Impaired retinal oxygen metabolism and perfusion are accompanied by plasma protein and lipid alterations in recovered COVID-19 patients.

The aim of the present study was to investigate retinal microcirculatory and functional metabolic changes in patients after they had recovered from a moderate to severe acute COVID-19 infection. Retinal perfusion was quantified using laser speckle flowgraphy. Oxygen saturation and retinal calibers were assessed with a dynamic vessel analyzer. Arterio-venous ratio (AVR) was calculated based on retinal vessel diameter data. Blood plasma samples underwent mass spectrometry-based multi-omics profiling, including proteomics, metabolomics and eicosadomics. A total of 40 subjects were included in the present study, of which 29 had recovered from moderate to severe COVID-19 within 2 to 23 weeks before inclusion and 11 had never had COVID-19, as confirmed by antibody testing. Perfusion in retinal vessels was significantly lower in patients (60.6 ± 16.0 a.u.) than in control subjects (76.2 ± 12.1 a.u., p = 0.006). Arterio-venous (AV) difference in oxygen saturation and AVR was significantly lower in patients compared to healthy controls (p = 0.021 for AVR and p = 0.023 for AV difference in oxygen saturation). Molecular profiles demonstrated down-regulation of cell adhesion molecules, NOTCH3 and fatty acids, and suggested a bisphasic dysregulation of nitric oxide synthesis after COVID-19 infection. The results of this study imply that retinal perfusion and oxygen metabolism is still significantly altered in patients well beyond the acute phase of COVID-19. This is also reflected in the molecular profiling analysis of blood plasma, indicating a down-regulation of nitric oxide-related endothelial and immunological cell functions.Trial Registration: ClinicalTrials.gov ( https://clinicaltrials.gov ) NCT05650905.

Safety and Tolerability of KIO-101 Eye Drops in Healthy Volunteers and Patients with Ocular Surface Disease-A Phase I Study.

PURPOSE: Inhibitors of dihydroorotate dehydrogenase (DHODH) have been found to be potent anti-inflammatory agents. Recently, a topical formulation (KIO-101 eye drops) of a DHODH inhibitor has been developed. The aim of the present study was to evaluate the safety and tolerability of KIO-101 eye drops in Healthy Volunteers (HVs) and patients with conjunctival hyperemia. METHODS: The study was carried out in a double-masked, placebo-controlled, randomized, parallel-group design with two parts. In part I, HVs received single and multiple instillations (four times daily for 12 consecutive days) of KIO-101 eye drops in ascending doses of 0.05%, 0.15%, and 0.30%, respectively. Part II was conducted in patients with conjunctival hyperemia who received 0.15% KIO-101 eye drops twice daily for 12 consecutive days. Ophthalmic and systemic safety examinations were performed on all participants. In part II, ocular hyperemia grading and an ocular surface disease index (OSDI) questionnaire were performed. RESULTS: 24 HVs participated in part I and 21 patients in part II. KIO-101 eye drops were well tolerated in all subjects. No serious adverse events (SAEs) occurred, and all AEs that were reported were transient and considered mild to moderate. In the highest dose cohort (0.30%), epistaxis occurred in two subjects after multiple instillations. In part II, after 12 days treatment with 0.15% KIO-101, conjunctival hyperemia decreased by -1.1 ± 0.27 points in the treatment and -0.6 ± 0.79 points in the placebo group (p = 0.0385). OSDI decreased from 47.9 ± 18.7 to 27.6 ± 19.13 points in the treatment group, while in the placebo group, a change from 41.3 ± 12.08 to 27.3 ± 18.63 points occurred. CONCLUSIONS: A 12-day treatment regimen with topical KIO-101 eye drops at low and mid doses was safe and well tolerated in both HVs and patients with conjunctival hyperemia. The obtained results point towards an early sign of reduction in conjunctival hyperemia.

Plasma Instead of Serum Avoids Critical Confounding of Clinical Metabolomics Studies by Platelets.

