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PURPOSE OF REVIEW: Degeneration of the maculopapillary bundle (MPB) is a prominent feature in a spectrum of optic neuropathies. MPB-selective degeneration is seen in specific conditions, such as nutritional and toxic optic neuropathies, Leber hereditary optic neuropathy (LHON), and dominant optic atrophy (DOA). Despite their distinct etiologies and clinical presentations, which encompass variations in age of incidence and monocular or binocular onset, these disorders share a core molecular mechanism: compromised mitochondrial homeostasis. This disruption is characterized by dysfunctions in mitochondrial metabolism, biogenesis, and protein synthesis. This article provides a comprehensive understanding of the MPB's role in optic neuropathies, emphasizing the importance of mitochondrial mechanisms in the pathogenesis of these conditions. RECENT FINDINGS: Optical coherence tomography studies have characterized the retinal nerve fiber layer changes accompanying mitochondrial-affiliated optic neuropathies. Selective thinning of the temporal optic nerve head is preceded by thickening in early stages of these disorders which correlates with reductions in macular ganglion cell layer thinning and vascular atrophy. A recently proposed mechanism underpinning the selective atrophy of the MPB involves the positive feedback of reactive oxygen species generation as a common consequence of mitochondrial dysfunction. Additionally, new research has revealed that the MPB can undergo degeneration in the early stages of glaucoma, challenging the historically held belief that this area was not involved in this common optic neuropathy. A variety of anatomical risk factors influence the propensity of glaucomatous MPB degeneration, and cases present distinct patterns of ganglion cell degeneration that are distinct from those observed in mitochondria-associated diseases. This review synthesizes clinical and molecular research on primary MPB disorders, highlighting the commonalities and differences in their pathogenesis. KEY POINTS (BOX): 1. Temporal degeneration of optic nerve fibers accompanied by cecocentral scotoma is a hallmark of maculopapillary bundle (MPB) degeneration. 2. Mechanisms of MPB degeneration commonly implicate mitochondrial dysfunction. 3. Recent research challenges the traditional belief that the MPB is uninvolved in glaucoma by showing degeneration in the early stages of this common optic neuropathy, yet with features distinct from other MPB-selective neuropathies. 4. Reactive oxygen species generation is a mechanism linking mitochondrial mechanisms of MPB-selective optic neuropathies, but in-vivo and in-vitro studies are needed to validate this hypothesis.
Subject(s)
Optic Nerve Diseases , Humans , Optic Nerve Diseases/pathologyABSTRACT
The 7th edition of the Canadian Stroke Best Practice Recommendations (CSBPR) is a comprehensive summary of current evidence-based recommendations, appropriate for use by healthcare providers and system planners, and intended to drive healthcare excellence, improved outcomes and more integrated health systems. This edition includes a new module on the management of cerebral venous thrombosis (CVT). Cerebral venous thrombosis is defined as thrombosis of the veins of the brain, including the dural venous sinuses and/or cortical or deep veins. Cerebral venous thrombosis is a rare but potentially life-threatening type of stroke, representing 0.5-1.0% of all stroke admissions. The reported rates of CVT are approximately 10-20 per million and appear to be increasing over time. The risk of CVT is higher in women and often associated with oral contraceptive use and with pregnancy and the puerperium. This guideline addresses care for adult individuals who present to the healthcare system with current or recent symptoms of CVT. The recommendations cover the continuum of care from diagnosis and initial clinical assessment of symptomatic CVT, to acute treatment of symptomatic CVT, post-acute management, person-centered care, special considerations in the long-term management of CVT, including pregnancy and considerations related to CVT in special circumstances such as trauma and vaccination. This module also includes supporting materials such as implementation resources to facilitate the adoption of evidence into practice and performance measures to enable monitoring of uptake and effectiveness of recommendations.
