Showing papers in "Investigative Ophthalmology & Visual Science in 2019"

IMI - Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies

Abstract: Purpose We provide a standardized set of terminology, definitions, and thresholds of myopia and its main ocular complications. Methods Critical review of current terminology and choice of myopia thresholds was done to ensure that the proposed standards are appropriate for clinical research purposes, relevant to the underlying biology of myopia, acceptable to researchers in the field, and useful for developing health policy. Results We recommend that the many descriptive terms of myopia be consolidated into the following descriptive categories: myopia, secondary myopia, axial myopia, and refractive myopia. To provide a framework for research into myopia prevention, the condition of "pre-myopia" is defined. As a quantitative trait, we recommend that myopia be divided into myopia (i.e., all myopia), low myopia, and high myopia. The current consensus threshold value for myopia is a spherical equivalent refractive error ≤ -0.50 diopters (D), but this carries significant risks of classification bias. The current consensus threshold value for high myopia is a spherical equivalent refractive error ≤ -6.00 D. "Pathologic myopia" is proposed as the categorical term for the adverse, structural complications of myopia. A clinical classification is proposed to encompass the scope of such structural complications. Conclusions Standardized definitions and consistent choice of thresholds are essential elements of evidence-based medicine. It is hoped that these proposals, or derivations from them, will facilitate rigorous, evidence-based approaches to the study and management of myopia.

IMI - Report on Experimental Models of Emmetropization and Myopia.

Abstract: The results of many studies in a variety of species have significantly advanced our understanding of the role of visual experience and the mechanisms of postnatal eye growth, and the development of myopia. This paper surveys and reviews the major contributions that experimental studies using animal models have made to our thinking about emmetropization and development of myopia. These studies established important concepts informing our knowledge of the visual regulation of eye growth and refractive development and have transformed treatment strategies for myopia. Several major findings have come from studies of experimental animal models. These include the eye's ability to detect the sign of retinal defocus and undergo compensatory growth, the local retinal control of eye growth, regulatory changes in choroidal thickness, and the identification of components in the biochemistry of eye growth leading to the characterization of signal cascades regulating eye growth and refractive state. Several of these findings provided the proofs of concepts that form the scientific basis of new and effective clinical treatments for controlling myopia progression in humans. Experimental animal models continue to provide new insights into the cellular and molecular mechanisms of eye growth control, including the identification of potential new targets for drug development and future treatments needed to stem the increasing prevalence of myopia and the vision-threatening conditions associated with this disease.

IMI - Interventions Myopia Institute: Interventions for Controlling Myopia Onset and Progression Report.

Abstract: Myopia has been predicted to affect approximately 50% of the world’s population based on trending myopia prevalence figures. Critical to minimizing the associated adverse visual consequences of complicating ocular pathologies are interventions to prevent or delay the onset of myopia, slow its progression, and to address the problem of mechanical instability of highly myopic eyes. Although treatment approaches are growing in number, evidence of treatment efficacy is variable. This article reviews research behind such interventions under four categories: optical, pharmacological, environmental (behavioral), and surgical. In summarizing the evidence of efficacy, results from randomized controlled trials have been given most weight, although such data are very limited for some treatments. The overall conclusion of this review is that there are multiple avenues for intervention worthy of exploration in all categories, although in the case of optical, pharmacological, and behavioral interventions for preventing or slowing progression of myopia, treatment efficacy at an individual level appears quite variable, with no one treatment being 100% effective in all patients. Further research is critical to understanding the factors underlying such variability and underlying mechanisms, to guide recommendations for combined treatments. There is also room for research into novel treatment options.

Exosomes Derived From Mesenchymal Stem Cells Modulate miR-126 to Ameliorate Hyperglycemia-Induced Retinal Inflammation Via Targeting HMGB1

Abstract: Purpose In this study, we aim to investigate whether mesenchymal stem cell (MSC)-derived exosomes (MSC-Exos) could regulate hyperglycemia-induced retinal inflammation by transferring microRNA-126 (miR-126). Methods MSC-Exos were isolated from the media of human umbilical cord-derived mesenchymal stem cells (hUCMSCs), and this isolation was followed by the transfer of miR-126. MSC-Exos or MSC-Exos overexpressing miR-126 were intravitreally injected into diabetic rats in vivo and were cocultured with high glucose-affected human retinal endothelial cells (HRECs) in vitro. Plasma samples were obtained from the vitreous of rats and from HREC cells after treatment for ELISA assay. Retinal sections were examined using immunohistochemistry. RT-PCR and Western blotting were conducted to assess the levels of high-mobility group box 1 (HMGB1), NLRP3 inflammasome, and NF-κB/P65 in retinas and HRECs. Results Our results showed that hyperglycemia greatly increased inflammation in diabetic rats or HRECs exposed to high glucose, increasing the levels of caspase-1, interleukin-1β (IL-1β) and IL-18. The administration of MSC-Exos could effectively reverse this reaction. Compared to control MSC-Exos, MSC-Exos overexpressing miR-126 more successfully suppressed the HMGB1 signaling pathway and suppressed inflammation in diabetic rats. The administration of miR-126-expressing MSC-Exos significantly reduced high glucose-induced HMGB1 expression and the activity of the NLRP3 inflammasome in HRECs. Conclusions miR-126 expression in MSC-Exos reduces hyperglycemia-induced retinal inflammation by downregulating the HMGB1 signaling pathway.

IMI - Myopia Genetics Report.