Metabolomics is an emerging and powerful bioanalytical method supporting clinical investigations. Serum and plasma are commonly used without rational prioritization. Serum is collected after blood coagulation, a complex biochemical process involving active platelet metabolism. This may affect the metabolome and increase the variance, as platelet counts and function may vary substantially in individuals. A multiomics approach systematically investigating the suitability of serum and plasma for clinical studies demonstrated that metabolites correlated well (n = 461, R2 = 0.991), whereas lipid mediators (n = 83, R2 = 0.906) and proteins (n = 322, R2 = 0.860) differed substantially between specimen. Independently, analysis of platelet releasates identified most biomolecules significantly enriched in serum compared to plasma. A prospective, randomized, controlled parallel group metabolomics trial with acetylsalicylic acid administered for 7 days demonstrated that the apparent drug effects significantly differ depending on the analyzed specimen. Only serum analyses of healthy individuals suggested a significant downregulation of TXB2 and 12-HETE, which were specifically formed during coagulation in vitro. Plasma analyses reliably identified acetylsalicylic acid effects on metabolites and lipids occurring in vivo such as an increase in serotonin, 15-deoxy-PGJ2 and sphingosine-1-phosphate and a decrease in polyunsaturated fatty acids. The present data suggest that plasma should be preferred above serum for clinical metabolomics studies as the serum metabolome may be substantially confounded by platelets.

The Impact of Photopigment Bleaching on the Human Rod Photoreceptor Subretinal Space Measured Via Optical Coherence Tomography.

Purpose: The purpose of this study was to investigate rod photopigment bleaching-driven intrinsic optical signals (IOS) in the human outer retina and its measurement repeatability based on a commercial optical coherence tomography (OCT) platform. Methods: The optical path length of the rod photoreceptor subretinal space (SRS), that is, the distance between signal bands of rod outer segment tips and retinal pigment epithelium, was measured in 15 healthy subjects in ambient light and during a long-duration bleaching white-light exposure. Results: On 2 identical study days (day 1 and day 2 [D1 and D2]), light stimulation resulted in a significant decrease in rod SRS by 21.3 ± 7.6% and 19.8 ± 8.5% (both P < 0.001), respectively. The test-retest reliability of the SRS maximum change of an individual subject was moderate for single measures (intraclass correlation coefficient [ICC] = 0.730, 95% confidence interval [CI] = 0.376, 0.900, P < 0.001) and good for average measures (ICC = 0.844, 95% CI = 0.546, 0.947, P < 0.001). The mean area under the stimulus response curve with values of 14.8 ± 9.4 and 15.5 ± 7.5 µm × minutes (P = 0.782) showed excellent agreement between the stimulus response on D1 and D2. Intermittent dark adaptation of the retina led to an initial increase of the SRS by 6.1% (P = 0.018) and thereafter showed a decrease toward baseline, despite continued dark adaptation. Conclusions: The data indicate the potential of commercial OCT in measuring slow IOS in the outer retina suggesting that the rod SRS could serve as a biomarker for photoreceptor function. The presented approach could provide an easily implementable clinical tool for the early detection of diseases affecting photoreceptor health.

Repeatability of biometry in patients with meibomian gland dysfunction before and after vectored thermal pulsation therapy: A randomized, controlled trial.

PURPOSE: To evaluate the effect of vectored thermal pulsation therapy (VTPT) on the repeatability of biometry readings of two different optical biometers in patients with meibomian gland dysfunction (MGD). METHODS: Patients affected by MGD were included in this prospective, randomized, controlled, investigator-masked study. One eye was randomized to VTPT (LipiFlow®, Johnson & Johnson), and the contralateral eye served as a control. Three visits were scheduled at baseline, 2 weeks and 3 months after the treatment. The main outcome parameter of the study was the repeatability of three calculations of emmetropic intraocular lens power (EIOLP) at the 3 months visit as compared to baseline using an optical biometer (IOLMaster® 700, Carl Zeiss Meditec AG). Repeatability of different keratometry values obtained by the optical biometer and a Placido-disc topographer (MS-39®, CSO) served as secondary outcome parameters. RESULTS: Twenty-nine patients were included in the final analysis. While tear film parameters improved in the study eyes, there were no significant differences regarding the repeatability of three EIOLP measurements between baseline and 3-months-visit in both eyes (p > 0.05) and keratometry measurements in both the optical biometer and the Placido-disc topographer. Remarkably, throughout all study visits, there were some outliers regarding the repeatability of measurements. CONCLUSION: While both devices showed high repeatability regarding EIOLP and keratometry, future studies are needed to detect high-risk patients for poor repeatability.