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Clinical Relevance: Visual function impairment from diabetic retinopathy can have a considerable impact on patient's quality of life. Best-corrected visual acuity (BCVA) is most commonly used to assess visual function and guide clinical trials. However, BCVA is affected late in the disease process, is not affected in early disease, and does not capture some of the visual disturbances described by patients with diabetes. The goal of this report is to evaluate the relationship between diabetic retinal disease (DRD) and visual function parameters to determine which if any of them may be used in a future DRD staging system. Methods: The visual functions working group was 1 of 6 areas of DRD studied as part of the DRD staging system update, a project of the Mary Tyler Moore Vision Initiative. The working group identified 12 variables of possible interest, 7 of which were judged to have sufficient preliminary data to suggest an association with DR to warrant further review: microperimetry, static automated perimetry, electroretinogram (ERG) oscillatory potentials, flicker ERG, low luminance visual acuity (LLVA), contrast sensitivity (CS), and BCVA. The objective field analyzer (OFA) was added after subsequent in-person workshops. Results: Currently, the only visual function test available for immediate use is BCVA; the remaining tests are either promising (within 5 years) or have potential (>5 years) use. Besides BCVA, most visual function tests had a limited role in current clinical care; however, LLVA, CS, flicker ERG, and OFA demonstrated potential for screening and research purposes. Conclusions: Although current visual function tests are promising, future prospective studies involving patients with early and more advanced retinopathy are necessary to determine if these tests can be used clinically or as endpoints for clinical studies. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
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Purpose: Axonal degeneration in acute and chronic disorders is well-characterized, comprising retrograde (proximal) and Wallerian (distal) degeneration, but the mechanism of propagation remains less understood. Methods: Laser injury with a diode-pumped solid-state 532 nm laser was used to axotomize retinal ganglion cell axons. We used confocal in vivo imaging to demonstrate that phosphatidylserine externalization is a biomarker of early axonal degeneration after selective intraretinal axotomy. Results: Quantitative dynamic analysis revealed that the rate of axonal degeneration was fastest within 40 minutes, then decreased exponentially afterwards. Axonal degeneration was constrained within the same axotomized axonal bundles. Remarkably, axon degeneration arising from the site of injury induced a secondary degeneration of distal normal axons. Conclusions: Axonal degeneration in vivo is a progressive process associated with phosphatidylserine externalization, which can propagate not only along the axon but to adjacent uninjured axons. This finding has implications for acute and chronic neurodegenerative disorders associated with axonal injury.
Subject(s)
Axons , Phosphatidylserines , Humans , Axons/pathology , Axotomy , Wallerian Degeneration/pathology , Retinal Ganglion Cells/pathologyABSTRACT
PURPOSE: We describe the baseline ophthalmic and cardiovascular risk factors across countries, race, and sex for the Quark207 treatment trial for acute nonarteritic anterior ischemic optic neuropathy (NAION). DESIGN: Prospective, randomized controlled clinical trial. PARTICIPANTS: Adults 50 to 80 years of age with acute NAION recruited from 80 sites across 8 countries. MAIN OUTCOME MEASURES: Ophthalmic features of NAION and cardiovascular risk factors. METHODS: We evaluated demographics and clinical and ophthalmologic data, including best-corrected visual acuity (BCVA) and average visual field total deviation (TD), in affected eyes and cup-to-disc ratio in fellow eyes at enrollment. We report the prevalence (mean and standard devition, and median and interquartile range [IQR]) of ophthalmic features and cardiovascular risk factors, stratified by country, race, and sex. We corrected for multiple comparisons using Dunn's test with Bonferroni correction for continuous variables and chi-square testing with Holm-Bonferroni correction for categorical variables. RESULTS: The study enrolled 500 men and 229 women with a median age of 60 and 61 years (P = 0.027), respectively. Participants were predominantly White (n = 570) and Asian (n = 149). The study eye BCVA was 71 characters (IQR, 53-84 characters; approximately 0.4 logarithm of the minimum angle of resolution), and the TD was -16.5 dB (IQR, -22.2 to -12.6 dB) for stimulus III and -15.7 dB (IQR, -20.8 to -10.9 dB) for stimulus V. The vertical and horizontal cup-to-disc ratio was 0.1 (IQR, 0.1-0.3) for unaffected fellow eyes. The prevalence of cardiovascular risk factors varied among countries. The most notable differences were in the baseline comorbidities and ophthalmologic features, which differed between Asian and White races. Men and women differed with respect to a few clinically meaningful features. CONCLUSIONS: The cardiovascular risk factors in the NAION cohort varied among the 7 countries, race, and sex, but were not typically more prevalent than in the general population. Ophthalmic features, typical of NAION, generally were consistent across countries, race, and sex, except for worse BCVA and TD in China. Men have a frequency of NAION twice that of women. Having a small cup-to-disc ratio in the fellow eye was the most prevalent risk factor across all demographics. This study suggests that factors, not yet identified, may contribute to the development of NAION. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.
