Aqueous outflow imaging techniques and what they tell us about intraocular pressure regulation.

Recent advances in the medical and surgical management of open-angle glaucoma have increased the number of treatment options available. Several new intraocular pressure (IOP)-lowering treatments target the conventional aqueous outflow (AO) system. However, success rates are variable and outcomes in individual patients are often difficult to predict. Variable treatment responses remain unexplained and highlight deficiencies in our current understanding of AO regulation and IOP homeostasis. Imaging is often relied upon to confirm diagnoses and monitor treatment responses in other ocular and systemic pathologies. As yet no suitable AO imaging tool has been developed to fulfil this role in glaucoma. A variety of imaging techniques have been used to study the AO tracts of humans and animals in ex vivo and in vivo eyes. In this review, results from novel imaging techniques that assess aqueous drainage through the episcleral venous system are considered and we argue these provide new insights into AO regulation. We suggest that the ability to objectively measure AO responses to interventions would be a significant clinical advance, and we have demonstrated that this can be achieved with direct visualisation of aqueous drainage. We predict that the evolution of AO imaging technology will continue to reveal critical components of AO and IOP regulation, and that personalised IOP-lowering treatment in glaucoma care may well become a reality in the near future.1. A core support grant from the Wellcome Trust and MRC to the Wellcome Trust – Medical Research Council Cambridge Stem Cell Institute 2. Haemoglobin Video Imaging facilities funded by Sydney Eye Hospital Foundation, Carl Zeiss Meditec, and Glaukos Corporatio

Haemoglobin Video Imaging provides novel in vivo high-resolution imaging and quantification of human aqueous outflow in glaucoma patients

Purpose Non-invasive, detailed measurement of the dynamics of human aqueous outflow is difficult to achieve with currently available clinical tools. Here we used haemoglobin video imaging (HVI) to develop a technique to image and quantify human aqueous outflow non-invasively and in real time. Design A prospective observational study to describe characteristics of aqueous veins and a pilot prospective interventional feasibility study to develop quantification parameters. Subjects Participants and/or Controls: Patients were recruited from the Addenbrookes Hospital Glaucoma clinic. The observational study included 30 eyes and the pilot interventional feasibility study was performed on 8 eyes undergoing selective laser trabeculoplasty (SLT). Our SLT protocol also included the installation of pilocarpine and apraclonidine eye drops. Methods, Intervention, or Testing Participants underwent HVI alongside their usual clinic visit. Main Outcome Measures The change in cross sectional area (CSA) of the aqueous column (AQC) within episcleral veins was correlated with IOP reduction and change in visual field mean deviation before and after intervention. Fluctuations in contrast and pixel intensity of red blood cells in an aqueous vein were calculated to compare the flow rate before and after intervention using autocorrelation analysis. Results HVI enables the direct observation of aqueous flow into the vascular system. Aqueous is seen to centralise within a laminar venous column. Flow is pulsatile, and fluctuations of flow through globe pressure or compression of the aqueous vein are observed. There was a significant increase in the AQC following the administration of our SLT protocol (n=13; p<0.05). This correlated with the degree of IOP reduction (n=13; Pearson’s correlation coefficient 0.7; p=0.007) and the improvement in mean deviation (MD) observed post intervention (n=8; Pearson’s correlation coefficient 0.75; p=0.03). Autocorrelation analysis demonstrated a faster rate of decay in an aqueous vein following intervention indicating an increase in flow rate. Conclusions HVI can be incorporated into a routine clinic slit lamp examination to allow a detailed assessment and quantification of aqueous outflow in real time. It has the potential to be used to help target therapeutic interventions to improve aqueous outflow and further advance our understanding of aqueous outflow dysregulation in the pathogenesis of glaucoma.This work was supported by grants from Addenbrooke’s Charitable Trust, the HB Allen Charitable Trust, the Cambridge Eye Trust, the Jukes Glaucoma Research Fund and a core support grant from the Wellcome Trust and MRC to the Wellcome Trust – Medical Research Council Cambridge Stem Cell Institute

Hemoglobin Video Imaging Provides Novel In Vivo High-Resolution Imaging and Quantification of Human Aqueous Outflow in Patients with Glaucoma.