An Exploratory Retrospective Data Analysis Comparing the Outcomes of Selective Laser Trabeculoplasty and Argon Laser Trabeculoplasty in Patients with Open-Angle Glaucoma or Ocular Hypertension in Vienna, Austria, from the Year 2012 to 2022.

Background and Objectives: The aim of the present study was to compare the short-term outcomes of selective laser trabeculoplasty (SLT) with argon laser trabeculoplasty (ALT) in patients with glaucoma in a real-world setting. Materials and Methods: The present study was conducted as a retrospective case-control study. The main outcome was the change in intraocular pressure (IOP) three months after laser surgery. In addition, the number of substances used for lowering of IOP and adverse events (AEs) were assessed. Results: Charts from 25 patients were included in the present study, of which 12 had received ALT and 13 SLT. In both groups, IOP significantly decreased from baseline values 6 weeks and 3 months after laser treatment (p < 0.01 vs. baseline at each timepoint for both groups). While after 6 weeks, no difference between groups was found, after 3 months, the decrease in IOP was significantly more pronounced in the SLT group (-26 ± 21% in the ALT group vs. -41 ± 14% in the SLT group, p = 0.018 between groups, ANOVA). Three months after laser treatment, the number of IOP-lowering substances used by each patient had decreased with no difference between groups (ALT: from 2.7 ± 0.8 to 2.3 ± 0.9 substances; SLT: from 1.8 ± 1.2 to 1.3 ± 1.1 substances, p = 0.386). Only a few AEs were observed. Two patients in the ALT and one patient in the SLT group required trabeculectomy within 1 year after laser treatment due to IOP decompensation. Conclusions: In the present study, SLT was at least as effective as ALT with fewer AEs and a similar reduction in concomitant IOP-lowering medication.

Therapeutic Potential of Cannabinoids in Glaucoma.

Glaucoma is a leading cause of irreversible blindness worldwide. To date, intraocular pressure (IOP) is the only modifiable risk factor in glaucoma treatment, but even in treated patients, the disease can progress. Cannabinoids, which have been known to lower IOP since the 1970s, have been shown to have beneficial effects in glaucoma patients beyond their IOP-lowering properties. In addition to the classical cannabinoid receptors CB1 and CB2, knowledge of non-classical cannabinoid receptors and the endocannabinoid system has increased in recent years. In particular, the CB2 receptor has been shown to mediate anti-inflammatory, anti-apoptotic, and neuroprotective properties, which may represent a promising therapeutic target for neuroprotection in glaucoma patients. Due to their vasodilatory effects, cannabinoids improve blood flow to the optic nerve head, which may suggest a vasoprotective potential and counteract the altered blood flow observed in glaucoma patients. The aim of this review was to assess the available evidence on the effects and therapeutic potential of cannabinoids in glaucoma patients. The pharmacological mechanisms underlying the effects of cannabinoids on IOP, neuroprotection, and ocular hemodynamics have been discussed.

Effect of Treatment with Topical Azithromycin or Oral Doxycycline on Tear Film Thickness in Patients with Meibomian Gland Dysfunction: A Randomized Controlled Trial.

Purpose: This prospective, randomized, observer-masked, parallel-group study aimed to compare the effect of topical azithromycin and oral doxycycline on tear film thickness (TFT) and signs and symptoms of ocular surface disease (OSD) in patients with meibomian gland dysfunction (MGD). Methods: Patients were randomized to either receive topical azithromycin or oral doxycycline. After a baseline visit, three follow-up visits at intervals of 2 weeks were scheduled. Main outcome of the study was change in TFT as measured with ultrahigh resolution optical coherence tomography. Results: Twenty patients were included in the analysis. TFT significantly increased in both groups (P = 0.028 vs. baseline) with no difference between the groups (P = 0.096). As secondary outcomes, ocular surface disease index (OSDI) score and composite signs of OSD significantly decreased in both groups (P = 0.023 for OSDI and P = 0.016 for OSD signs vs. baseline). While eye-related adverse events (AEs) occurred more frequently in the azithromycin group, systemic AEs were more common in the doxycycline group. Conclusions: Both treatments improved signs and symptoms of OSD in patients with MGD with no difference between the groups. Due to the higher frequency of systemic side effects of doxycycline, azithromycin eye drops seem to be an alternative with comparable efficacy. Clinical Trial Registration number: NCT03162497.

