Pathophysiology of age-related macular degeneration

Integrating explainable machine learning and transcriptomics data reveals cell-type specific immune signatures underlying macular degeneration

Genome-wide association studies (GWAS) have established key role of immune dysfunction in Age-related Macular Degeneration (AMD), though the precise role of immune cells remains unclear. Here, we develop an explainable machine-learning pipeline (ML) using transcriptome data of 453 donor retinas, identifying 81 genes distinguishing AMD from controls (AUC-ROC of 0.80, CI 0.70-0.92). Most of these genes were enriched in their expression within retinal glial cells, particularly microglia and astrocytes. Their role in AMD was further strengthened by cellular deconvolution, which identified distinct differences in microglia and astrocytes between normal and AMD. We corroborated these findings using independent single-cell data, where several ML genes exhibited differential expression. Finally, the integration of AMD-GWAS data identified a regulatory variant, rs4133124 at PLCG2, as a novel AMD association. Collectively, our study provides molecular insights into the recurring theme of immune dysfunction in AMD and highlights the significance of glial cell differences in AMD progression.

Progress of ADAM17 in Fibrosis-Related Diseases

Fibrosis leads to structural damage and functional decline and is characterized by an accumulation of fibrous connective tissue and a reduction in parenchymal cells. Because of its extremely poor prognosis, organ fibrosis poses a significant economic burden. In order to prevent and treat fibrosis more effectively, potential mechanisms need to be investigated. A disintegrin and metalloprotease 17 (ADAM17) is a membrane-bound protein. It regulates intracellular signaling and membrane protein degradation. Fibrosis mediated by ADAM17 has been identified as an important contributor, although the specific relationship between its multiple regulatory functions and the pathogenesis is unclear. This article describes ADAM17 activation, function, and regulation, as well as the role of ADAM17 mediated fibrosis injury in kidney, liver, heart, lung, skin, endometrium, and retina. To develop new therapeutic approaches based on ADAM17 related signal pathways.

The impact of NF-κB on inflammatory and angiogenic processes in age-related macular degeneration

Age-related macular degeneration (AMD) is a prominent cause of vision loss, characterized by two different types, dry (atrophic) and wet (neovascular). Dry AMD is distinguished by the progressive deterioration of retinal cells, which ultimately causes a decline in vision. In contrast, wet AMD is defined by the abnormal development of blood vessels underneath the retina, leading to a sudden and severe vision impairment. The course of AMD is primarily driven by chronic inflammation and pathological angiogenesis, in which the NF-κB signaling pathway plays a crucial role. The activation of NF-κB results in the generation of pro-inflammatory cytokines, chemokines, and angiogenic factors like VEGF, which contribute to inflammation and the formation of new blood vessels in AMD. This review analyzes the intricate relationship between NF-κB signaling, inflammation, and angiogenesis in AMD and assesses the possibility of using NF-κB as a target for therapy. The evaluation involves a comprehensive examination of preclinical and clinical evidence that substantiates the effectiveness of NF-κB inhibitors in treating AMD by diminishing inflammation and pathological angiogenesis.

Leading edge of the a-wave of the electroretinogram and sodium iodate-induced age-related macular degeneration: A model

BACKGROUND

Iron-induced oxidative stress was thought to be the reason why the a-wave amplitude of the electroretinogram (ERG) dropped when iron ions were present. It is assumed that reactive oxygen species (ROS) are generated in the presence of iron ions, and this leads to a decrease in hyperpolarization of the photoreceptor. It is known that in age-related macular degeneration (AMD), sodium iodate can induce oxidative stress, apoptosis, and retinal damage, which mimic the effects of clinical AMD. Here, the reduction of the a-wave amplitude in mice with sodium iodate-induced age-related macular degeneration is explained.

METHODS

The leading edge of the a-wave is divided into voltages developed by cones and rods. The same oxidative stress model is applied here since sodium iodate causes the creation of ROS in a manner similar to that caused by iron ions, with the exception that the retina is treated as a circuit of various resistances when computing the photoresponse. Moreover, sodium iodate also leads to apoptosis and, hence, may cause misalignment in cones (not in rods) during the initial stage of apoptosis in AMD. To include the effects of apoptosis and shortening in cones and rods, we have used a factor representing the fraction of total cones and rods that are alive. To include the effect of misalignment of cones on the reduction of the a-wave amplitude, we have used the Stiles-Crawford function to calculate the number of photoisomerizations occurring in a photoreceptor misaligned at an angle θ. The results are compared with experimental data.

RESULTS

In sodium iodate-treated eyes, the ROS produced can attract calcium ions in the photoreceptor, which increases the calcium influx. In the case of the cones, the inclusion of the misalignment angle in the phototransduction process helps in determining the voltage and slope of the voltage vs. time graph.The smaller the fraction of active photoreceptors, the smaller the amplitude of the a-wave. The calcium influx, misaligned photoreceptors, and total photoreceptor loss all cause the amplitude of the a-wave to decrease, and at any time from the beginning of phototransduction cascade, the calcium influx causes the slope of the a-wave to increase.

CONCLUSION

The reduction in the a-wave amplitude in the eyes of sodium iodate-treated mice is attributed to oxidative stress in both cones and rods and cone misalignment, which ultimately lead to apoptosis and vision loss in AMD.