Purpose:Noninvasive, detailed measurement of the dynamics of human aqueous outflow is difficult to achieve with currently available clinical tools. We used hemoglobin video imaging (HVI) to develop a technique to image and quantify human aqueous outflow noninvasively and in real time. Design:A prospective observational study to describe characteristics of aqueous veins and a pilot prospective interventional feasibility study to develop quantification parameters. Participants:Patients were recruited from the Cambridge University Hospitals NHS Foundation Trust Glaucoma clinic. The observational study included 30 eyes, and the pilot interventional feasibility study was performed on 8 eyes undergoing selective laser trabeculoplasty (SLT). Our SLT protocol also included the installation of pilocarpine and apraclonidine eye drops. Methods:Participants underwent HVI alongside their usual clinic visit. Main Outcome Measures:The change in cross-sectional area (CSA) of the aqueous column within episcleral veins was correlated with intraocular pressure (IOP) reduction and change in visual field mean deviation (MD) before and after intervention. Fluctuations in contrast and pixel intensity of red blood cells in an aqueous vein were calculated to compare the flow rate before and after intervention using autocorrelation analysis. Results:Hemoglobin video imaging enables the direct observation of aqueous flow into the vascular system. Aqueous is seen to centralize within a laminar venous column. Flow is pulsatile, and fluctuations of flow through globe pressure or compression of the aqueous vein are observed. There was a significant increase in the aqueous column after the administration of our SLT protocol (n = 13; P < 0.05). This correlated with the degree of IOP reduction (n = 13; Pearson's correlation coefficient 0.7; P = 0.007) and the improvement in MD observed postintervention (n = 8; Pearson's correlation coefficient 0.75; P = 0.03). Autocorrelation analysis demonstrated a faster rate of decay in an aqueous vein after intervention, indicating an increase in flow rate. Conclusions:Hemoglobin video imaging can be incorporated into a routine clinic slit-lamp examination to allow a detailed assessment and quantification of aqueous outflow in real time. It has the potential to be used to help target therapeutic interventions to improve aqueous outflow and further advance our understanding of aqueous outflow dysregulation in the pathogenesis of glaucoma

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Neuroprotection in Glaucoma: Towards Clinical Trials and Precision Medicine.

Purpose: The eye is currently at the forefront of translational medicine and therapeutics. However, despite advances in technology, primary open-angle glaucoma remains the leading cause of irreversible blindness worldwide. Traditional intraocular pressure (IOP)-lowering therapies are often not sufficient to prevent progression to blindness, even in patients with access to high-quality healthcare. Neuroprotection strategies, which aim to boost the ability of target cells to withstand a pathological insult, have shown significant promise in animal models but none have shown clinically relevant efficacy in human clinical trials to date. We sought to evaluate the current status of neuroprotection clinical trials for glaucoma and identify limitations which have prevented translation of new glaucoma therapies to date.Methods: Literature searches identified English language references. Sources included MEDLINE, EMBASE, the Cochrane Library and Web of Science databases; reference lists of retrieved studies; and internet pages of relevant organisations, meetings and conference proceedings, and clinical trial registries.Results: We discuss six key neuroprotective strategies for glaucoma that have reached the clinical trial stage. Delivery of neurotrophic factors through gene therapy is also progressing towards glaucoma clinical trials. Refinements in trial design and the use of new modalities to define structural and functional endpoints may improve our assessment of disease activity and treatment efficacy. Advances in our understanding of compartmentalised glaucomatous degeneration and continued progress in the molecular profiling of glaucoma patients will enable us to predict individual risk and tailor treatment.Conclusion: New approaches to future glaucoma neuroprotection trials could improve the prospects for new glaucoma therapies. Glaucoma treatment tailored according to an individual's unique risk profile may become increasingly common in the future

The Effects of Trabecular Bypass Surgery on Conventional Aqueous Outflow, Visualized by Hemoglobin Video Imaging.