Effect of Antibiotic Eye Drops on the Nasal Microbiome in Healthy Subjects-A Pilot Study.

BACKGROUND: Antibiotic eye drops are frequently used in clinical practice. Due to the anatomical connection via the nasolacrimal duct, it seems possible that they have an influence on the nasal/pharyngeal microbiome. This was investigated by using two different commonly used antibiotic eye drops. METHODS: 20 subjects were randomized to four groups of five subjects receiving eye drops containing gentamicin, ciprofloxacin, or, as controls, unpreserved povidone or benzalkonium chloride-preserved povidone. Nasal and pharyngeal swabs were performed before and after the instillation period. Swabs were analyzed by Illumina next-generation sequencing (NGS)-based 16S rRNA analysis. Bacterial culture was performed on solid media, and bacterial isolates were identified to the species level by MALDI-TOF MS. Species-dependent antimicrobial susceptibility testing was performed using single isolates and pools of isolates. RESULTS: Bacterial richness in the nose increased numerically from 163 ± 30 to 243 ± 100 OTUs (gentamicin) and from 114 ± 17 to 144 ± 45 OTUs (ciprofloxacin). Phylogenetic diversity index (pd) of different bacterial strains in the nasal microbiome increased from 12.4 ± 1.0 to 16.9 ± 5.6 pd (gentamicin) and from 10.2 ± 1.4 to 11.8 ± 3.1 pd (ciprofloxacin). Unpreserved povidone eye drops resulted in minimal changes in bacterial counts. Preservative-containing povidone eye drops resulted in no change. A minor increase (1-2-fold) in the minimal inhibitory concentration (MIC) was observed in single streptococcal isolates. CONCLUSIONS: Antibiotic eye drops could affect the nasal microbiome. After an instillation period of seven days, an increase in the diversity and richness of bacterial strains in the nasal microbiome was observed.

Classification of Tear Film Lipid Layer En Face Maps Obtained Using Optical Coherence Tomography and Their Correlation With Clinical Parameters.

PURPOSE: The purpose of this study was to investigate the correlation between the pattern of optical coherence tomography (OCT) en face maps of the tear film lipid layer (TFLL) and lipid layer thickness (LLT), fluorescein breakup time (FBUT), and Schirmer I test values in healthy subjects. METHODS: Measurements from four clinical data sets were retrospectively analyzed, and TFLL patterns were classified into 3 categories: homogeneous (HOM), wavy (WAV), or dotted (DOT) appearance. Linear mixed model analyses were performed. Intraclass correlation coefficients and index of qualitative variation were computed to investigate interrater and intrasubject variabilities. RESULTS: For the LLT, a significant difference between HOM and DOT ( P < 0.001, ß HOMvsDOT = -6.42 nm) and WAV and DOT ( P = 0.002, ß WAVvsDOT = -4.04 nm) was found. Furthermore, the difference between WAV and DOT regarding FBUT ( P < 0.001, ß WAVvsDOT = -3.065 seconds) was significant, while no significant differences between any of the classes with respect to the Schirmer I test values were found. An intraclass correlation coefficient of 89.0% reveals a good interrater reliability, and an index of qualitative variation of 60.0% shows, on average, a considerable variability in TFLL pattern class for repeated measurements over 1 hour. CONCLUSIONS: A new classification method for OCT en face maps of the TFLL is presented. Significant differences between patterns were found with respect to LLT and FBUT. A dotted pattern on dark background appears to be the most stable type of TFLL. The analysis of OCT en face maps of the TFLL provides complimentary information to conventional imaging methods and might give new insights into the characteristics of the TFLL.

A multi-omics based anti-inflammatory immune signature characterizes long COVID-19 syndrome.