Abstract: The knowledge on the genetic background of refractive error and myopia has expanded dramatically in the past few years. This white paper aims to provide a concise summary of current genetic findings and defines the direction where development is needed. We performed an extensive literature search and conducted informal discussions with key stakeholders. Specific topics reviewed included common refractive error, any and high myopia, and myopia related to syndromes. To date, almost 200 genetic loci have been identified for refractive error and myopia, and risk variants mostly carry low risk but are highly prevalent in the general population. Several genes for secondary syndromic myopia overlap with those for common myopia. Polygenic risk scores show overrepresentation of high myopia in the higher deciles of risk. Annotated genes have a wide variety of functions, and all retinal layers appear to be sites of expression. The current genetic findings offer a world of new molecules involved in myopiagenesis. As the missing heritability is still large, further genetic advances are needed. This Committee recommends expanding large-scale, in-depth genetic studies using complementary big data analytics, consideration of gene-environment effects by thorough measurement of environmental exposures, and focus on subgroups with extreme phenotypes and high familial occurrence. Functional characterization of associated variants is simultaneously needed to bridge the knowledge gap between sequence variance and consequence for eye growth.

Changes in Choroidal Thickness and Choroidal Blood Perfusion in Guinea Pig Myopia.

Abstract: Purpose The purpose of this study was to study changes in choroidal thickness (ChT) and choroidal blood perfusion (ChBP), and the correlation between them, in guinea pig myopia. Methods The reliability of optical coherence tomography angiography (OCTA) for measuring ChT and ChBP was verified in guinea pigs, after cervical dislocation (n = 7) or temporal ciliary artery transection (n = 6). Changes in refraction, axial length, ChT, and ChBP were measured during spontaneous myopia (n = 9), monocular form-deprivation myopia (FDM, n = 13), or lens-induced myopia (LIM, n = 14), and after 4 days of recovery from FDM and LIM. Results The abolition (by cervical dislocation) or reduction (by temporal ciliary artery transection) of ChBP, and of the associated changes in ChT, were verified by OCTA, thus validating the method of measurement. In the spontaneous myopia group, ChT and ChBP were reduced by 25.2% and 31.9%, respectively. In FDM eyes, mean ± SD ChT and ChBP decreased significantly compared with the untreated fellow eyes (ChT fellow: 76.13 ± 9.34 μm versus 64.76 ± 11.15 μm for FDM; ChBP fellow: 37.87 ± 6.37 × 103 versus 30.27 ± 6.06 × 103 for FDM) and increased after 4 days of recovery (ChT: 77.94 ± 12.57 μm; ChBP: 37.41 ± 6.11 × 103). Effects of LIM were similar to those of FDM. Interocular differences in ChT and ChBP were significantly correlated in each group (FDM: R = 0.71, P < 0.001; LIM: R = 0.53, P < 0.001). Conclusions ChT and ChBP were significantly decreased in all three models of guinea pig myopia, and they both increased during recovery. Changes in ChT were positively correlated with changes in ChBP. Therefore, it is possible that the changes of ChT are responsible for the changes of ChBP or vice versa.

IMI - Clinical Management Guidelines Report.

Abstract: Best practice clinical guidelines for myopia control involve an understanding of the epidemiology of myopia, risk factors, visual environment interventions, and optical and pharmacologic treatments, as well as skills to translate the risks and benefits of a given myopia control treatment into lay language for both the patient and their parent or caregiver. This report details evidence-based best practice management of the pre-, stable, and the progressing myope, including risk factor identification, examination, selection of treatment strategies, and guidelines for ongoing management. Practitioner considerations such as informed consent, prescribing off-label treatment, and guides for patient and parent communication are detailed. The future research directions of myopia interventions and treatments are discussed, along with the provision of clinical references, resources, and recommendations for continuing professional education in this growing area of clinical practice.

IMI - Myopia Control Reports Overview and Introduction.

Abstract: With the growing prevalence of myopia, already at epidemic levels in some countries, there is an urgent need for new management approaches. However, with the increasing number of research publications on the topic of myopia control, there is also a clear necessity for agreement and guidance on key issues, including on how myopia should be defined and how interventions, validated by well-conducted clinical trials, should be appropriately and ethically applied. The International Myopia Institute (IMI) reports the critical review and synthesis of the research evidence to date, from animal models, genetics, clinical studies, and randomized controlled trials, by more than 85 multidisciplinary experts in the field, as the basis for the recommendations contained therein. As background to the need for myopia control, the risk factors for myopia onset and progression are reviewed. The seven generated reports are summarized: (1) Defining and Classifying Myopia, (2) Experimental Models of Emmetropization and Myopia, (3) Myopia Genetics, (4) Interventions for Myopia Onset and Progression, (5) Clinical Myopia Control Trials and Instrumentation, (6) Industry Guidelines and Ethical Considerations for Myopia Control, and (7) Clinical Myopia Management Guidelines.

IMI - Clinical Myopia Control Trials and Instrumentation Report.

Abstract: The evidence-basis based on existing myopia control trials along with the supporting academic literature were reviewed; this informed recommendations on the outcomes suggested from clinical trials aimed at slowing myopia progression to show the effectiveness of treatments and the impact on patients. These outcomes were classified as primary (refractive error and/or axial length), secondary (patient reported outcomes and treatment compliance), and exploratory (peripheral refraction, accommodative changes, ocular alignment, pupil size, outdoor activity/lighting levels, anterior and posterior segment imaging, and tissue biomechanics). The currently available instrumentation, which the literature has shown to best achieve the primary and secondary outcomes, was reviewed and critiqued. Issues relating to study design and patient selection were also identified. These findings and consensus from the International Myopia Institute members led to final recommendations to inform future instrumentation development and to guide clinical trial protocols.

Prevention and Management of Myopia and Myopic Pathology.