PRECIS: Hemoglobin Video Imaging (HVI) provides a noninvasive method to quantify aqueous outflow (AO) perioperatively. Trabecular bypass surgery (TBS) is able to improve, and in some cases re-establish, conventional AO. PURPOSE: The purpose of this study was to use HVI to illustrate and quantify effects of TBS on AO through the episcleral venous system. DESIGN: This is a prospective observational cohort study. PARTICIPANTS: Patients were recruited from Sydney Eye Hospital, Australia. The study included 29 eyes from 25 patients, 15 with glaucoma and 14 normal controls. TBS (iStent Inject) was performed on 14 glaucomatous eyes (9 combined phacoemulsification/TBS and 5 standalone TBS). Cataract surgery alone was performed on the remaining eye from the glaucoma group and 2 eyes from the control group. METHODS: We used HVI, a novel clinic-based tool, to visualize and quantify AO perioperatively during routine follow-up to 6 months. Angiographic blood flow patterns were observed within prominent aqueous veins on the nasal and temporal ocular surface. Aqueous column cross-section area (AqCA) was compared before and after surgery. MAIN OUTCOME MEASURES: AqCA, number of aqueous veins, intraocular pressure (IOP) before and after surgery, and number of IOP-lowering medications. RESULTS: Patients with glaucoma had reduced AqCA compared with normal controls (P=0.00001). TBS increased AqCA in 13 eyes at 1 month (n=14; P<0.002), suggesting improved AO. This effect was maintained at 6 months in 7 eyes (n=9, P≤0.05). All patients with unrecordable AO before surgery (n=3; 2 standalone TBS, 1 combined cataract/TBS) established measurable flow after TBS. IOP and/or medication burden became reduced in every patient undergoing TBS. Cataract surgery alone (n=3) increased AqCA in nasal and temporal vessels at 4 weeks after surgery. CONCLUSIONS: HVI provides a safe method for detecting and monitoring AO perioperatively in an outpatient setting. Improvement of AO into the episcleral venous system is expected after TBS and can be visualized with HVI. TBS is able to improve, and in some cases re-establish, conventional AO. Cataract surgery may augment this. Some aqueous veins were first seen after TBS and these patients had unstable postoperative IOP control, which possibly suggests reorganization of aqueous homeostatic mechanisms. HVI may confirm adequacy of surgery during short-term follow-up, but further work is required to assess the potential of HVI to predict surgical outcomes and assist with personalized treatment decisions.1. Haemoglobin Video Imaging facilities funded by Sydney Eye Hospital Foundation, Carl Zeiss Meditec, and Glaukos Corporation. 2. iStent Inject devices for standalone cases were donated by Glaukos Corporation. 3. A core support grant from the Wellcome Trust and MRC to the Wellcome Trust – Medical Research Council Cambridge Stem Cell Institute. 4. Cambridge Eye Trus

Haemoglobin Video Imaging provides novel in vivo high-resolution imaging and quantification of human aqueous outflow in glaucoma patients

Purpose Non-invasive, detailed measurement of the dynamics of human aqueous outflow is difficult to achieve with currently available clinical tools. Here we used haemoglobin video imaging (HVI) to develop a technique to image and quantify human aqueous outflow non-invasively and in real time. Design A prospective observational study to describe characteristics of aqueous veins and a pilot prospective interventional feasibility study to develop quantification parameters. Subjects Participants and/or Controls: Patients were recruited from the Addenbrookes Hospital Glaucoma clinic. The observational study included 30 eyes and the pilot interventional feasibility study was performed on 8 eyes undergoing selective laser trabeculoplasty (SLT). Our SLT protocol also included the installation of pilocarpine and apraclonidine eye drops. Methods, Intervention, or Testing Participants underwent HVI alongside their usual clinic visit. Main Outcome Measures The change in cross sectional area (CSA) of the aqueous column (AQC) within episcleral veins was correlated with IOP reduction and change in visual field mean deviation before and after intervention. Fluctuations in contrast and pixel intensity of red blood cells in an aqueous vein were calculated to compare the flow rate before and after intervention using autocorrelation analysis. Results HVI enables the direct observation of aqueous flow into the vascular system. Aqueous is seen to centralise within a laminar venous column. Flow is pulsatile, and fluctuations of flow through globe pressure or compression of the aqueous vein are observed. There was a significant increase in the AQC following the administration of our SLT protocol (n=13; p<0.05). This correlated with the degree of IOP reduction (n=13; Pearson’s correlation coefficient 0.7; p=0.007) and the improvement in mean deviation (MD) observed post intervention (n=8; Pearson’s correlation coefficient 0.75; p=0.03). Autocorrelation analysis demonstrated a faster rate of decay in an aqueous vein following intervention indicating an increase in flow rate. Conclusions HVI can be incorporated into a routine clinic slit lamp examination to allow a detailed assessment and quantification of aqueous outflow in real time. It has the potential to be used to help target therapeutic interventions to improve aqueous outflow and further advance our understanding of aqueous outflow dysregulation in the pathogenesis of glaucoma.This work was supported by grants from Addenbrooke’s Charitable Trust, the HB Allen Charitable Trust, the Cambridge Eye Trust, the Jukes Glaucoma Research Fund and a core support grant from the Wellcome Trust and MRC to the Wellcome Trust – Medical Research Council Cambridge Stem Cell Institute

Neuroprotection of retinal ganglion cells by a novel gene therapy construct that achieves sustained enhancement of brain-derived neurotrophic factor/tropomyosin-related kinase receptor-B signaling.