To investigate long COVID-19 syndrome (LCS) pathophysiology, we performed an exploratory study with blood plasma derived from three groups: 1) healthy vaccinated individuals without SARS-CoV-2 exposure; 2) asymptomatic recovered patients at least three months after SARS-CoV-2 infection and; 3) symptomatic patients at least 3 months after SARS-CoV-2 infection with chronic fatigue syndrome or similar symptoms, here designated as patients with long COVID-19 syndrome (LCS). Multiplex cytokine profiling indicated slightly elevated pro-inflammatory cytokine levels in recovered individuals in contrast to patients with LCS. Plasma proteomics demonstrated low levels of acute phase proteins and macrophage-derived secreted proteins in LCS. High levels of anti-inflammatory oxylipins including omega-3 fatty acids in LCS were detected by eicosadomics, whereas targeted metabolic profiling indicated high levels of anti-inflammatory osmolytes taurine and hypaphorine, but low amino acid and triglyceride levels and deregulated acylcarnitines. A model considering alternatively polarized macrophages as a major contributor to these molecular alterations is presented.

Neuro-vascular coupling and heart rate variability in patients with type II diabetes at different stages of diabetic retinopathy.

Aims/Hypothesis: There is evidence that diabetes is accompanied by a break-down of functional hyperemia, an intrinsic mechanism of neural tissues to adapt blood flow to changing metabolic demands. However, to what extent functional hyperemia is altered in different stages of diabetic retinopathy (DR) in patients with type II diabetes is largely unknown. The current study set out to investigate flicker-induced retinal blood flow changes in patients with type II diabetes at different stages of DR. Materials and methods: A total of 76 subjects were included in the present parallel-group study, of which 56 had diabetes with either no DR or different stages of non-proliferative DR (n = 29 no DR, 12 mild DR, 15 moderate to severe DR). In addition, 20 healthy subjects were included as controls. Retinal blood flow was assessed before and during visual stimulation using a combined measurement of retinal vessel calibers and blood velocity by the means of Doppler optical coherence tomography (OCT). To measure systemic autonomic nervous system function, heart rate variability (HRV) was assessed using a short-term orthostatic challenge test. Results: In healthy controls, retinal blood flow increased by 40.4 ± 27.2% during flicker stimulation. Flicker responses in patients with DR were significantly decreased depending on the stage of the disease (no DR 37.7 ± 26.0%, mild DR 26.2 ± 28.2%, moderate to severe DR 22.3 ± 13.9%; p = 0.035, ANOVA). When assessing systemic autonomous neural function using HRV, normalized low frequency (LF) spectral power showed a significantly different response to the orthostatic maneuver in diabetic patients compared to healthy controls (p < 0.001). Conclusion/Interpretation: Our study indicates that flicker induced hyperemia is reduced in patients with DR compared to healthy subjects. Further, this impairment is more pronounced with increasing severity of DR. Further studies are needed to elucidate mechanisms behind the reduced hyperemic response in patients with type II diabetes. Clinical trial registration: [https://clinicaltrials.gov/], identifier [NCT03 552562].

Retinal Oxygen Extraction in Patients with Primary Open-Angle Glaucoma.

Objective: To compare total retinal oxygen extraction between patients with primary open-angle glaucoma (POAG) and healthy control subjects. Design: A prospective, single-center, cross-sectional, case−control study performed at the Medical University of Vienna. Subjects: Forty patients with POAG and 40 age- and sex-matched control subjects. Methods: Total retinal blood flow was measured using Doppler optical coherence tomography (OCT). Retinal arterial and venous oxygen saturation was measured using reflectance spectroscopy. From these parameters, oxygen content in the retinal arterial and venous circulation as well as total retinal oxygen extraction were calculated. Results: Total retinal blood flow was lower in POAG (25.2 ± 6.7 µL/min) as compared to healthy control subjects (35.6 ± 8.3 µL/min, p < 0.001). Retinal arterial oxygen content was not different between the two groups (0.18 ± 0.01 mL(O2)/mL in both groups, p < 0.761), but retinal venous oxygen content was higher in POAG (0.15 ± 0.01 mL(O2)/mL) than in healthy controls (0.14 ± 0.01 mL(O2)/mL p < 0.001). Accordingly, retinal oxygen extraction was reduced in POAG (0.8 ± 0.3 µL(O2)/min as compared to healthy controls: 1.4 ± 0.4 µL(O2)/min, p < 0.001). There was a significant association between total retinal blood flow and total retinal oxygen extraction with measures of structural and functional damage (p < 0.001 each). Conclusions: This study indicates that POAG is associated with a reduction in total retinal oxygen extraction linked to structural and functional damage of the disease. Since the technology is non-invasive, it allows for longitudinal studies investigating to which degree low retinal oxygen extraction is linked to the progression of the disease.