Inhibition of oxidative stress-induced epithelial-mesenchymal transition in retinal pigment epithelial cells of age-related macular degeneration model by suppressing ERK activation

INTRODUCTION

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is related to the pathogenesis of various retinopathies including age-related macular degeneration (AMD). Oxidative stress is the major factor that induces degeneration of RPE cells associated with the etiology of AMD.

OBJECTIVES

Sodium iodate (NaIO3) generates intracellular reactive oxygen species (ROS) and is widely used to establish a model of AMD due to the selective induction of retinal degeneration. This study was performed to clarify the effects of multiple NaIO3-stimulated signaling pathways on EMT in RPE cells.

METHODS

The EMT characteristics in NaIO3-treated human ARPE-19 cells and RPE cells of the mouse eyes were analyzed. Multiple oxidative stress-induced modulators were investigated and the effects of pre-treatment with Ca2+ chelator, extracellular signal-related kinase (ERK) inhibitor, or epidermal growth factor receptor (EGFR) inhibitor on NaIO3-induced EMT were determined. The efficacy of post-treatment with ERK inhibitor on the regulation of NaIO3-induced signaling pathways was dissected and its role in retinal thickness and morphology was evaluated by using histological cross-sections and spectral domain optical coherence tomography.

RESULTS

We found that NaIO3 induced EMT in ARPE-19 cells and in RPE cells of the mouse eyes. The intracellular ROS, Ca2+, endoplasmic reticulum (ER) stress marker, phospho-ERK, and phospho-EGFR were increased in NaIO3-stimulated cells. Our results showed that pre-treatment with Ca2+ chelator, ERK inhibitor, or EGFR inhibitor decreased NaIO3-induced EMT, interestingly, the inhibition of ERK displayed the most prominent effect. Furthermore, post-treatment with FR180204, a specific ERK inhibitor, reduced intracellular ROS and Ca2+ levels, downregulated phospho-EGFR and ER stress marker, attenuated EMT of RPE cells, and prevented structural disorder of the retina induced by NaIO3.

CONCLUSIONS

ERK is a crucial regulator of multiple NaIO3-induced signaling pathways that coordinate EMT program in RPE cells. Inhibition of ERK may be a potential therapeutic strategy for the treatment of AMD.

Pluripotent stem cell-derived models of retinal disease: Elucidating pathogenesis, evaluating novel treatments, and estimating toxicity

Blindness poses a growing global challenge, with approximately 26% of cases attributed to degenerative retinal diseases. While gene therapy, optogenetic tools, photosensitive switches, and retinal prostheses offer hope for vision restoration, these high-cost therapies will benefit few patients. Understanding retinal diseases is therefore key to advance effective treatments, requiring in vitro models replicating pathology and allowing quantitative assessments for drug discovery. Pluripotent stem cells (PSCs) provide a unique solution given their limitless supply and ability to differentiate into light-responsive retinal tissues encompassing all cell types. This review focuses on the history and current state of photoreceptor and retinal pigment epithelium (RPE) cell generation from PSCs. We explore the applications of this technology in disease modelling, experimental therapy testing, biomarker identification, and toxicity studies. We consider challenges in scalability, standardisation, and reproducibility, and stress the importance of incorporating vasculature and immune cells into retinal organoids. We advocate for high-throughput automation in data acquisition and analyses and underscore the value of advanced micro-physiological systems that fully capture the interactions between the neural retina, RPE, and choriocapillaris.

Retinal Pigment Epithelium Pigment Granules: Norms, Age Relations and Pathology

The retinal pigment epithelium (RPE), which ensures the normal functioning of the neural retina, is a pigmented single-cell layer that separates the retina from the Bruch's membrane and the choroid. There are three main types of pigment granules in the RPE cells of the human eye: lipofuscin granules (LG) containing the fluorescent "age pigment" lipofuscin, melanoprotein granules (melanosomes, melanolysosomes) containing the screening pigment melanin and complex melanolipofuscin granules (MLG) containing both types of pigments simultaneously-melanin and lipofuscin. This review examines the functional role of pigment granules in the aging process and in the development of oxidative stress and associated pathologies in RPE cells. The focus is on the process of light-induced oxidative degradation of pigment granules caused by reactive oxygen species. The reasons leading to increased oxidative stress in RPE cells as a result of the oxidative degradation of pigment granules are considered. A mechanism is proposed to explain the phenomenon of age-related decline in melanin content in RPE cells. The essence of the mechanism is that when the lipofuscin part of the melanolipofuscin granule is exposed to light, reactive oxygen species are formed, which destroy the melanin part. As more melanolipofuscin granules are formed with age and the development of degenerative diseases, the melanin in pigmented epithelial cells ultimately disappears.

Hyperpigmentary abnormalities in age-related macular degeneration: association with progression and impact on visual sensitivity

BACKGROUND/AIMS

To investigate the additional prognostic value of quantifying the extent of colour fundus photography (CFP)-defined hyperpigmentary abnormalities (HPAs) compared with their presence alone for predicting progression to late-stage age-related macular degeneration (AMD) and to understand their association with visual sensitivity in individuals with intermediate AMD.

