patients were diagnosed at the Haemato-Oncology Department and subsequently examined at the Ophthalmology Department before initiating systemic therapy. All patients were subjected to automatic retinal oximetry (Oxymap ehf.) and had their fundus photographed (Topcon TRC-50DX retinal camera). We assessed the association between retinal oxygen saturation (SatO2 ) - arterial SatO2 , venous SatO2 and arterio-venous (AV) difference-and MGs parameters: serum monoclonal immunoglobulin (M-protein) level and serum immunoglobulin-free light chains (FLC kappa and lambda), total protein, serum viscosity, haemoglobin, albumin, lactate dehydrogenase, C-reactive protein, creatinine and serum calcium level. Hyperviscosity-related retinopathy was also evaluated. RESULTS: Statistical analysis showed a significant positive correlation (r = 0.462; p = 0.009) between the AV difference and the haemoglobin level. A significant, medium strong negative correlation was found between the AV difference and the serum levels of the monoclonal light lambda chains (r = -0.450; p = 0.011). Contrary to expectations, no statistically significant correlation was found between retinal oxygen saturation and the total protein or viscosity. CONCLUSION: This study found correlation between retinal oxygen saturation and certain parameters in the blood of patients with MGs. Increasing levels of monoclonal immunoglobulin seem to reduce oxygen absorption in retinal arterioles, resulting in a lower AV difference, particularly in patients with a high free light chain level.

Hypertension, hyperlipidaemia and thrombophilia as the most common risk factors for retinal vein occlusion in patients under 50 years.

BACKGROUND AND AIMS: Cardiovascular (CV) diseases are the most common risk factors (RFs) for retinal vein occlusion (RVO) development in general. The aim of this study was to identify the most frequent causes of RVO in patients under 50. METHODS: We retrospectively evaluated a group of patients with RVO under 50 years. The parameters of interest included age and sex, RVO type, presence of arterial hypertension (HT), hyperlipidaemia (HLD), diabetes mellitus (DM), congenital thrombophilic disorder (TD), obstructive sleep apnoea syndrome (OSAS), thyroid eye disease (TED), use of hormone contraception (HC) or hormone replacement therapy (HRT), glaucoma and other potential RFs. Patients with central RVO (CRVO), hemi-central RVO (HRVO), branch RVO (BRVO), impending CRVO and combined arterial-venous (AV) occlusion were included. RESULTS: The group consisted of 110 eyes of 103 patients. CV disease was the most common systemic abnormality. 55.3% patients had HT, 17.5% had HLD. TD was the third most frequent RF (12.6%). The cohort also included patients with DM (6.8%), glaucoma (6.8%) and women using HC/HRT (26.2% of female patients). There were isolated cases of RVO due to retinal vasculitis, intense exercise, antiphospholipid syndrome and COVID-19 pneumonia. None of the patients had OSAS, TED or a haemato-oncological disease. The etiology remained unexplained in 20.4% patients. No difference was observed in RF occurrence between patients with CRVO and HRVO and those with BRVO. CONCLUSION: The most common systemic abnormality in our cohort was CV disease, especially HT and HLD. The risk factors for central, hemi-central and branch RVOs were similar.

Retinal oxygen saturation is associated with HbA1c but not with short-term diabetes control, internal environment, smoking and mild retinopathy - ROXINEGLYD study.

PURPOSE: Purpose of this prospective uncontrolled single-centre pilot study was to find an association of retinal oxygen saturation (SatO2 ) with acid-base balance (ABB), carboxyhaemoglobin concentration, current plasma glucose concentration (PG), mean PG and PG variability over the last 72 hr, haemoglobin A1c (HbA1c), and other conditions. METHODS: Forty-one adults (17 men) with type 1 (N = 14) or type 2 (N = 27) diabetes mellitus, age 48.6 ± 13.5 years, diabetes duration 9 (0.1-36) years, BMI 29.4 ± 6.3 kg/m2 , and HbA1c 52 ± 12.7 mmol/mol completed the study. The 4-day study comprised two visits (Day l, Day 4) including 72 hr of continuous glucose monitoring (CGM) by iPro® 2 Professional CGM (Medtronic, MiniMed, Inc., Northridge, CA, USA). Retinal oximeter Oxymap T1 (Oxymap ehf., Reykjavik, Iceland) was used to assess SatO2 . RESULTS: Wilcoxon signed-rank test showed no SatO2 difference between eyes and visits. Spearman's correlation analysis revealed a significant correlation between arterial SatO2 and PG variability in type 2 diabetes mellitus, a positive correlation of venous SatO2 with HbA1c and with finger pulse oximetry. However, no correlation of SatO2 with ABB, carboxyhaemoglobin, current PG, mean PG over the 72 hr, age, diabetes duration, BMI, lipoproteinaemia, body temperature, systolic and diastolic blood pressure, heart rate, central retinal thickness and retinal nerve fibre layer thickness was found. CONCLUSION: This study confirmed the association of venous SatO2 with long-term but not with short-term diabetes control, ABB and other conditions. The increased SatO2 and questionable impact of PG variability on retinal SatO2 is a research challenge.