Retinal Oxygen Metabolism in Patients With Type 2 Diabetes and Different Stages of Diabetic Retinopathy.

The aim of this cross-sectional study was to assess retinal oxygen metabolism in patients with type 2 diabetes and different stages of nonproliferative diabetic retinopathy (DR) (n = 67) compared with healthy control subjects (n = 20). Thirty-four patients had no DR, 15 had mild DR, and 18 had moderate to severe DR. Retinal oxygen saturation in arteries and veins was measured using the oxygen module of a retinal vessel analyzer. Total retinal blood flow (TRBF) was measured using a custom-built Doppler optical coherence tomography system. Retinal oxygen extraction was calculated from retinal oxygen saturation and TRBF. Arteriovenous difference in oxygen saturation was highest in healthy subjects (34.9 ± 7.5%), followed by patients with no DR (32.5 ± 6.3%) and moderate to severe DR (30.3 ± 6.5%). The lowest values were found in patients with mild DR (27.3 ± 8.0%, P = 0.010 vs. healthy subjects). TRBF tended to be higher in patients with no DR (40.1 ± 9.2 µL/min) and mild DR (41.8 ± 15.0 µL/min) than in healthy subjects (37.2 ± 5.7 µL/min) and patients with moderate to severe DR (34.6 ± 10.4 µL/min). Retinal oxygen extraction was the highest in healthy subjects (2.24 ± 0.57 µL O2/min), followed by patients with no DR (2.14 ± 0.6 µL O2/min), mild DR (1.90 ± 0.77 µL O2/min), and moderate to severe DR (1.78 ± 0.57 µL O2/min, P = 0.040 vs. healthy subjects). These results indicate that retinal oxygen metabolism is altered in patients with type 2 diabetes. Furthermore, retinal oxygen extraction decreases with increasing severity of DR.

Retinal oxygen saturation, vessel diameter and flicker response in eyes with specific subtypes of neovascular age-related macular degeneration during aflibercept treatment.

PURPOSE: To evaluate the effect of intravitreal aflibercept monotherapy on arterial and venous oxygen saturation, retinal vessel diameter and flicker response in patients with newly diagnosed specific subtypes of exudative maculopathy. METHODS: This prospective study included forty-four eyes of 44 patients with treatment-naïve polypoidal choroidal vasculopathy (PCV, n = 12), hemorrhagic choroidal neovascularization (hCNV, n = 12), pigment epithelium detachment (PED, n = 9) and type 3 MNV (RAP, n = 11). All patients received three initial aflibercept 2mg/0.05ml injections (Eylea®) in monthly intervals (loading phase) and were subsequently treated until month 12. Measurements of arterial and venous oxygen saturation, vessel diameters and flicker response were performed using the Dynamic Vessel Analyzer (DVA; IMEDOS, Jena, Germany). Statistical analysis was performed on the total population at baseline, after loading dose and at the last follow-up visit. RESULTS: The arterial oxygen saturation was 94.01±2.14% and showed no change after loading dose (93.94±2.88%, p = 0.4; estimated difference [confidence interval] -0.38 [-1.24; 0.48]) and at the last visit (95.48±1.90%; p = 0.1; -1.29 [-0.34; 2.91]). The venous oxygenation during treatment was 78.49±6.93% at baseline, 80.94±7.71% after 3-monthly injections (p = 0.7; -0.43 [-2.72; 1.86]) and 80.56±7.33% at month 12 (p = 0.5; 1.07 [-2.10; 4.24). The arterial and venous vessel diameters were 94±22µm and 131±19µm at baseline, and remained unchanged following aflibercept loading dose and at the last follow-up visit (p-value: p = 0.5; 2.30 [-5.00; 9.59] p = 0.8; 0.59 [-3.17; 4.34]). During stimulation with flicker light, arterial diameter changed by +1.24±4.93% at baseline and remained stable at month 3 (+2.70±5.95%; p = 0.5; 1.43 [-2.54; 5.41]) while the change in venous diameter during flicker stimulation was +4.52±4.45% at baseline and +4.13±3.65% after loading dose (p = 0.4, 5.18 [1.73; 8.63]). CONCLUSION: During intravitreal aflibercept treatment oxygen saturation, vessel diameter and flicker response did not change in the total population of patients with specific subtypes of exudative maculopathy.