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Optic Neuropathy, Ischemic , Visual Acuity , Visual Fields , Humans , Optic Neuropathy, Ischemic/physiopathology , Optic Neuropathy, Ischemic/diagnosis , Male , Female , Aged , Middle Aged , Prospective Studies , Visual Acuity/physiology , Aged, 80 and over , Acute Disease , Visual Fields/physiology , Risk Factors , Prevalence , Brimonidine Tartrate/therapeutic use , Brimonidine Tartrate/administration & dosage , Optic Disk/pathology , Ranibizumab/therapeutic use , Ranibizumab/administration & dosageABSTRACT
The translation of regenerative therapies to neuronal eye diseases requires a roadmap specific to the nature of the target diseases, patient population, methodologies for assessing outcome, and other factors. This commentary focuses on critical issues for translating regenerative eye therapies relevant to retinal neurons to human clinical trials.
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Eye Diseases , Retinal Neurons , Humans , Eye Diseases/therapy , TranslationsABSTRACT
Leber hereditary optic neuropathy (LHON) is a rare syndrome that results in vision loss. A necessary but not sufficient condition for its onset is the existence of known mitochondrial DNA mutations that affect complex I biomolecular structure. Cybrids with LHON mutations generate higher rates of reactive oxygen species (ROS). This study models how ROS, particularly H2O2, could signal and execute the axonal degeneration process that underlies LHON. We modeled and explored several hypotheses regarding the influence of H2O2 on the dynamics of propagation of axonal degeneration in LHON. Zonal oxidative stress, corresponding to H2O2 gradients, correlated with the morphology of injury exhibited in the LHON pathology. If the axonal membrane is highly permeable to H2O2 and oxidative stress induces larger production of H2O2, small injuries could trigger cascading failures of neighboring axons. The cellular interdependence created by H2O2 diffusion, and the gradients created by tissue variations in H2O2 production and scavenging, result in injury patterns and surviving axonal loss distributions similar to LHON tissue samples. Specifically, axonal degeneration starts in the temporal optic nerve, where larger groups of small diameter fibers are located and propagates from that region. These findings correlate well with clinical observations of central loss of visual field, visual acuity, and color vision in LHON, and may serve as an in silico platform for modeling the mechanism of action for new therapeutics.