METHODS

140 participants with bilateral large drusen underwent multimodal imaging and microperimetry at baseline and then every 6 months for up to 3 years. Baseline CFPs were graded for the presence of HPAs and their extent was quantified. Optical coherence tomography (OCT) scans were used to quantify drusen volume. Predictive models for progression to late AMD (including OCT signs of atrophy) were developed using either HPA presence or extent. The association between HPA extent with mean visual sensitivity (both overall and sector based) was also evaluated. All models were adjusted for the confounders of baseline age and drusen volume.

RESULTS

The predictive performance for late AMD development was not significantly different for HPA presence or extent (p=0.92). Increasing HPA extent in each sector, but not its overall extent in an eye, was associated with reduced sector-based visual sensitivity (p<0.001 and p=0.671, respectively).

CONCLUSION

In a cohort with bilateral large drusen, quantifying HPA extent did not improve the prediction of late AMD development compared with presence alone. HPA extent was associated with more local, rather than generalised, reductions in visual sensitivity. These findings suggest that quantification of HPA extent adds little to the prediction of AMD progression, but that it provides an imaging biomarker of visual dysfunction.

Indenopyrene and Blue-Light Co-Exposure Impairs the Tightly Controlled Activation of Xenobiotic Metabolism in Retinal Pigment Epithelial Cells: A Mechanism for Synergistic Toxicity

High energy visible (HEV) blue light is an increasing source of concern for visual health. Polycyclic aromatic hydrocarbons (PAH), a group of compounds found in high concentrations in smokers and polluted environments, accumulate in the retinal pigment epithelium (RPE). HEV absorption by indeno [1,2,3-cd]pyrene (IcdP), a common PAH, synergizes their toxicities and promotes degenerative changes in RPE cells comparable to the ones observed in age-related macular degeneration. In this study, we decipher the processes underlying IcdP and HEV synergic toxicity in human RPE cells. We found that IcdP-HEV toxicity is caused by the loss of the tight coupling between the two metabolic phases ensuring IcdP efficient detoxification. Indeed, IcdP/HEV co-exposure induces an overactivation of key actors in phase I metabolism. IcdP/HEV interaction is also associated with a downregulation of proteins involved in phase II. Our data thus indicate that phase II is hindered in response to co-exposure and that it is insufficient to sustain the enhanced phase I induction. This is reflected by an accelerated production of endogenous reactive oxygen species (ROS) and an increased accumulation of IcdP-related bulky DNA damage. Our work raises the prospect that lifestyle and environmental pollution may be significant modulators of HEV toxicity in the retina.

Alteration in Melanin Content in Retinal Pigment Epithelial Cells upon Hydroquinone Exposure

Abnormal pigmentation or depigmentation of the retinal pigment epithelium (RPE) is a precursor to neovascular age-related macular degeneration (nAMD). In this study, we evaluated the effects of hydroquinone (HQ), the most potent reductant in cigarette smoke, on the melanin production in RPE cells. Induced pluripotent stem cell (iPS)-derived RPE and adult retinal pigment epithelial (ARPE-19) cells were cultured with HQ. Real-time reverse transcription polymerase chain reaction revealed that the expression of melanin-related genes decreased due to the addition of HQ for 1 day. Enzyme-linked immunosorbent immunoassay showed that the concentration of melanin significantly decreased due to the addition of HQ for 24 h. A suspension of RPE cells with HQ for 24 h was prepared, and the absorbance was measured. The absorbance decreased particularly under blue light, suggesting that blue light may reach the choroid and cause choroidal inflammation. Additionally, melanin levels significantly decreased due to the addition of HQ for 1 week. After blue light irradiation on the RPE with HQ for 1 week, the vascular endothelial growth factor in the medium was significantly higher in the HQ group than in the control group. HQ-induced changes in melanin production may be responsible for the uneven pigmentation of the RPE, and these changes may cause nAMD.

Evaluation of Local Retinal Function in Light-Damaged Rats Using Multifocal Electroretinograms and Multifocal Visual Evoked Potentials

Electroretinograms (ERGs) are often used to evaluate retinal function. However, assessing local retinal function can be challenging; therefore, photopic and scotopic ERGs are used to record whole-retinal function. This study evaluated focal retinal function in rats exposed to continuous light using a multifocal ERG (mfERG) system. The rats were exposed to 1000 lux of fluorescent light for 24 h to induce photoreceptor degeneration. After light exposure, the rats were reared under cyclic light conditions (12 h: 5 lux, 12 h: dark). Photopic and multifocal ERGs and single-flash and multifocal visual evoked potentials (mfVEPs) were recorded 7 days after light exposure. Fourteen days following light exposure, paraffin-embedded sections were prepared from the eyes for histological evaluation. The ERG and VEP responses dramatically decreased after 24 h of light exposure, and retinal area-dependent decreases were observed in mfERGs and mfVEPs. Histological assessment revealed severe damage to the superior retina and less damage to the inferior retina. Considering the recorded visual angles of mfERGs and mfVEPs, the degenerated area shown on the histological examinations correlates well with the responses from multifocal recordings.

Correlations between subfoveal choroidal thickness, macular thickness, and visual outcome in neovascular age-related macular degeneration using swept source OCT: insights from intravitreal aflibercept treatment

BACKGROUND

Age-related macular degeneration (AMD) is a leading cause of visual impairment among individuals aged 50 and above, often resulting in irreversible vision loss (1). Currently, antiangiogenic therapy is the primary treatment approach for neovascular AMD (2). The choroid has gained significant attention in recent years due to its involvement in various ocular pathologies (7). The objective of this study was to evaluate visual acuity and correlate pre-treatment variables, such as foveal thickness and choroidal thickness, with post-treatment outcomes.