Abstract: Myopia is fast becoming a global public health burden with its increasing prevalence, particularly in developed countries. Globally, the prevalence of myopia and high myopia (HM) is 28.3% and 4.0%, respectively, and these numbers are estimated to increase to 49.8% for myopia and 9.8% for HM by 2050 (myopia defined as -0.50 diopter [D] or less, and HM defined as -5.00 D or less). The burden of myopia is tremendous, as adults with HM are more likely to develop pathologic myopia (PM) changes that can lead to blindness. Accordingly, preventive measures are necessary for each step of myopia progression toward vision loss. Approaches to prevent myopia-related blindness should therefore attempt to prevent or delay the onset of myopia among children by increased outdoor time; retard progression from low/mild myopia to HM, through optical (e.g., defocus incorporated soft contact lens, orthokeratology, and progressive-additional lenses) and pharmacological (e.g., low dose of atropine) interventions; and/or retard progression from HM to PM through medical/surgical treatments (e.g., anti-VEGF therapies, macula buckling, and scleral crosslinking). Recent clinical trials aiming for retarding myopia progression have shown encouraging results. In this article, we highlight recent findings on preventive and early interventional measures to retard myopia, and current and novel treatments for PM.

Single-Cell RNA Transcriptome Helps Define the Limbal/Corneal Epithelial Stem/Early Transit Amplifying Cells and How Autophagy Affects This Population

Abstract: Purpose Single-cell RNA-sequencing (scRNA-seq) was used to interrogate the relatively rare stem (SC) and early transit amplifying (TA) cell populations in limbal/corneal epithelia from wild-type and autophagy-compromised mice. Methods We conducted scRNA-seq on ocular anterior segmental tissue from wild-type and beclin 1-deficient (beclin1+/-) mice, using a 10X Gemomics pipeline. Cell populations were distinguished by t-distributed stochastic neighbor embedding. Seurat analysis was conducted to compare gene expression profiles between these two groups of mice. Differential protein expression patterns were validated by immunofluorescence staining and immunoblotting. Results Unbiased clustering detected 10 distinct populations: three clusters of mesenchymal and seven clusters of epithelial cells, based on their unique molecular signatures. A discrete group of mesenchymal cells expressed genes associated with corneal stromal SCs. We identified three limbal/corneal epithelial cell subpopulations designated as stem/early TA, mature TA, and differentiated corneal epithelial cells. Thioredoxin-interacting protein and PDZ-binding kinase (PBK) were identified as novel regulators of stem/early TA cell quiescence. PBK arrested corneal epithelial cells in G2/M phase of the cell cycle. Beclin1+/- mice displayed a decrease in proliferation-associated (Ki67, Lrig1) and stress-response (H2ax) genes. The most increased gene in beclin1+/- mice was transcription factor ATF3, which negatively regulates limbal epithelial cell proliferation. Conclusions Establishment of a comprehensive atlas of genes expressed by stromal and epithelial cells from limbus and cornea forms the foundation for unraveling regulatory networks among these distinct tissues. Similarly, scRNA-seq profiling of the anterior segmental epithelia from wild-type and autophagy-deficient mice provides new insights into how autophagy influences proliferation in these tissues.

An Artificial Intelligence Approach to Detect Visual Field Progression in Glaucoma Based on Spatial Pattern Analysis.

Abstract: Purpose To detect visual field (VF) progression by analyzing spatial pattern changes. Methods We selected 12,217 eyes from 7360 patients with at least five reliable 24-2 VFs and 5 years of follow-up with an interval of at least 6 months. VFs were decomposed into 16 archetype patterns previously derived by artificial intelligence techniques. Linear regressions were applied to the 16 archetype weights of VF series over time. We defined progression as the decrease rate of the normal archetype or any increase rate of the 15 VF defect archetypes to be outside normal limits. The archetype method was compared with mean deviation (MD) slope, Advanced Glaucoma Intervention Study (AGIS) scoring, Collaborative Initial Glaucoma Treatment Study (CIGTS) scoring, and the permutation of pointwise linear regression (PoPLR), and was validated by a subset of VFs assessed by three glaucoma specialists. Results In the method development cohort of 11,817 eyes, the archetype method agreed more with MD slope (kappa: 0.37) and PoPLR (0.33) than AGIS (0.12) and CIGTS (0.22). The most frequently progressed patterns included decreased normal pattern (63.7%), and increased nasal steps (16.4%), altitudinal loss (15.9%), superior-peripheral defect (12.1%), paracentral/central defects (10.5%), and near total loss (10.4%). In the clinical validation cohort of 397 eyes with 27.5% of confirmed progression, the agreement (kappa) and accuracy (mean of hit rate and correct rejection rate) of the archetype method (0.51 and 0.77) significantly (P < 0.001 for all) outperformed AGIS (0.06 and 0.52), CIGTS (0.24 and 0.59), MD slope (0.21 and 0.59), and PoPLR (0.26 and 0.60). Conclusions The archetype method can inform clinicians of VF progression patterns.

miR-590-3p Inhibits Pyroptosis in Diabetic Retinopathy by Targeting NLRP1 and Inactivating the NOX4 Signaling Pathway

Abstract: Purpose To elucidate the mechanism whereby miR-590-3p regulates pyroptosis in diabetic retinopathy (DR). Methods Human retinal microvascular endothelial cells (HRMECs) incubated with high glucose (HG) were used to establish cell models, and the expression levels of miR-590-3p, caspase-1, IL-1β, NLRP1, NOX4, TXNIP, NLRP3, and ROS were determined. Additionally, miR-590-3p was altered using a mimic or an inhibitor, and siRNAs targeting NLRP1 and NOX4 were applied to explore the regulatory mechanism of miR-590-3p in DR. The relationships between miR-590-3p and NLRP1/NOX4 also were investigated using a luciferase reporter assay. Furthermore, vitreous tissue samples were collected to confirm pyroptosis in clinical DR. Results Downregulated miR-590-3p and upregulated NLRP1/NOX4 levels were observed in a cell culture model of DR. Inhibiting miR-590-3p upregulated NLRP1, the NOX4/ROS/TXNIP/NLRP3 pathway, and caspase-1. NLRP1 and NOX4 were confirmed as direct target genes of miR-590-3p. The overexpression of miR-590-3p or knockdown of NLRP1 and NOX4 increased cell activity and suppressed pyroptosis. Intriguingly, the upregulation of IL-1β induced the downregulation of miR-590-3p by lowering the DNA promoter activity of pri-miR-590. Conclusions HG induced pyroptosis in a cell culture model of DR, and the downregulation of miR-590-3p promoted pyroptotic death by targeting NLRP1 and activating the NOX4/ROS/TXNIP/NLRP3 pathway via an IL-1β-mediated positive feedback loop.