Subject(s)
Optic Atrophy, Hereditary, Leber , Humans , Optic Atrophy, Hereditary, Leber/genetics , Optic Atrophy, Hereditary, Leber/pathology , Reactive Oxygen Species , Hydrogen Peroxide , Optic Nerve , DNA, Mitochondrial/genetics , MutationABSTRACT
OBJECTIVE: To collect information on the current equity, diversity, and inclusion (EDI) landscape at Canadian ophthalmology academic centres. DESIGN: Cross-sectional survey. PARTICIPANTS: Faculty representatives from 15 accredited Canadian ophthalmology postgraduate training programs and 57 ophthalmology resident survey respondents. METHOD: A three-phase virtual EDI initiative was conducted by the Association of Canadian University Professors of Ophthalmology in 2021. A qualitative survey of Canadian academic ophthalmology programs and an anonymous survey of Canadian ophthalmology residents were completed. RESULTS: All Canadian ophthalmology programs provided information on their current EDI strategies, yielding a response rate of 100%. The majority (73%) of Canadian academic ophthalmology centres identified as being in the beginning stages of building an EDI framework. Of the 57 responding resident physicians, 44% identified as a woman and 51% as a visible minority. There were no respondents who identified as Indigenous. Three respondents identified as having a disability per the Accessible Canada Act. Most respondents either agreed or strongly agreed that their programs are equal opportunity providers (80%), trustworthy (72%), respectful (74%), and of diverse opinions and ideas (71%). There were no statistically significant associations between responses to EDI questions and gender across population groups. CONCLUSIONS: Most Canadian ophthalmology academic centres are in the beginning stages of implementing EDI initiatives. Multiple priorities have been identified as areas for improvement, such as increasing EDI education for patients, learners, and physicians, and implementing EDI policies in selection and recruitment.
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Background: Neurological and ophthalmological neurodegenerative diseases in large part share underlying biology and pathophysiology. Despite extensive preclinical research on neuroprotection that in many cases bridges and unifies both fields, only a handful of neuroprotective therapies have succeeded clinically in either. Main body: Understanding the commonalities among brain and neuroretinal neurodegenerations can help develop innovative ways to improve translational success in neuroprotection research and emerging therapies. To do this, analysis of why translational research in neuroprotection fails necessitates addressing roadblocks at basic research and clinical trial levels. These include optimizing translational approaches with respect to biomarkers, therapeutic targets, treatments, animal models, and regulatory pathways. Conclusion: The common features of neurological and ophthalmological neurodegenerations are useful for outlining a path forward that should increase the likelihood of translational success in neuroprotective therapies.
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Membrane phospholipids are critical components of several signaling pathways. Maintained in a variety of asymmetric distributions, their trafficking across the membrane can be induced by intra-, extra-, and intercellular events. A familiar example is the externalization of phosphatidylserine from the inner leaflet to the outer leaflet in apoptosis, inducing phagocytosis of the soma. Recently, it has been recognized that phospholipids in the axonal membrane may be a signal for axonal degeneration, regeneration, or other processes. This review focuses on key recent developments and areas for ongoing investigations. KEY FACTS: Phosphatidylserine externalization propagates along an axon after axonal injury and is delayed in the Wallerian degeneration slow (WldS) mutant. The ATP8A2 flippase mutant has spontaneous axonal degeneration. Microdomains of axonal degeneration in spheroid bodies have differential externalization of phosphatidylserine and phosphatidylethanolamine. Phospholipid trafficking could represent a mechanism for coordinated axonal degeneration and elimination, i.e. axoptosis, analogous to apoptosis of the cell body.
Subject(s)
Phosphatidylserines , Phospholipids , Axons , Humans , Neurons , Wallerian DegenerationABSTRACT
Causes of blindness differ across the globe; in higher-income countries, most blindness results from the degeneration of specific classes of cells in the retina, including retinal pigment epithelium (RPE), photoreceptors, and retinal ganglion cells. Advances over the past decade in retinal regenerative medicine have allowed each of these cell types to be produced ex vivo from progenitor stem cells. Here, we review progress in applying these technologies to cell replacement - with the goal of vision restoration in degenerative disease. We discuss the landscape of human clinical trials for RPE transplantation and advanced preclinical studies for other cell types. We also review progress toward in situ repair of retinal degeneration using endogenous progenitor cells. Finally, we provide a high-level overview of progress toward prosthetic ocular vision restoration, including advanced photovoltaic devices, opsin-based gene therapy, and small-molecule photoswitches. Progress in each of these domains is at or near the human clinical-trial stage, bringing the audacious goal of vision restoration within sight.