Previous studies have demonstrated that intravitreal delivery of brain-derived neurotrophic factor (BDNF) by injection of recombinant protein or by gene therapy can alleviate retinal ganglion cell (RGC) loss after optic nerve injury. BDNF gene therapy can improve RGC survival in experimental models of glaucoma, the leading cause of irreversible blindness worldwide. However, the therapeutic efficacy of BDNF supplementation alone is time limited at least in part due to BDNF receptor downregulation. Tropomyosin-related receptor kinase-B (TrkB) downregulation has been reported in many neurological diseases including glaucoma, potentially limiting the effect of sustained or repeated BDNF delivery.Here, we characterize a novel adeno-associated virus (AAV) gene therapy (AAV2 TrkB-2A-mBDNF) that not only increases BDNF production but also improves long-term neuroprotective signaling by increasing expression of the BDNF receptor (TrkB) within the inner retina. This approach leads to significant and sustained elevation of survival signaling pathways ERK and AKT within RGCs over 6 months and avoids the receptor downregulation which we observe with treatment with AAV2 BDNF alone. We validate the neuroprotective efficacy of AAV2 TrkB-2A-mBDNF in a mouse model of optic nerve injury, where it outperforms conventional AAV2 BDNF or AAV2 TrkB therapy, before showing powerful proof of concept neuroprotection of RGCs and axons in a rat model of chronic intraocular pressure (IOP) elevation. We also show that there are no adverse effects of the vector on retinal structure or function as assessed by histology and electroretinography in young or aged animals. Further studies are underway to explore the potential of this vector as a candidate for progression into clinical studies to protect RGCs in patients with glaucoma and progressive visual loss despite conventional IOP-lowering treatment.This work was supported by the Wellcome Trust (Pathfinder Award), the Midven Rainbow Seed Fund, Quethera Ltd, University of Cambridge Enterprise, the HB Allen Charitable Trust and the Cambridge Eye Trust

Receptor-ligand supplementation via a self-cleaving 2A peptide-based gene therapy promotes CNS axonal transport with functional recovery.

Gene replacement approaches are leading to a revolution in the treatment of previously debilitating monogenic neurological conditions. However, the application of gene therapy to complex polygenic conditions has been limited. Down-regulation or dysfunction of receptor expression in the disease state or in the presence of excess ligand has been shown to compromise therapeutic efficacy. Here, we offer evidence that combined overexpression of both brain-derived neurotrophic factor and its receptor, tropomyosin receptor kinase B, is more effective in stimulating axonal transport than either receptor administration or ligand administration alone. We also show efficacy in experimental glaucoma and humanized tauopathy models. Simultaneous administration of a ligand and its receptor by a single gene therapy vector overcomes several problems relating to ligand deficiency and receptor down-regulation that may be relevant to multiple neurodegenerative diseases. This approach shows promise as a strategy to target intrinsic mechanisms to improve neuronal function and facilitate repair

Peripapillary Hyper-Reflective Ovoid Mass-like Structures in Stickler syndrome.

PURPOSE: To report a previously undescribed finding of peripapillary hyper reflective ovoid mass-like structures (PHOMS) in Stickler Syndrome DESIGN: Non-comparative case series SUBJECTS: Participants, and/or Controls: 22 eyes with anomalous optic disc from 11 Stickler Syndrome patients were identified and imaged. METHODS: Intervention, or Testing: PHOMS were graded using enhanced depth imaging optical coherence tomography (EDI-OCT) according to the consensus recommendations of The Optic Disc Drusen Studies Consortium. All EDI-OCT scans were obtained using the Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) with a dense horizontal raster (15 × 10°, 97 sections) centred on the optic nerve head and graded by two independent assessors. In case of disagreement, the image was graded by a third assessor. The presence of any co-existing optic disc drusen was also assessed using EDI-OCT and autofluorescence. MAIN OUTCOME MEASURES: The presence of PHOMS, clinical characteristics and genetic mutations. RESULTS: A pilot sample of 22 eyes with phenotypic optic disc abnormalities from 11 Stickler Syndrome patients were identified and imaged. Eight patients were female and 3 were male. The mean age was 31 years (13-58 years). PHOMS were present in 91% (n=20 eyes) of imaged eyes. 70% (n=14 eyes) were type 1 Stickler Syndrome and 30% (n=6 eyes) were type 2 Stickler Syndrome. Five percent (n=1 eye) developed retinal detachment and 75% (n=15 eyes) had undergone 360o prophylactic retinopexy. 41% (n=9) of eyes with PHOMS were present in patients with co-existing hearing loss and 13.6% (n=3) had orofacial manifestation of Stickler Syndrome in the form of a cleft palate. Seventy-five percent (n=15 eyes) of patients with PHOMS reported joint laxity or symptoms of arthritis. No co-existing optic disc drusen were identified and raised intracranial pressure was also excluded after neurological investigation. CONCLUSION: These data suggest that PHOMS are a novel finding in Stickler Syndrome patients and should be considered when evaluating the optic nerves of these patients