Deep Learning for Prediction of AMD Progression: A Pilot Study.

Abstract: Purpose To develop and assess a method for predicting the likelihood of converting from early/intermediate to advanced wet age-related macular degeneration (AMD) using optical coherence tomography (OCT) imaging and methods of deep learning. Methods Seventy-one eyes of 71 patients with confirmed early/intermediate AMD with contralateral wet AMD were imaged with OCT three times over 2 years (baseline, year 1, year 2). These eyes were divided into two groups: eyes that had not converted to wet AMD (n = 40) at year 2 and those that had (n = 31). Two deep convolutional neural networks (CNN) were evaluated using 5-fold cross validation on the OCT data at baseline to attempt to predict which eyes would convert to advanced AMD at year 2: (1) VGG16, a popular CNN for image recognition was fine-tuned, and (2) a novel, simplified CNN architecture was trained from scratch. Preprocessing was added in the form of a segmentation-based normalization to reduce variance in the data and improve performance. Results Our new architecture, AMDnet, with preprocessing, achieved an area under the receiver operating characteristic (ROC) curve (AUC) of 0.89 at the B-scan level and 0.91 for volumes. Results for VGG16, an established CNN architecture, with preprocessing were 0.82 for B-scans/0.87 for volumes versus 0.66 for B-scans/0.69 for volumes without preprocessing. Conclusions A CNN with layer segmentation-based preprocessing shows strong predictive power for the progression of early/intermediate AMD to advanced AMD. Use of the preprocessing was shown to improve performance regardless of the network architecture.

Macular Vessel Density Measured With Optical Coherence Tomography Angiography and Its Associations in a Large Population-Based Study

Abstract: Purpose We investigate macular perfusion and the systemic and ocular associations in a population-based setting. Methods In this cross-sectional study, 2018 adults residing in Hong Kong underwent detailed ophthalmic examinations after consenting to participate. Macular perfusion was measured with optical coherence tomography angiography (OCTA) using the split-spectrum amplitude decorrelation angiography algorithm. The parafoveal flow index and vessel area density were quantified using automated custom-built software. Results Of the 2018 participants, the OCTA measurements were available for 1940, and 1631 (84.1%) had good quality scans. The right eyes of these 1631 participants (43.1% men) were included for final analysis. Mean age was 49.8 years (range, 18-92 years). Mean global macular vessel density was 47.3% and 55.1% for the superficial and deep retinal layers, respectively. In multivariate analysis, lower superficial vessel density remained significantly associated with lower signal strength index (SSI; P < 0.001, standardized β = 0.607) and male sex (P < 0.001, β = 0.162), and borderline associated with older age (P = 0.09, β = -0.045) and longer axial length (AL; P = 0.09, β = -0.037), while lower deep layer vessel density was significantly associated with lower SSI (P < 0.001, standardized β = 0.667), longer AL (P < 0.001, β = -0.097), and higher creatinine (P < 0.001, β = -0.072). Conclusions This large population-based study provided normative OCTA data of macular vessel density and demonstrated that a lower superficial retinal vessel density was significantly associated with lower SSI and male sex, while a lower deep layer retinal vessel density was significantly associated with lower SSI, longer AL, and higher level of creatinine. These associations must be considered when interpreting clinical quantitative OCTA data.

Axial Growth and Lens Power Loss at Myopia Onset in Singaporean Children.

Abstract: Purpose We studied biometry changes before and after myopia onset in a cohort of Singaporean children. Methods All data were taken from the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). Participants underwent refraction and biometry measurements with a follow-up of 3 to 6 years. The longitudinal ocular biometry (spherical equivalent refraction, axial length, and lens power) changes were compared between children who suffered myopia during the study (N = 303), emmetropic children (N = 490), and children myopic at baseline (N = 509). Results At myopia onset, the myopic shift increased to 0.50 diopters (D)/y or more in new myopes compared to the minor changes in emmetropes of the same age. New myopes had higher axial growth rates than emmetropes, even years before myopia onset (0.37 and 0.14 mm/y, respectively; ANOVA with Bonferroni post hoc test, P < 0.001). After onset, the change in both parameters slowed down gradually, but significantly (P < 0.05). In new myopes, lens power loss (-0.71 D/y) was significantly higher up to 1 year before myopia onset compared to emmetropes (-0.46 D/y), after which lens power loss slows down rapidly. At age 7 years, (future) new myopes had lens power values close to those of emmetropes (25.12 and 25.23 D, respectively), while later these values approached those of children who were myopic at baseline (23.06 and 22.79 D, respectively, compared to 23.71 D for emmetropes; P < 0.001). Conclusions New myopes have higher axial growth rates and lens power loss before myopia onset than persistent emmetropes.

Comparison of Retinal Microvasculature in Patients With Alzheimer's Disease and Primary Open-Angle Glaucoma by Optical Coherence Tomography Angiography.

Abstract: Purpose Comparison of retinal microvasculature within the macula and the optic nerve head in the eyes of patients with Alzheimer's disease (AD), primary open-angle glaucoma (POAG), and in a healthy control (HC) group, using optical coherence tomography angiography (OCTA). Methods In this cross-sectional study, 27 patients with AD, 27 with POAG, and 27 healthy controls were enrolled. The Mini-Mental State Examination test was used to assess cognitive function. Ophthalmic examination included OCTA, which was used for the imaging of vascular flow within the layer of radial peripapillary capillaries (RPCs), and also in the superficial vascular plexus (SVP) and deep vascular plexus (DVP) of the retina. Results In the AD group, the density of vessels in DVP was significantly reduced and the foveal avascular zone was increased when compared to POAG and HC groups (P < 0.001). Patients with POAG had a significantly reduced vessel density in RPCs and SVP as compared to AD and HC groups (P < 0.001). The average thickness of peripapillary retinal nerve fiber layer was correlated with the vessel density in SVP in patients with POAG (Pearson's r = 0.66; P = 0.0002) and was significantly lower in POAG and AD groups than in the HC group (P < 0.001). Conclusions AD and POAG are neurodegenerative diseases associated with apoptosis of nerve cells and impairment of microvasculature. Despite the fact that in both diseases there are abnormalities of the entire retinal vascular system, significant microcirculatory impairment in POAG patients affects superficial vessels, whereas in AD patients it affects vessels located in the deeper retinal layers.