MATERIALS AND METHODS

This study was designed as a prospective interventional study to investigate the changes in choroidal and macular thickness in patients with neovascular AMD who received intravitreal aflibercept injections. The study utilized medical records and employed Swept Source Optical Coherence Tomography (OCT-SS) for evaluation. The data was collected from patients treated in Presidente Prudente, Brazil, during a three-month load dose period.

RESULTS

The best-corrected mean visual acuity significantly improved from 1.0 logarithm of the minimum resolution angle (logMAR) units to 0.55 logMAR after treatment with aflibercept (p < 0.001). Patients undergoing treatment exhibited a significant decrease in average macular thickness from 323 μm to 232 μm (p = 0.001), as well as a reduction in choroidal thickness from 206 μm to 172 μm (p = 0.031), while maintaining intraocular pressure within the normal range (p = 0.719) without significant variation. Statistically significant associations were found between the difference in pre- and post-treatment choroidal thickness and the pretreatment values of macular thickness (p = 0.005) and choroidal thickness (p = 0.013). There was also a statistically significant correlation between the difference in pre- and post-treatment macular thickness and the pretreatment macular thickness value (p < 0.001).

CONCLUSION

In this study, aflibercept exhibited remarkable effectiveness in reducing macular and choroidal thickness, as evaluated using OCT-SS, and significantly improved visual acuity in patients with neovascular AMD. The assessment of both choroidal and macular changes, as well as their correlations, can provide valuable insights for clinicians, enabling them to make well-informed therapeutic decisions and effectively monitor treatment outcomes. Notably, this study contributes to the existing body of literature as the first to establish a correlation between pretreatment foveal thickness, variation in choroidal thickness, and post-treatment choroidal thickness.

The risk of retinal vein occlusion among patients with neovascular age related macular degeneration: a large-scale cohort study

PURPOSE

To examine the risk for retinal-vein-occlusion (RVO) in patients with neovascular age-related-macular-degeneration (AMD) as compared to age- and sex-matched controls.

METHOD

This is a population-based, cohort study. The study encompassed 24,578 consecutive patients with neovascular AMD and 66,129 control subjects. Multivariate cox regression analysis was utilized to detect the risk of RVO among patients with neovascular AMD. Predictors of RVO in patients with neovascular AMD were identified using multivariate logistic regression analysis. Mortality of patients was assessed using Kaplan-Meier method.

RESULTS

The incidence rate of RVO was estimated at 1.25 (95% CI, 1.06-1.45) per 1000 person-years among patients with neovascular AMD and 0.25 (95% CI, 0.20-0.31) per 1000 person-years among controls. Patients with neovascular AMD were associated with an increased risk of RVO (adjusted HR, 4.35; 95% CI, 3.34-5.66; P < 0.001). Among patients with neovascular AMD, older age (≥79.0 years) was associated with a decreased risk of RVO (adjusted OR, 0.50; 95% CI, 0.37-0.70; P < 0.001), whilst a history of glaucoma increased the likelihood of RVO (adjusted OR, 2.66; 95% CI, 1.94-3.65; P < 0.001). Patients with neovascular AMD and comorbid RVO had a comparable risk of all-cause mortality relative to other patients with neovascular AMD (HR, 0.90; 95% CI, 0.67-1.22; P = 0.500) CONCLUSIONS: An increased risk of RVO was found among patients with neovascular AMD. Younger age and glaucoma predicted the development of RVO in patients with neovascular AMD. Awareness of this comorbidity is of benefit for clinicians as patients with neovascular AMD might be carefully examined for RVO signs and complications.

Quantitative Autofluorescence in Non-Neovascular Age Related Macular Degeneration

Quantitative autofluorescence (qAF8) level is a presumed surrogate marker of lipofuscin content in the retina. We investigated the changes in the qAF8 levels in non-neovascular AMD. In this prospective cohort study, Caucasians aged ≥50 years with varying severity of non-neovascular AMD in at least one eye and Snellen visual acuity ≥6/18 were recruited. The qAF8 levels were analysed in the middle eight segments of the Delori pattern (HEYEX software, Heidelberg, Germany). The AMD categories were graded using both the Beckman classification and multimodal imaging (MMI) to include the presence of subretinal drusenoid deposits (SDD). A total of 353 eyes from 231 participants were analyzed. Compared with the age-matched controls, the qAF8 values decreased in the eyes with AMD (adjusted % difference = -19.7% [95% CI -28.8%, -10.4%]; p < 0.001) and across the AMD categories, (adjusted % differences; Early, -13.1% (-24.4%, -1%), p = 0.04; intermediate AMD (iAMD), -22.9% (-32.3%, -13.1%), p < 0.001; geographic atrophy -25.2% (-38.1%, -10.4%), p = 0.002). On MMI, the qAF8 was reduced in the AMD subgroups relative to the controls, (adjusted % differences; Early, -5.8% (-18.9%, 8.3%); p = 0.40; iAMD, -26.7% (-36.2%, -15.6%); p < 0.001; SDD, -23.7% (-33.6%, -12.2%); p < 0.001; atrophy, -26.7% (-39.3%, -11.3%), p = 0.001). The qAF8 levels declined early in AMD and were not significantly different between the severity levels of non-neovascular AMD, suggesting the early and sustained loss of function of the retinal pigment epithelium in AMD.