Metabolic phenotyping of tear fluid as a prognostic tool for personalised medicine exemplified by T2DM patients.

Background/aims: Concerning healthcare approaches, a paradigm change from reactive medicine to predictive approaches, targeted prevention, and personalisation of medical services is highly desirable. This raises demand for biomarker signatures that support the prediction and diagnosis of diseases, as well as monitoring strategies regarding therapeutic efficacy and supporting individualised treatments. New methodological developments should preferably rely on non-invasively sampled biofluids like sweat and tears in order to provide optimal compliance, reduce costs, and ensure availability of the biomaterial. Here, we have thus investigated the metabolic composition of human tears in comparison to finger sweat in order to find biofluid-specific marker molecules derived from distinct secretory glands. The comprehensive investigation of numerous biofluids may lead to the identification of novel biomarker signatures. Moreover, tear fluid analysis may not only provide insight into eye pathologies but may also be relevant for the prediction and monitoring of disease progression and/ or treatment of systemic disorders such as type 2 diabetes mellitus. Methods: Sweat and tear fluid were sampled from 20 healthy volunteers using filter paper and commercially available Schirmer strips, respectively. Finger sweat analysis has already been successfully established in our laboratory. In this study, we set up and evaluated methods for tear fluid extraction and analysis using high-resolution mass spectrometry hyphenated with liquid chromatography, using optimised gradients each for metabolites and eicosanoids. Sweat and tears were systematically compared using statistical analysis. As second approach, we performed a clinical pilot study with 8 diabetic patients and compared them to 19 healthy subjects. Results: Tear fluid was found to be a rich source for metabolic phenotyping. Remarkably, several molecules previously identified by us in sweat were found significantly enriched in tear fluid, including creatine or taurine. Furthermore, other metabolites such as kahweol and various eicosanoids were exclusively detectable in tears, demonstrating the orthogonal power for biofluid analysis in order to gain information on individual health states. The clinical pilot study revealed that many endogenous metabolites that have previously been linked to type 2 diabetes such as carnitine, tyrosine, uric acid, and valine were indeed found significantly up-regulated in tears of diabetic patients. Nicotinic acid and taurine were elevated in the diabetic cohort as well and may represent new biomarkers for diabetes specifically identified in tear fluid. Additionally, systemic medications, like metformin, bisoprolol, and gabapentin, were readily detectable in tears of patients. Conclusions: The high number of identified marker molecules found in tear fluid apparently supports disease development prediction, developing preventive approaches as well as tailoring individual patients' treatments and monitoring treatment efficacy. Tear fluid analysis may also support pharmacokinetic studies and patient compliance control. Supplementary Information: The online version contains supplementary material available at 10.1007/s13167-022-00272-7.

Combining vascular and nerve fiber layer thickness measurements to model glaucomatous focal visual field loss.

We compare the focal structure-function correlation of structural measurements of peripapillary retinal nerve fiber layer thickness (RNFL-T) using optical coherence tomography (OCT), capillary density (CD) measurements using OCT-angiography (OCT-A), or a combination of both, with visual field deviation (VFD) in early to advanced glaucoma. Primary open angle glaucoma patients (n = 46, mean ± SD age: 67 ± 10 years; VF mean deviation: -10.41 ± 6.76 dB) were included in this cross-sectional study. We performed 30-2 standard automated perimetry OCT (3.5-mm diameter ring scan) and 15°×15° OCT-A (superficial vascular complex slab). Based on a nerve fiber trajectory model, each VF test spot was assigned to an OCT-A wedge and an OCT ring-sector. Two univariate linear models (Mv and Mt ) using either CD-based vascular (Mv ) or RNFL-T-based thickness information (Mt ) and one multivariate model using both (Mv:t ) were compared in their associations with measured focal VFD, which were higher for the multivariate model Mv:t (mean ± SD correlation coefficient: 0.710 ± 0.086) than for either nested model (0.627 ± 0.078 for Mv and 0.578 ± 0.095 for Mt ). Using a focal visual field approach, the combination of RNFL-T and CD showed better structure-function correlations than thickness or vascular information only.