The Relationship Between Ambient Atmospheric Fine Particulate Matter (PM2.5) and Glaucoma in a Large Community Cohort

Abstract: Purpose Glaucoma is more common in urban populations than in others. Ninety percent of the world's population are exposed to air pollution above World Health Organization (WHO) recommended limits. Few studies have examined the association between air pollution and glaucoma. Methods Questionnaire data, ophthalmic measures, and ambient residential area air quality data for 111,370 UK Biobank participants were analyzed. Particulate matter with an aerodynamic diameter < 2.5 μm (PM2.5) was selected as the air quality exposure of interest. Eye measures included self-reported glaucoma, intraocular pressure (IOP), and average thickness of macular ganglion cell-inner plexiform layer (GCIPL) across nine Early Treatment Diabetic Retinopathy Study (ETDRS) retinal subfields as obtained from spectral-domain optical coherence tomography. We examined the associations of PM2.5 concentration with self-reported glaucoma, IOP, and GCIPL. Results Participants resident in areas with higher PM2.5 concentration were more likely to report a diagnosis of glaucoma (odds ratio = 1.06, 95% confidence interval [CI] = 1.01-1.12, per interquartile range [IQR] increase P = 0.02). Higher PM2.5 concentration was also associated with thinner GCIPL (β = -0.56 μm, 95% CI = -0.63 to -0.49, per IQR increase, P = 1.2 × 10-53). A dose-response relationship was observed between higher levels of PM2.5 and thinner GCIPL (P < 0.001). There was no clinically relevant relationship between PM2.5 concentration and IOP. Conclusions Greater exposure to PM2.5 is associated with both self-reported glaucoma and adverse structural characteristics of the disease. The absence of an association between PM2.5 and IOP suggests the relationship may occur through a non-pressure-dependent mechanism, possibly neurotoxic and/or vascular effects.

Composition and Diversity of Bacterial Community on the Ocular Surface of Patients With Meibomian Gland Dysfunction.

Abstract: Purpose To investigate the composition and diversity of bacterial community on the ocular surface of patients with meibomian gland dysfunction (MGD) via 16S rDNA sequencing. Methods Forty-seven patients with MGD, who were divided into groups of mild, moderate, and severe MGD, and 42 sex- and age-matched participants without MGD (control group) were enrolled. Samples were collected from the upper and lower conjunctival sac of one randomly chosen eye of each participant. Through sequencing the hypervariable region of 16S rDNA gene obtained from samples, differences in the taxonomy and diversity between groups were compared. Results Principle coordinate analysis showed significantly distinct clustering of the conjunctival sac bacterial community between the severe MGD group and the other groups. At the phylum level, the relative abundances of Firmicutes (31.70% vs. 19.67%) and Proteobacteria (27.46% vs. 14.66%) were significantly higher (P < 0.05, Mann-Whitney U), and the abundance of Actinobacteria (34.17% vs. 56.98%) was lower in MGD than controls (P < 0.05, Mann-Whitney U). At the genus level, the abundances of Staphylococcus (20.71% vs. 7.88%) and Sphingomonas (5.73% vs. 0.79%) in patients with MGD were significantly higher than the controls (P < 0.05, Mann-Whitney U), while the abundance of Corynebacterium (20.22% vs. 46.43%) was significantly lower (P < 0.05, Mann-Whitney U). The abundance of Staphylococcus was positively correlated with the meiboscores in patients with MGD (r = 0.650, P < 0.001, Spearman). Conclusions Patients with MGD can have various degrees of bacterial microbiota imbalance in the conjunctival sac. Staphylococcus, Corynebacterium, and Sphingomonas may play roles in the pathophysiology of MGD.

Age-related alterations in retinal tissue perfusion and volumetric vessel density

Abstract: Purpose To determine age-related alterations in the retinal tissue perfusion (RTP) and volumetric vessel density (VVD) in healthy subjects. Methods Total 148 healthy subjects (age 18 to 83 years) were enrolled and divided into four groups (G1, <35 years; G2, 35 ∼ 49 years; G3, 50 ∼ 64 years; and G4, ≥65 years). The RTP and VVD were measured at the macula. The RTP was calculated as the blood flow supplying the macular area (ϕ 2.5 mm) divided by the perfused tissue volume of the inner retina from the inner limiting membrane to the outer plexiform layer. The VVD of the macula (ϕ 2.5 mm) was calculated as the vessel density divided by the corresponding tissue volume. Results The RTP and VVD of the retinal vascular network and deep vascular plexus (DVP) reached a peak in G2. Compared to G2, G4 had significantly lower RTP and VVD of DVP (P < 0.05). After 35 years old, age was negatively related to the RTP (r = -0.26, P = 0.02) and VVD of the DVP (r = -0.47, P < 0.001). However, age was positively related to VVD of the superficial vascular plexus (SVP; r = 0.24, P = 0.04) in subjects aged more than 35 years. The RTP was correlated to VVD measurements (r = 0.23-0.37, P < 0.01). Conclusions This is the first study to reveal the age-related alterations in the RTP and VVD during normal aging in a healthy population. Decreased RTP and VVD in the DVP along with increased VVD in the SVP may represent a characteristic pattern of normal aging in the healthy population.