Role of Oxidative Stress in Ocular Diseases: A Balancing Act

Redox homeostasis is a delicate balancing act of maintaining appropriate levels of antioxidant defense mechanisms and reactive oxidizing oxygen and nitrogen species. Any disruption of this balance leads to oxidative stress, which is a key pathogenic factor in several ocular diseases. In this review, we present the current evidence for oxidative stress and mitochondrial dysfunction in conditions affecting both the anterior segment (e.g., dry eye disease, keratoconus, cataract) and posterior segment (age-related macular degeneration, proliferative vitreoretinopathy, diabetic retinopathy, glaucoma) of the human eye. We posit that further development of therapeutic interventions to promote pro-regenerative responses and maintenance of the redox balance may delay or prevent the progression of these major ocular pathologies. Continued efforts in this field will not only yield a better understanding of the molecular mechanisms underlying the pathogenesis of ocular diseases but also enable the identification of novel druggable redox targets and antioxidant therapies.

Measure of Visual Function

This chapter describes various methods of the assessment of visual function used for assessing disease progression and treatment response in patients with retinitis pigmentosa (RP). These methods include full-field stimulus testing (FST), near-infrared autofluorescence (NIR-AF), quantitative fundus autofluorescence (qAF), and quantitative near-infrared autofluorescence (qNIR-AF). This chapter will also outline the protocol for adaptive optics (AO) imaging of RP patients and cover how each of these methods is used for RP patients, with details including the expected findings, as evidenced by recent literature.

Effects of radiation exposure on brain health: a state of the art and new challenges

Good brain health refers to a condition in which a person may fully realize their talents and improve their psychological, emotional, cognitive, and behavioral functioning to cope with life's challenges. Various causes of CNS diseases are now being investigated. Radiation is one of the factors that affects the brain and causes a variety of problems. The emission or transmission of energy in the form of waves or particles via space or a material medium is known as radiation. Particle beams and electromagnetic waves are two types of ionizing radiation that have the potential to ionize atoms in a material (separating them into positively charged ions and negatively charged electrons). Radiation to the CNS can induce delayed puberty, which can lead to hyperprolactinemia, and the hypothalamic-pituitary axis can lead to gonadotropin deficit if the hypothalamic-pituitary axis is involved in the radiation field. Ionizing radiation is the most common kind of radiation. Here, we focus on the different effects of radiation on brain health. In this article, we will look at a variety of CNS diseases and how radiation affects each one, as well as how it affects the brain's numerous processes.

Exploring the pathogenesis of age-related macular degeneration: A review of the interplay between retinal pigment epithelium dysfunction and the innate immune system

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss in the older population. Classical hallmarks of early and intermediate AMD are accumulation of drusen, a waste deposit formed under the retina, and pigmentary abnormalities in the retinal pigment epithelium (RPE). When the disease progresses into late AMD, vision is affected due to death of the RPE and the light-sensitive photoreceptors. The RPE is essential to the health of the retina as it forms the outer blood retinal barrier, which establishes ocular immune regulation, and provides support for the photoreceptors. Due to its unique anatomical position, the RPE can communicate with the retinal environment and the systemic immune environment. In AMD, RPE dysfunction and the accumulation of drusen drive the infiltration of retinal and systemic innate immune cells into the outer retina. While recruited endogenous or systemic mononuclear phagocytes (MPs) contribute to the removal of noxious debris, the accumulation of MPs can also result in chronic inflammation and contribute to AMD progression. In addition, direct communication and indirect molecular signaling between MPs and the RPE may promote RPE cell death, choroidal neovascularization and fibrotic scarring that occur in late AMD. In this review, we explore how the RPE and innate immune cells maintain retinal homeostasis, and detail how RPE dysfunction and aberrant immune cell recruitment contribute to AMD pathogenesis. Evidence from AMD patients will be discussed in conjunction with data from preclinical models, to shed light on future therapeutic targets for the treatment of AMD.

Microbiota mitochondria disorders as hubs for early age-related macular degeneration

Age-related macular degeneration (AMD) is a progressive neurodegenerative disease affecting the central area (macula lutea) of the retina. Research on the pathogenic mechanism of AMD showed complex cellular contribution governed by such risk factors as aging, genetic predisposition, diet, and lifestyle. Recent studies suggested that microbiota is a transducer and a modifier of risk factors for neurodegenerative diseases, and mitochondria may be one of the intracellular targets of microbial signaling molecules. This review explores studies supporting a new concept on the contribution of microbiota-mitochondria disorders to AMD. We discuss metabolic, vascular, immune, and neuronal mechanism in AMD as well as key alterations of photoreceptor cells, retinal pigment epithelium (RPE), Bruch's membrane, choriocapillaris endothelial, immune, and neuronal cells. Special attention was paid to alterations of mitochondria contact sites (MCSs), an organelle network of mitochondria, endoplasmic reticulum, lipid droplets (LDs), and peroxisomes being documented based on our own electron microscopic findings from surgically removed human eyes. Morphometry of Bruch's membrane lipids and proteoglycans has also been performed in early AMD and aged controls. Microbial metabolites (short-chain fatty acids, polyphenols, and secondary bile acids) and microbial compounds (lipopolysaccharide, peptidoglycan, and bacterial DNA)-now called postbiotics-in addition to local effects on resident microbiota and mucous membrane, regulate systemic metabolic, vascular, immune, and neuronal mechanisms in normal conditions and in various common diseases. We also discuss their antioxidant, anti-inflammatory, and metabolic effects as well as experimental and clinical observations on regulating the main processes of photoreceptor renewal, mitophagy, and autophagy in early AMD. These findings support an emerging concept that microbiota-mitochondria disorders may be a crucial pathogenic mechanism of early AMD; and similarly, to other age-related neurodegenerative diseases, new treatment approaches should be targeted at these disorders.