Changes in oxygen saturation and the retinal nerve fibre layer in patients with optic neuritis associated with multiple sclerosis in a 6-month follow-up.

PURPOSE: Optic neuritis (ON) is an inflammatory demyelinating disorder of the optic nerve, which can be the first manifestation of multiple sclerosis (MS). The main goal was to assess changes in the retinal nerve fibre layer (RNFL) and in retinal oxygen saturation [arterial (AS), venous (VS) and arterio-venous (A-V) difference] in the affected and unaffected eye. METHODS: Fifty patients with ON due to MS within 3 months of onset of symptoms were enrolled (17 males, mean age 35.3). All patients were examined at baseline (V1) and after 6 months (V2) using optical coherence tomography (OCT) to get RNFL values; automatic retinal oximetry to obtain saturation values; and ultrasound to exclude arterial stenosis, and orbital colour Doppler imaging was performed in the ophthalmic artery. RESULTS: At V1, AS was significantly increased in affected eye compared to unaffected eye (99.5% versus 98.0%, p = 0.03). Significant decrease in A-V difference from baseline was detected in both eyes for ON eye: 32.0% versus 29.0%, p = 0.004; for fellow eye: 31.4% versus 30.0%, p = 0.04. We did not observe any changes in retinal vessel diameter. There were no changes observed in blood flow in ophthalmic artery. At V1, there were no significant differences in RNFL, and significant loss of RNFL was confirmed in the affected eye at V2 (95 µm versus 86 µm, p = 0.0002) and in comparison with the fellow eye (86 µm versus 94 µm, p = 0.0002). There were no correlations between RNFL and saturation values at V1, although at V2, there was a negative correlation between the RNFL and AS (Spearman's rho = -0.480, p = 0.003) and between the RNFL and VS (rho = -0.620, p = 0.00007). CONCLUSION: Retinal oximetry is altered in both eyes in MS patients with unilateral ON. During the course of the disease, the retinal oxygen consumption decreases to a different degree in each eye and this change is not completely followed by changes in the RNFL thickness, suggesting either sub-clinical ON or systemic effects in the clinically unaffected eye. Since this is the first and initial longitudinal evaluation of the saturation changes in MS patients, the clinical value of these findings needs to be deeper evaluated in the future studies.

Correlation Between Ischemic Index of Retinal Vein Occlusion and Oxygen Saturation in Retinal Vessels.

PURPOSE: To evaluate the relationship between the ischemic index and the oxygen saturation in retinal vessels in patients with retinal vein occlusion. DESIGN: Prospective, cross-sectional study. METHODS: We performed a prospective study. The cohort consisted of 43 eyes of 43 patients with retinal vein occlusions (RVO), 23 of whom had central retinal vein occlusions (CRVO) and 20 who had branch retinal vein occlusions (BRVO). We evaluated the retinal vessel saturation using an automatic retinal oximetry device. The retinal ischemic index (ISI) was determined using ultra-widefield fluorescein angiography. RESULTS: Mean arterial saturation (±SD) was 100% ± 11%, mean vein saturation was 52% ±13%, and mean A-V difference was 48% ± 16% in eyes with BRVO. The average ISI in the same group was 0.48 (range 0-1). There was no statistically significant correlation between the retinal ischemic index and retinal saturation in the BRVO group. The affected eye in the CRVO group had a mean arterial saturation of 101% ± 6%, vein saturation of 44% ± 11 % and A-V difference of 58% ± 10%. The average ISI in the CRVO group was 0.54 (range 0-1). A statistically significant negative correlation between ISI and vein saturation was found in the CRVO group (r = -0.686; P =.0003). A significant positive correlation between ISI and the A-V difference was found in the CRVO group (r = 0.893; P <.0001). CONCLUSIONS: Oxygen saturation in the retinal vein and the arteriovenous difference correlated with the ischemic index in CRVO patients. No correlation was found for BRVO patients.

Changes in oxygen saturation and the retinal nerve fibre layer in patients with optic neuritis - a pilot study.