Disruption of Intestinal Homeostasis and Intestinal Microbiota During Experimental Autoimmune Uveitis

Abstract: Purpose We determine the changes in intestinal microbiota and/or disruptions in intestinal homeostasis during uveitis. Methods Experimental autoimmune uveitis (EAU) was induced in B10.RIII mice with coadministration of interphotoreceptor retinoid-binding protein peptide (IRBP) and killed mycobacterial antigen (MTB) as an adjuvant. Using 16S rRNA gene sequencing, we looked at intestinal microbial differences during the course of uveitis, as well as intestinal morphologic changes, changes in intestinal permeability by FITC-dextran leakage, antimicrobial peptide expression in the gastrointstinal tract, and T lymphocyte prevalence before and at peak intraocular inflammation. Results We demonstrate that increased intestinal permeability and antimicrobial peptide expression in the intestinal tract coincide in timing with increased effector T cells in the mesenteric lymph nodes, during the early stages of uveitis, before peak inflammation. Morphologic changes in the intestine were most prominent during this phase, but also occurred with adjuvant MTB alone, whereas increased intestinal permeability was found only in IRBP-immunized mice that develop uveitis. We also demonstrate that the intestinal microbiota were altered during the course of uveitis, and that some of these changes are specific to uveitic animals, whereas others are influenced by adjuvant MTB alone. Intestinal permeability peaked at 2 weeks, coincident with an increase in intestinal bacterial strain differences, peak lipocalin production, and peak uveitis. Conclusions An intestinal dysbiosis accompanies a disruption in intestinal homeostasis in autoimmune uveitis, although adjuvant MTB alone promotes intestinal disruption as well. This may indicate a novel axis for future therapeutic targeting experimentally or clinically.

Deep Learning Predicts OCT Measures of Diabetic Macular Thickening From Color Fundus Photographs.

Abstract: Purpose To develop deep learning (DL) models for the automatic detection of optical coherence tomography (OCT) measures of diabetic macular thickening (MT) from color fundus photographs (CFPs). Methods Retrospective analysis on 17,997 CFPs and their associated OCT measurements from the phase 3 RIDE/RISE diabetic macular edema (DME) studies. DL with transfer-learning cascade was applied on CFPs to predict time-domain OCT (TD-OCT)-equivalent measures of MT, including central subfield thickness (CST) and central foveal thickness (CFT). MT was defined by using two OCT cutoff points: 250 μm and 400 μm. A DL regression model was developed to directly quantify the actual CFT and CST from CFPs. Results The best DL model was able to predict CST ≥ 250 μm and CFT ≥ 250 μm with an area under the curve (AUC) of 0.97 (95% confidence interval [CI], 0.89-1.00) and 0.91 (95% CI, 0.76-0.99), respectively. To predict CST ≥ 400 μm and CFT ≥ 400 μm, the best DL model had an AUC of 0.94 (95% CI, 0.82-1.00) and 0.96 (95% CI, 0.88-1.00), respectively. The best deep convolutional neural network regression model to quantify CST and CFT had an R2 of 0.74 (95% CI, 0.49-0.91) and 0.54 (95% CI, 0.20-0.87), respectively. The performance of the DL models declined when the CFPs were of poor quality or contained laser scars. Conclusions DL is capable of predicting key quantitative TD-OCT measurements related to MT from CFPs. The DL models presented here could enhance the efficiency of DME diagnosis in tele-ophthalmology programs, promoting better visual outcomes. Future research is needed to validate DL algorithms for MT in the real-world.

Dysregulated Tear Fluid Nociception-Associated Factors, Corneal Dendritic Cell Density, and Vitamin D Levels in Evaporative Dry Eye.

Abstract: Purpose The purpose of this study was to study the status and association among tear-soluble factors, corneal dendritic cell density, vitamin D, and signs and symptoms in dry eye disease (DED). Methods A total of 33 control subjects and 47 evaporative dry eye patients were included in the study. DED diagnosis and classification was based on the 2017 Report of the Tear Film & Ocular Surface Society International Dry Eye Workshop (TFOS DEWS II). DED workup, including tear film break-up time (TBUT), Schirmer's test I (STI), corneal and conjunctival staining, ocular surface disease index (OSDI) scoring, and in vivo confocal microscopy (to assess corneal dendritic cell density [cDCD] and subbasal nerve plexus [SBNP] features) was performed in the study subjects. Tear fluid using Schirmer's strip and serum were collected from the subjects. Multiplex ELISA or single analyte ELISA was performed to measure 34 tear-soluble factors levels including vitamin D. Results Significantly higher OSDI discomfort score, lower TBUT, and lower STI were observed in DED patients. cDCD was significantly higher in DED patients. No significant difference was observed in SBNP features. Tear fluid IL-1β, IL-17A, MMP9, MMP10, MMP9/TIMP ratio, and VEGF-B were significantly higher in DED patients. Significantly lower tear fluid IL-2, IP-10, NPY, VEGF-A, and vitamin D was observed in DED patients. These dysregulated tear factors showed significant associations with DED signs and symptoms. Conclusions Altered tear fluid soluble factors with potential to modulate nociception exhibited a distinct association with ocular surface discomfort status, TBUT, STI, and cDCD. This implies a functional relationship between the various tear-soluble factors and dry eye pathogenesis, indicating new molecular targets for designing targeted therapies.