SIG-1451, a Novel, Non-Steroidal Anti-Inflammatory Compound, Attenuates Light-Induced Photoreceptor Degeneration by Affecting the Inflammatory Process

Age-related macular degeneration is a progressive retinal disease that is associated with factors such as oxidative stress and inflammation. In this study, we evaluated the protective effects of SIG-1451, a non-steroidal anti-inflammatory compound developed for treating atopic dermatitis and known to inhibit Toll-like receptor 4, in light-induced photoreceptor degeneration. SIG-1451 was intraperitoneally injected into rats once per day before exposure to 1000 lx light for 24 h; one day later, optical coherence tomography showed a decrease in retinal thickness, and electroretinogram (ERG) amplitude was also found to have decreased 3 d after light exposure. Moreover, SIG-1451 partially protected against this decrease in retinal thickness and increase in ERG amplitude. One day after light exposure, upregulation of inflammatory response-related genes was observed, and SIG-1451 was found to inhibit this upregulation. Iba-1, a microglial marker, was suppressed in SIG-1451-injected rats. To investigate the molecular mechanism underlying these effects, we used lipopolysaccharide (LPS)-stimulated rat immortalised Müller cells. The upregulation of C-C motif chemokine 2 by LPS stimulation was significantly inhibited by SIG-1451 treatment, and Western blot analysis revealed a decrease in phosphorylated I-κB levels. These results indicate that SIG-1451 indirectly protects photoreceptor cells by attenuating light damage progression, by affecting the inflammatory responses.

Potential participation of CTRP6, a complement regulator, in the pathology of age related macular degeneration

PURPOSE

To investigate the localized expression of C1q/tumor necrosis factor related protein (CTRP) 6 in human age-related macular degeneration (AMD) retinal tissues.

EXPERIMENTAL STUDY DESIGN

4 AMD and 3 non-AMD whole eyes of Caucasian donors were used. Eyecups were excised at Eye Bank CorneaGen, Inc.

METHODS

To elucidate the effects of CTRP6, C3b was measured by an enzyme-linked immunosorbent-like assay. CFB versus CTRP6 competitive binding assay was applied to clarify the inhibition by CTRP6 of C3bBb complex formation. The cornea, iris, lens, and vitreous were removed and the eyes were cut into a posterior eye-cup including the retina, choroid, and sclera. Six-µm-thick serial sections of frozen samples underwent hematoxylin-eosin (HE) staining and indirect immunohistochemical staining using primary antibodies, anti-CTRP6, -CTRP5, -CTRP10, -Complement factor H (CFH) and -Clusterin (CLU). Results The two in vitro studies confirmed that CTRP6 has an inhibitory effect on alternative pathways of complement (APC) function and that the molecular target of CTRP6 is the inhibition of the formation of C3bBb. Localized expression for CTRP6 and CFH was found in the drusen of the AMD eyes, both associated with APC inhibition, CLU associated with membrane-attack complex (MAC) inhibition, and CTRP5 associated with retinal degeneration.

CONCLUSION

The localized expression of CTRP6 in the drusen of AMD eyes may open a new insight into the possible involvement of APC regulatory factors in the pathogenesis of AMD, together with the known CFH so far analyzed solely as an APC inhibitor.

Methodological Approach to Improve Surgical Outcomes of a Pig Subretinal Implantation Model

Purpose

To improve outcomes for subretinal implantation surgery in pigs.

Methods

Analysis of variables affecting the success of subretinal implantation surgery was performed on videos of 37 surgeries. Ex vivo experiments were conducted to measure intraocular pressure (IOP) and test various prototyped implanters for effectiveness at maintaining IOP.

Results

A video analysis revealed a prolonged sclerotomy open time owing to a combination of uncontrolled bleeding and excessive fluid outflow often resulting in retinal prolapse. Precauterization of the choroid before full-thickness sclerotomy (n = 10) resulted in a reduced incidence of uncontrolled bleeding from 39.1% (9/23) versus 0% (0/10) (P = 0.005) and improved implantation success from 73% to 90%. An ex vivo analysis of the IOP revealed a mean decrease in the IOP from 30.2 ± 3.0 mm Hg to 5.0 ± 2.1 mm Hg after a fully penetrating sclerotomy. To address this situation, we produced a series of plugs that integrated with a custom implant insertion device to seal the sclerotomy during implantation. The use of the plugs was cumbersome, however, and so we opted instead to increase the width of the inserter tip to fill the open sclerotomy. This improved device restored and maintained IOP during implantation (27.1 ± 1.9 mm Hg). Combined with precauterization the improved inserter resulted in 100% successful implantation (n = 4).