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Retinal Degeneration , Stem Cell Transplantation , Blindness/therapy , Humans , Regenerative Medicine , Retina , Retinal Degeneration/therapy , Retinal Pigment Epithelium , Stem Cell Transplantation/methodsABSTRACT
The translation of promising preclinical research into successful trials often fails. One contributing factor is the "Princess and the Pea" problem, which refers to how an initially significant effect size dissipates as research transitions to more complex systems. This work aimed to quantify the effects of spreading variability on sample size requirements. Sample size estimates were performed by Monte Carlo simulation. To simulate the process of progressing from preclinical to clinical studies, nested sigmoidal dose-response transformations with modifiable input parameter variability were used. The results demonstrated that adding variabilty to the dose-response parameters substantially increases sample size requirements compared to standared calculations. Increasing the number of consecutive studies further increases the sample size. These results quantitatively demonstrate how the spread of variability in translational research, which is not typically accounted for, can result in drastic increases in the sample size required to maintain a desired study power.
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Research Design , Translational Research, Biomedical , Computer Simulation , Monte Carlo Method , Sample SizeABSTRACT
The loss of a spouse is a common and natural life event for older adults. Nearly one of four older bereaved spouses experience prolonged grief, impaired function or chronic depression. Mechanisms underlying these and other long-term health risks are not well understood. We conducted a scoping literature review to examine the interventions and outcomes that have been studied for late-life spousal bereavement to date. We identified 22 studies of group and individual-level interventions with most studies concerning grief processes within the first year. Nearly all studies evaluated emotional and psychological symptoms of loss and a small number evaluated the restoration of adaptive functioning. Four interventions addressed the treatment of complicated grief or grief with major depressive disorder. Qualitative studies explored themes of spirituality and mindfulness. There were 17 controlled studies, including 13 randomized controlled trials. Findings were eclectic, with evidence supporting mindfulness techniques in a group format for emotional and life satisfaction outcomes; an individual, function-based therapy addressing sleep to improve emotion and function; an individual, writing-based emotional expression therapy for short-term improvement in emotion and function; nortriptyline for the treatment of bereavement-related major depressive disorder; a group-based, complicated grief therapy for this condition; an internet-based CBT intervention for prolonged grief; and pharmacotherapy for cardiovascular changes during bereavement. These findings highlight the small literature of methodologically strong intervention studies addressing spousal bereavement in older adults and the need for greater exploration of relevant biological, social, cognitive and behavioral factors to improve short and long term health outcomes.
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Bereavement , Depressive Disorder, Major , Adaptation, Psychological , Aged , Depression/psychology , Depressive Disorder, Major/therapy , Grief , Humans , Spouses/psychologyABSTRACT
OBJECTIVES: Increasing evidence supports a bidirectional relationship between major depressive disorder (MDD) and obesity, but the role of visceral adipose tissue (VAT) as a measure of obesity in relation to MDD is not well understood. Here we review literature investigating the link between MDD and VAT in terms of biomarkers, sex differences, and aging. METHODS: PubMed, EMBASE, PsycINFO, and CINAHL searches were conducted on December 11, 2020. No date or language limits were imposed. Major concepts searched were Depressive Disorder linked with Adipose Tissue, White, Hypothalmo-Hypophyseal System, and Pituitary-Adrenal System in addition to keywords. A final set of 32 items meeting criteria for inclusion. RESULTS: Converging biological evidence suggests a significant bidirectional relationship between VAT and MDD across the lifespan. In adulthood, greater VAT was associated with increased risk for depression, especially in vulnerable groups such as individuals who are overweight/obese, postmenopausal women, and individuals with comorbid medical or psychiatric illness. In older adults, sarcopenia had an impact on the relationship between abnormal VAT and risk of depression. Additionally, sex differences emerged as a potential factor affecting the strength of the association between VAT and depression. CONCLUSIONS: Elucidating the pathophysiological mechanisms associated with increased rates of depression in obese individuals will be crucial for developing specific treatment strategies that seek to improve outcomes in individuals with comorbid depression and obesity. Moreover, identifying age- and sex-specific risk factors may contribute to a more personalized medicine approach, thereby improving the quality of clinical care.