The Common Antidiabetic Drug Metformin Reduces Odds of Developing Age-Related Macular Degeneration

Abstract: Purpose AMD is the leading cause of irreversible blindness in older individuals in the Western world, and there are currently no therapies to halt disease progression. Studies suggest that the commonly prescribed antidiabetic drug, metformin, is associated with decreased risk of several ocular diseases, but no work has investigated the effect of metformin use on development of AMD. Thus, we aim to investigate whether metformin use is associated with decreased risk of developing AMD. Methods In this retrospective case-control study, we used medical records from patients older than 55 who have visited a University of Florida health clinic. Three controls were matched for every AMD case, defined by International Classification of Diseases, Ninth Revision code, based on the Charlson Comorbidity Index to ensure comparable baseline overall health status. Univariate and conditional multivariable logistic regressions were used to determine the association between a variety of covariates, including metformin use, and AMD diagnosis. Results Metformin use was associated with decreased odds of developing AMD, independently of the other covariates investigated, with an odds ratio of 0.58 and a 95% confidence interval of 0.43 to 0.79. Other medications assessed were not associated with decreased odds of developing AMD. Conclusions Patients who had taken metformin had decreased odds of developing AMD, suggesting that metformin may have a therapeutic role in AMD development or progression in those who are at risk. Further work should include clinical trials to investigate prospectively whether metformin has a protective effect in those at risk for developing AMD.

Hyperlipidemia, Blood Lipid Level, and the Risk of Glaucoma: A Meta-Analysis

Abstract: Purpose Previous studies reported that hyperlipidemia and blood lipid levels were associated with glaucoma, ocular hypertension (OHT), and intraocular pressure (IOP). However, studies aimed at investigating this association have yielded conflicting results. Therefore, to shed light on these inconclusive findings, we performed multiple distinct meta-analyses to clarify the association of hyperlipidemia and blood lipid levels with glaucoma, OHT, and IOP. Methods A systematic literature search from Embase, Web of Science, and PubMed was performed to identify relevant studies. To assess the association between hyperlipidemia and glaucoma, we used the pooled odds ratio (OR) with 95% confidence interval (CI). When we assessed the association between blood lipid levels and IOP levels, the pooled mean difference in IOP associated with a 10 mg/dL increase in the blood lipid level was estimated. The pooled difference in IOP was also estimated between patients with and without hyperlipidemia. All the papers that assessed the correlation between hyperlipidemia and glaucoma, between blood lipid levels and IOP levels, and between hyperlipidemia and IOP were included in this meta-analysis. Results We detected a marked association between hyperlipidemia and glaucoma (OR = 1.37; 95% CI = 1.16-1.61), with significant heterogeneity among studies. However, hyperlipidemia was not significantly associated with glaucoma in our analysis of only cross-sectional studies, studies that reported only on hypercholesterolemia patients, studies that were conducted only in North America and Europe, or studies in which normal-tension glaucoma (NTG) patients were included only in the subgroup analyses. The pooled results showed that an increase of 10 mg/dL in blood triglyceride levels would increase the IOP by 0.016 mm Hg (95% CI = 0.009-0.024), with evident heterogeneity between studies (P < 0.001; I2 = 92.0%). The pooled results showed that the blood total cholesterol and low-density lipoprotein-cholesterol (LDL-c) level both had a significant association with IOP. When compared to the patients with nonhyperlipidemia, those with hyperlipidemia had a significantly higher IOP of 0.51 mm Hg (95% CI = 0.18-0.83) (P = 0.001 for heterogeneity; I2 = 81.6%). Conclusions The evidence suggests that hyperlipidemia is significantly associated with an increased risk of glaucoma and that hyperlipidemia and the increased blood lipid levels are associated with increased IOP.

The Retina in Alzheimer's Disease: Histomorphometric Analysis of an Ophthalmologic Biomarker.

Abstract: Purpose To provide a histopathologic, morphometric analysis of the retina in Alzheimer's disease (AD). Methods Human postmortem retinas from eight patients with AD (mean age: 80 ± 12.7 years) and from 11 age-matched controls (mean age: 78 ± 16.57 years) were analyzed. The retinas were sampled from the superior quadrant on both the temporal and nasal sides with respect to the optic nerve. Thickness of the inner and outer layers involving the retinal nerve fiber layer (RNFL), retinal ganglion cell layer (RGCL), inner plexiform layer (IPL), inner nuclear layer (INL), and outer nuclear layer (ONL) were measured and compared between controls and AD. A total of 16 measurements of retinal thickness were acquired for each layer. Results RNFL thinning supero-temporally was significant closest to the optic nerve (∼35% thickness reduction; P < 0.001). Supero-nasally, RNFL was thinner throughout all points (∼40% reduction; P < 0.001). Supero-temporally, RGCL thinning was pronounced toward the macula (∼35% thickness reduction; P < 0.001). Supero-nasally, RGCL showed uniform thinning throughout (∼35% reduction; P < 0.001). IPL thinning supero-temporally was statistically significant in the macula (∼15% reduction; P < 0.01). Supero-nasal IPL featured uniform thinning throughout (∼25% reduction; P < 0.001). Supero-temporally, INL and ONL thinning were pronounced toward the macula (∼25% reduction; P < 0.01). Supero-nasally, INL and ONL were thinner throughout (∼25% reduction; P < 0.01). Conclusions Our study revealed marked thinning in both the inner and outer layers of the retina. These quantified histopathologic findings provide a more comprehensive understanding of the retina in AD than previously reported.