Conclusions

For subretinal implantation in pigs, a modified procedure to precauterize the choroid before sclerotomy combined with an instrument that better fills the scleral opening decreases bleeding, hypotony, and open sclerotomy time, improving the success rate.

Translational Relevance

Better management of IOP and bleeding from a sclerotomy will improve implant-based therapies.

Malondialdehyde-Modified Photoreceptor Outer Segments Promote Choroidal Neovascularization in Mice

Purpose

This study aimed to establish a novel choroidal neovascularization (CNV) mouse model through subretinally injecting malondialdehyde (MDA)-modified photoreceptor outer segments (POS), which was more consistent with the pathogenesis of wet age-related macular degeneration (AMD).

Methods

MDA-modified POS were subretinally injected in C57BL/6J mice. Four weeks later, to assess the volume of CNV and the morphology of retinal pigment epithelium (RPE), isolectin B4 and zonula occludens-1 antibody were used for immunostaining. Fundus fluorescent angiography and optical coherence tomography imaging were used to describe the morphologic features of CNV. Transepithelial resistance was measured on polarized ARPE-19 cells. Vascular endothelial growth factor levels in the cell culture medium were detected by enzyme-linked immunosorbent assay. The protein and messenger RNA expression levels of autophagy markers were measured using Western blot and quantitative polymerase chain reaction.

Results

CNV and RPE atrophy were successfully induced in the mouse model. MDA-modified POS also significantly increased the expression of vascular endothelial growth factor and disrupted cell junctions in RPE cells. In addition, MDA-modified POS induced autophagy–lysosomal impairment in RPE cells.

Conclusions

Subretinal injection of MDA-modified POS may generate a feasible CNV model that simulates the AMD pathological process.

Translational Relevance

This study expands the understanding of the role of MDA in AMD pathogenesis, which provides a potential therapeutic target of AMD.

C20D3-Vitamin A Prevents Retinal Pigment Epithelium Atrophic Changes in a Mouse Model

Purpose

This study aimed to evaluate the contribution of vitamin A dimerization to retinal pigment epithelium (RPE) atrophic changes. Leading causes of irreversible blindness, including Stargardt disease and age-related macular degeneration (AMD), occur as a result of atrophic changes in RPE. The cause of the RPE atrophic changes is not apparent. During the vitamin A cycle, vitamin A dimerizes, leading to vitamin A cycle byproducts, such as vitamin A dimers, in the RPE.

Methods

To study the consequence of vitamin A dimerization to RPE atrophic changes, we used a rodent model with accelerated vitamin A dimerization, Abca4^−/−/Rdh8^−/− mice, and the vitamin A analog C20D₃-vitamin A to selectively ameliorate the accelerated rate of vitamin A dimerization.

Results

We show that ameliorating the rate of vitamin A dimerization with C20D₃-vitamin A mitigates pathological changes observed in the prodromal phase of the most prevalent retinal degenerative diseases, including fundus autofluorescence changes, dark adaptation delays, and signature RPE atrophic changes.

Conclusions

Data demonstrate that the dimerization of vitamin A during the vitamin A cycle is sufficient alone to cause the prerequisite RPE atrophic changes thought to be responsible for the leading causes of irreversible blindness and that correcting the dimerization rate with C20D₃-vitamin A may be sufficient to prevent the RPE atrophic changes.

Translational Relevance

Preventing the dimerization of vitamin A with the vitamin A analog C20D₃-vitamin A may be sufficient to alter the clinical course of the most prevalent forms of blindness, including Stargardt disease and age-related macular degeneration (AMD).

Temporary Upregulation of Nrf2 by Naringenin Alleviates Oxidative Damage in the Retina and ARPE-19 Cells

Dry age-related macular degeneration (dAMD) is a chronic degenerative ophthalmopathy that leads to serious burden of visual impairment. Antioxidation in retinal pigment epithelium (RPE) cells is considered as a potential treatment for dAMD. Our previous studies have showed that naringenin (NAR) protects RPE cells from oxidative damage partly through SIRT1-mediated antioxidation. In this study, we tested the hypothesis that the Nrf2 signaling is another protective mechanism of NAR on dAMD. NaIO₃-induced mouse retinopathy and ARPE-19 cell injury models were established. Immunochemical staining, immunofluorescence, and western blotting were performed to detect the protein expressions of Nrf2 and HO-1. In addition, ML385 (activity inhibitor of Nrf2) and zinc protoporphyrin (ZnPP, activity inhibitor of HO-1) were applied to explore the effect of NaIO₃ or NAR. The results showed that NAR increased the protein expressions of Nrf2 and HO-1 in the retinas in mice exposed to NaIO₃ at the early stage. NAR treatment also resulted in a stronger activation of Nrf2 at the early stage in NaIO₃-treated ARPE-19 cells. Moreover, inhibition of HO-1 by ZnPP weakened the cytoprotective effect of NAR. The constitutive accumulation and activation of Nrf2 induced by NaIO₃ led to the death of RPE cells. However, NAR decreased the protein expressions of Nrf2 and HO-1 towards normal level in the mouse retinas and ARPE-19 cells exposed to NaIO₃ at the late stage. Our findings indicate that NAR protects RPE cells from oxidative damage via activating the Nrf2 signaling pathway.