PURPOSE: Assessment of retinal oxygen saturation, thickness of a retinal nerve fibre layer (RNFL) and functional changes in the optic nerve during optic neuritis (ON) in patients with multiple sclerosis (MS). METHODS: Thirty-two patients with ON due to MS within 3 months of onset of symptoms were enrolled [22 females, 10 males, age 34 ± 9 years, median 32.5 years, 22 patients with the clinically isolated syndrome (CIS), 10 patients with relapsing-remitting from of MS (RRMS)]. All patients were examined using optical coherence tomography (OCT model 4000, Carl Zeiss Meditec, Dublin, CA, USA), automatic optical oximetry (Oxymap ehf, Reykjavik, Iceland) and using visual evoked potentials (VEP) (Metronic Keypoint® , Minneapolis, MN, USA). RESULTS: Arterio-venous difference (AVD) was increased in patients ON affected eye compared to patients' unaffected eye (PUE) [34.2 ± 4.7 versus 31.3 ± 4.6, p = 0.044 (mean ± standard deviation)]. No statistically significant difference was found in vessel oxygen saturation as well as in RNFL thickness in ON affected eyes when compared to unaffected MS eyes and healthy individuals. Significantly lower optic nerve conduction velocity was found in the affected eye when compared to unaffected MS eye and healthy (p < 0.0001 for both comparisons). No correlation between oxygen saturation values and VEP was observed in patients with MS. CONCLUSION: The AVD in oxygen saturation is altered in patients with acute ON. In the early stage of ON, AVD could reflect inflammatory and metabolic changes in the affected eye. Therefore, oximetry could be used as another diagnostic method in MS patients in suspicion of ON. This result would be promising for future investigation in this field.

The effect of pars plana vitrectomy and nuclear cataract on oxygen saturation in retinal vessels, diabetic and non-diabetic patients compared.

PURPOSE: To determine the effect of pars plana vitrectomy (PPV) on oxygen saturation in retinal vessels in patients with diabetes and non-diabetes after a 1-year follow-up. METHODS: This was a prospective consecutive interventional case series in 82 eyes in 82 patients. The sample consisted of 25 patients with non-proliferative diabetic retinopathy with macular oedema based on vitreoretinal traction or epiretinal membrane (ERM) and 57 non-diabetic patients with macular hole and ERM. Automatic retinal oximetry (Oxymap Inc.) was used on all patients 24 hr prior to PPV, and it was also used 7 and 52 weeks after PPV (classic 20G or sutureless 23G). We analysed the data according to subgroup diagnosis and lens status. RESULTS: Arterial saturation increased significantly from 96.4 ± 2.9% at baseline to 96.6 ± 3.4% at week 7 and 97.3 ± 3.4% at week 52 (p < 0.0001; Friedman test). Vein saturation also increased significantly from 63.5 ± 7.9% at baseline to 66.1 ± 7.7% and 67.0 ± 7.2% at weeks 7 and 52 (p < 0.0001; Friedman test). The value of the arteriovenous (A-V) difference decreased significantly after vitrectomy from 32.8 ± 7.5% at baseline to 30.5 ± 7.5% and 30.3 ± 7.0% at weeks 7 and 52 (p < 0.0001; Friedman test). The subgroup analysis revealed that in patients with diabetes, there were no statistically significant changes in oxygen saturation in blood vessels or in the A-V difference after PPV. After vitrectomy, retinal vessel diameter reduced by about 3.5% in both groups of patients. Further, the analysis revealed that opacification of the lens leads to a decrease in oxygen saturation in contrast to a clear lens and pseudophakic IOLs. CONCLUSION: Oxygen saturation is higher in the retinal veins and arteries after PPV in patients with non-diabetes, and this lasts for at least 52 weeks. In contrast, in patients with diabetes, there is no increase in oxygen saturation in the retinal vessels after vitrectomy. After vitrectomy, retinal vessel diameter reduced in both groups of patients. Further, the nuclear cataract progression has substantial effect on oximetry results. Patients with nuclear cataract exhibited an increase in saturation in both arteries and veins, but the A-V difference remained the same.

The effect of pars plan vitrectomy on oxygen saturation in retinal vessels--a pilot study.

PURPOSE: To determine the effect of pars plana vitrectomy (PPV) on oxygen saturation in retinal vessels. METHODS: We performed a prospective consecutive interventional case series of 20 eyes of 20 patients with macular hole or epiretinal membrane. We performed automatic retinal oximetry (Oxymap Inc., Reykjavik, Iceland) in each patient 24 hr prior to and 45 days (range 42-49) after PPV (classic 20G or sutureless 23G). We analysed oxygen saturations in retinal arteries and veins. Vessel segments of first or second degree were selected. The same segment was analysed before and after PPV. Oximetry data were compared by paired two-tailed t-test. RESULTS: Pars plana vitrectomy did not alter arterial haemoglobin saturation with oxygen (98±2% prior to the surgery and 98±3% after the procedure, p=0.549). The mean venous haemoglobin saturation with oxygen increased after vitrectomy from 63±10% to 66±8% (p=0.012). CONCLUSIONS: Oxygen saturation is higher in retinal veins after pars plana vitrectomy. Further studies are needed to unveil the mechanism of how vitrectomy affects oxygen metabolism in the retina.