Identification of Candidate miRNA Biomarkers for Glaucoma

Abstract: Purpose Glaucoma, a leading cause of blindness worldwide, often remains undetected until irreversible vision loss has occurred. Treatments focus on lowering intraocular pressure (IOP), the only modifiable and readily measurable risk factor. However, IOP can vary and does not always predict disease progression. MicroRNAs (miRNAs) are promising biomarkers. They are abundant and stable in biological fluids, including plasma and aqueous humor (AqH). We aimed to identify differentially expressed miRNAs in AqH and plasma from glaucoma, exfoliation syndrome (XFS), and control subjects. Methods Plasma and AqH from two ethnic cohorts were harvested from glaucoma or XFS (often associated with glaucoma, n = 33) and control (n = 31) patients undergoing elective surgery. A custom miRNA array measured 372 miRNAs. Molecular target prediction and pathway analysis were performed with Ingenuity Pathway Analysis (IPA) and DIANA bioinformatical tools. Results Levels of miRNAs in plasma, a readily accessible biomarker source, correlated with miRNA levels in AqH. Twenty circulating miRNAs were at least 1.5-fold higher in glaucoma or XFS patients than in controls across two ethnic cohorts: miR-4667-5p (P = 4.1 × 10-5), miR-99b-3p (P = 4.8 × 10-5), miR-637 (P = 5.1 × 10-5), miR-4490 (P = 5.7 × 10-5), miR-1253 (P = 6.0 × 10-5), miR-3190-3p (P = 3.1 × 10-4), miR-3173-3p (P = 0.001), miR-608 (P = 0.001), miR-4725-3p (P = 0.002), miR-4448 (P = 0.002), and miR-323b-5p (P = 0.002), miR-4538 (P = 0.003), miR-3913-3p (P = 0.003), miR-3159 (P = 0.003), miR-4663 (P = 0.003), miR-4767 (P = 0.003), miR-4724-5p (P = 0.003), miR-1306-5p (P = 0.003), miR-181b-3p (P = 0.004), and miR-433-3p (P = 0.004). miR-637, miR-1306-5p, and miR-3159, in combination, allowed discrimination between glaucoma patients and control subjects (AUC = 0.91 ± 0.008, sensitivity 85.0%, specificity 87.5%). Conclusions These results identify specific miRNAs as potential biomarkers and provide insight into the molecular processes underlying glaucoma.

Arginine and Carnitine Metabolites Are Altered in Diabetic Retinopathy.

Abstract: Purpose To determine plasma metabolite and metabolic pathway differences between patients with type 2 diabetes with diabetic retinopathy (DR) and without retinopathy (diabetic controls), and between patients with proliferative DR (PDR) and nonproliferative DR (NPDR). Methods Using high-resolution mass spectrometry with liquid chromatography, untargeted metabolomics was performed on plasma samples from 83 DR patients and 90 diabetic controls. Discriminatory metabolic features were identified through partial least squares discriminant analysis, and linear regression was used to adjust for age, sex, diabetes duration, and hemoglobin A1c. Pathway analysis was performed using Mummichog 2.0. Results In the adjusted analysis, 126 metabolic features differed significantly between DR patients and diabetic controls. Pathway analysis revealed alterations in the metabolism of amino acids, leukotrienes, niacin, pyrimidine, and purine. Arginine, citrulline, glutamic γ-semialdehyde, and dehydroxycarnitine were key contributors to these pathway differences. A total of 151 features distinguished PDR patients from NPDR patients, and pathway analysis revealed alterations in the β-oxidation of saturated fatty acids, fatty acid metabolism, and vitamin D3 metabolism. Carnitine was a major contributor to the pathway differences. Conclusions This study demonstrates that arginine and citrulline-related pathways are dysregulated in DR, and fatty acid metabolism is altered in PDR patients compared with NPDR patients.

Nicotinamide Deficiency in Primary Open-Angle Glaucoma.

Abstract: Purpose To investigate the plasma concentration of nicotinamide in primary open-angle glaucoma (POAG). Methods Plasma of 34 POAG individuals was compared to that of 30 age- and sex-matched controls using a semiquantitative method based on liquid chromatography coupled to high-resolution mass spectrometry. Subsequently, an independent quantitative method, based on liquid chromatography coupled to mass spectrometry, was used to assess nicotinamide concentration in the plasma from the same initial cohort and from a replicative cohort of 20 POAG individuals and 15 controls. Results Using the semiquantitative method, the plasma nicotinamide concentration was significantly lower in the initial cohort of POAG individuals compared to controls and further confirmed in the same cohort, using the targeted quantitative method, with mean concentrations of 0.14 μM (median: 0.12 μM; range, 0.06-0.28 μM) in the POAG group (-30%; P = 0.022) and 0.19 μM (median: 0.18 μM; range, 0.08-0.47 μM) in the control group. The quantitative dosage also disclosed a significantly lower plasma nicotinamide concentration (-33%; P = 0.011) in the replicative cohort with mean concentrations of 0.14 μM (median: 0.14 μM; range, 0.09-0.25 μM) in the POAG group, and 0.19 μM (median: 0.21 μM; range, 0.09-0.26 μM) in the control group. Conclusions Glaucoma is associated with lower plasmatic nicotinamide levels, compared to controls, suggesting that nicotinamide supplementation might become a future therapeutic strategy. Further studies are needed, in larger cohorts, to confirm these preliminary findings.

The Human Ocular Surface Fungal Microbiome.

Abstract: Purpose To enumerate the ocular surface fungal microbiome of healthy human eyes by using next-generation sequencing (NGS). Methods Tarsal and fornix conjunctiva from the lower and upper lids of both eyes of healthy individuals were swabbed in duplicate separately. A total of 34 samples were collected from both the eyes of 17 individuals, which were used for the generation of ocular surface fungal microbiomes by NGS. Twenty-four swabs were used for the detection of culturable fungi by the conventional cultivable method. Microbiome generation involved DNA extraction, internal transcribed spacer 2 (ITS2) amplification, library preparation, amplicon sequencing, taxonomic assignment of sequences, diversity analyses, and identification of genera. Results The cultivable method detected fungi in 3 out of 24 (12.5 %) ocular surface swabs, whereas NGS identified fungi in 25 of the 34 (73.5 %) swabs. In the cultivable method Aspergillus was the only genus detected, whereas NGS detected 65 distinct genera with 12 to 24 genera per microbiome. Genera Aspergillus, Setosphaeria, Malassezia, and Haematonectria were present in the 25 eyes in which fungi were detected. Alpha diversity in the two eyes was similar and sex had no effect, but Chao1 and Simpson indices were altered by age. Conclusions This study explored the ocular surface fungal microbiome of healthy individuals using NGS and identified a greater degree of diversity of fungi than with the conventional cultivable method. It was observed that several fungal genera were associated with the healthy conjunctiva.