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Bipolar Disorder , Depressive Disorder, Major , Adult , Aged , Depressive Disorder, Major/complications , Depressive Disorder, Major/epidemiology , Female , Humans , Intra-Abdominal Fat , Longevity , Male , ObesityABSTRACT
INTRODUCTION: The COVID-19 pandemic promoted hitherto unseen uptake of telemedicine by ophthalmologists. We performed a mixed methods study to explore patters of utilization during the pandemic and perceived future utility. METHODS: Ophthalmologists practicing in Canada between March and July 2020 were invited to complete an online questionnaire assessing demographics, clinical practice characteristics and telemedicine utilization prior to and during the pandemic. Descriptive and bivariate statistics were used to analyze the data. Agglomerative hierarchical cluster analysis was used to identify groups who varied on the types of visits offered using telemedicine. Ten one-on-one interviews were conducted and analyzed using thematic content analysis to explain trends observed in the survey data. RESULTS: Seventy-three ophthalmologists completed the survey. Six percent reported using telemedicine prior to the pandemic compared to 80% during the pandemic. A significant majority (81%) primarily used the telephone for telemedicine visits. Overall, visit volumes during the pandemic declined to 40% of pre-pandemic levels, with a smaller decline for ophthalmologists who used telemedicine than those who did not. Those who used telemedicine for all visit types were more likely to use telemedicine software and to anticipate a modest-to-large role for telemedicine in their future practice. DISCUSSION: For many ophthalmologists, integrating telemedicine into clinical practice may have partially offset the disruption to normal clinical activities during the pandemic. While the majority saw telemedicine as a temporary solution, a sizeable minority appear to have made considerable use of the technology and see an ongoing role for it once regular clinical activities resume.
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COVID-19 , Ophthalmologists , Telemedicine , Humans , COVID-19/epidemiology , Pandemics , SARS-CoV-2 , Telemedicine/methodsABSTRACT
Bedside ultrasound has been shown to change and direct patient management in the emergent setting. Demand, use, and diagnostic potential of point-of-care ultrasound (POCUS) has continually increased throughout the years. The ongoing COVID-19 pandemic and physical distancing have necessitated further POCUS innovation. With the advent of affordable portable ultrasound devices, teleultrasound teaching has become a more viable method of POCUS education, especially in resource-limited settings. Here, we provide a scoping review of the current state of teleultrasound, specifically its use for educational purposes.
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COVID-19 , Point-of-Care Systems , Curriculum , Humans , Pandemics , UltrasonographySubject(s)
Clinical Trials as Topic/methods , Endpoint Determination/methods , Optic Nerve Diseases/therapy , Patient Reported Outcome Measures , Consensus Development Conferences, NIH as Topic , Humans , National Eye Institute (U.S.) , Ophthalmology/organization & administration , Quality of Life , Societies, Medical/organization & administration , United StatesABSTRACT
Optic neuropathies such as glaucoma are characterized by retinal ganglion cell (RGC) degeneration and death. The sigma-1 receptor (S1R) is an attractive target for treating optic neuropathies as it is highly expressed in RGCs, and its absence causes retinal degeneration. Activation of the S1R exerts neuroprotective effects in models of retinal degeneration. Pridopidine is a highly selective and potent S1R agonist in clinical development. We show that pridopidine exerts neuroprotection of retinal ganglion cells in two different rat models of glaucoma. Pridopidine strongly binds melanin, which is highly expressed in the retina. This feature of pridopidine has implications to its ocular distribution, bioavailability, and effective dose. Mitochondria dysfunction is a key contributor to retinal ganglion cell degeneration. Pridopidine rescues mitochondrial function via activation of the S1R, providing support for the potential mechanism driving its neuroprotective effect in retinal ganglion cells.