Measuring optic nerve head perfusion to monitor glaucoma: a study on structure-function relationships using laser speckle flowgraphy.

PURPOSE: We aimed to describe the global and localized correlations among visual field (VF) sensitivity, optic nerve head (ONH) perfusion measured by laser speckle flowgraphy (LSFG) and neural structure measured by optical coherence tomography (OCT) in open-angle glaucoma (OAG) and to compare the floor effect for LSFG and OCT. METHODS: Cross-sectional, multicenter study including one eye each from fifty OAG patients (mean age 69.3 years; average VF mean deviation, MD, -8.5 dB, range -25.17 to 0.85 dB) and fifty-one controls. Patients underwent SITA standard 24-2 automated perimetry and measurement of ONH perfusion, peripapillary retinal nerve fibre layer thickness (RNFLT) and macular ganglion cell-inner plexiform layer thickness (GCIPLT). We tested the presence of a significant change (breakpoint) in the correlation slope with VF sensitivity to assess floor effect. RESULTS: The correlation between the LSFG parameter Mean All (MA) of the global disc area and MD (r = 0.56, p < 0.001) did not show a breakpoint, in contrast to the correlations between MD and OCT global parameters, which showed breakpoints at -8.53 and -4.05 dB for RNFLT and GCIPLT, respectively. Global and localized correlations with VF sensitivity were stronger for LSFG compared to OCT. In particular, LSFG outperformed OCT in the correlation with the central VF sector (r = 0.50, p < 0.001 and r = 0.06, p = 0.67 for MA and RNFLT, respectively). CONCLUSION: The global and sectoral correlations with VF sensitivity and the favourable floor effect compared to OCT indicate LSFG as a promising tool to monitor progression particularly in late-stage glaucoma. Further longitudinal studies are warranted.

Effect of hyperoxia and hypoxia on retinal vascular parameters assessed with optical coherence tomography angiography.

PURPOSE: To investigate the response of the superficial and deep capillary plexuses to hyperoxia and hypoxia using optical coherence tomography angiography (OCT-A) and retinal vessel analyzer. METHODS: Twenty-four healthy volunteers participated in this randomized, double-masked, cross-over study. For each subject, two study days were scheduled: on one study day, hyperoxia was induced by breathing 100% oxygen whereas on the other study day, hypoxia was induced by breathing a mixture of 88% nitrogen and 12% oxygen. Perfusion density was calculated in the superficial vascular plexus (SVP) and the deep capillary plexus (DCP), using OCT-A before (normal breathing) and during breathing of the gas mixtures. Retinal vessel calibres in major retinal vessels were measured using a dynamic vessel analyzer. RESULTS: During 100% oxygen breathing, a significant decrease in DCP perfusion density from 41.7 ± 2.4 a.u to 35.6 ± 3.1 a.u. (p < 0.001) was observed, which was accompanied by a significant decrease in vessel diameters in major retinal arteries and veins (p < 0.001 each). No significant change in perfusion density in the SVP occurred (p = 0.33). In contrast, during hypoxia, perfusion density in the SVP significantly increased from 34.4 ± 3.0 a.u. to 37.1 ± 2.2 a.u. (p < 0.001), while it remained stable in the DCP (p = 0.25). A significant increase in retinal vessel diameters was found (p < 0.01). Systemic oxygen saturation correlated negatively with perfusion density in the SVP and the DCP and retinal vessel diameters (p < 0.005 each). CONCLUSION: Our results show that systemic hyperoxia induces a significant decrease in vessel density in the DCP, while hypoxia leads to increased vessel density limited to the SVP. These results indicate that the retinal circulation shows the ability to adapt its blood flow to metabolic changes with high local resolution dependent on the capillary plexus.