Extracellular vesicles released by human retinal pigment epithelium mediate increased polarised secretion of drusen proteins in response to AMD stressors

Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. Drusen are key contributors to the etiology of AMD and the ability to modulate drusen biogenesis could lead to therapeutic strategies to slow or halt AMD progression. The mechanisms underlying drusen biogenesis, however, remain mostly unknown. Here we demonstrate that under homeostatic conditions extracellular vesicles (EVs) secreted by retinal pigment epithelium (RPE) cells are enriched in proteins associated with mechanisms involved in AMD pathophysiology, including oxidative stress, immune response, inflammation, complement system and drusen composition. Furthermore, we provide first evidence that drusen-associated proteins are released as cargo of extracellular vesicles secreted by RPE cells in a polarised apical:basal mode. Notably, drusen-associated proteins exhibited distinctive directional secretion modes in homeostatic conditions and, differential modulation of this directional secretion in response to AMD stressors. These observations underpin the existence of a finely-tuned mechanism regulating directional apical:basal sorting and secretion of drusen-associated proteins via EVs, and its modulation in response to mechanisms involved in AMD pathophysiology. Collectively, our results strongly support an active role of RPE-derived EVs as a key source of drusen proteins and important contributors to drusen development and growth.

Erythropoietin Gene Therapy Delays Retinal Degeneration Resulting from Oxidative Stress in the Retinal Pigment Epithelium

Erythropoietin (EPO) plays an important role in erythropoiesis by its action in blocking apoptosis of progenitor cells and protects both photoreceptors and retinal ganglion cells from induced or inherited degeneration. A modified form of EPO, EPO-R76E has attenuated erythropoietic activity but is effective in inhibiting apoptosis, oxidative stress, and inflammation in several models of retinal degeneration. In this study, we used recombinant Adeno Associated Virus (AAV) to provide long-term sustained delivery of EPO-R76E and demonstrated its effects in a mouse model of dry-AMD in which retinal degeneration is induced by oxidative stress in the retinal pigment epithelial (RPE) cells. Experimental vector AAV-EPO-R76E and control vector AAV-GFP were packaged into serotype-1 (AAV1) to enable RPE selective expression. RPE oxidative stress-mediated retinal degeneration was induced by exon specific deletion of the protective enzyme MnSOD (encoded by Sod2) by cre/lox mechanism. Experimental mice received subretinal injection of AAV-EPO-R76E in the right eye and AAV-GFP in the left eye. Western blotting of RPE/choroid protein samples from AAV-EPO-R76E injected eyes showed RPE specific EPO expression. Retinal function was monitored by electroretinography (ERG). EPO-R76E over-expression in RPE delayed the retinal degeneration as measured by light microscopy in RPE specific Sod2 knockout mice. Delivery of EPO-R76E vector can be used as a tool to prevent retinal degeneration induced by RPE oxidative stress, which is implicated as a potential cause of Age-Related Macular Degeneration.

Distribution of polymeric nanoparticles in the eye: implications in ocular disease therapy

Advantages of polymeric nanoparticles as drug delivery systems include controlled release, enhanced drug stability and bioavailability, and specific tissue targeting. Nanoparticle properties such as hydrophobicity, size, and charge, mucoadhesion, and surface ligands, as well as administration route and suspension media affect their ability to overcome ocular barriers and distribute in the eye, and must be carefully designed for specific target tissues and ocular diseases. This review seeks to discuss the available literature on the biodistribution of polymeric nanoparticles and discuss the effects of nanoparticle composition and administration method on their ocular penetration, distribution, elimination, toxicity, and efficacy, with potential impact on clinical applications.

Photoreactivity of Bis-retinoid A2E Complexed with a Model Protein in Selected Model Systems

The bis-retinoid N-retinyl-N-retinylidene ethanolamine (A2E) is formed as a byproduct of visual cycle in retinal pigment epithelium (RPE). It contributes to golden-yellow fluorescence of the age pigment lipofuscin, which accumulates in RPE. Lipofuscin can generate a variety of reactive oxygen species (ROS) upon blue-light excitation. Although in model systems photoreactivity of A2E has been determined to be low, this bis-retinoid exhibited significant phototoxicity in RPE cells in vitro. Although the mechanism of A2E-mediated phototoxicity remains mostly unknown, we hypothesize that formation of A2E-adducts with different biomolecules may play an important role. In this study, we investigated the photochemical reactivity of A2E and its complex with bovine serum albumin (BSA) using UV-Vis absorption and emission spectroscopy, EPR-spin trapping, EPR-oximetry, time-resolved singlet oxygen phosphorescence, and the fluorogenic CBA probe. Our data show that A2E after complexation with this model protein photogenerated an increased level of ROS, particularly singlet oxygen. We also demonstrated the ability of A2E to oxidize BSA upon excitation with blue light in aqueous model systems. The data suggest that pyridinium bis-retinoid could oxidatively modify cellular proteins under physiological conditions.

Deep Learning-Based Classification of Inherited Retinal Diseases Using Fundus Autofluorescence

Background. In recent years, deep learning has been increasingly applied to a vast array of ophthalmological diseases. Inherited retinal diseases (IRD) are rare genetic conditions with a distinctive phenotype on fundus autofluorescence imaging (FAF). Our purpose was to automatically classify different IRDs by means of FAF images using a deep learning algorithm. Methods. In this study, FAF images of patients with retinitis pigmentosa (RP), Best disease (BD), Stargardt disease (STGD), as well as a healthy comparable group were used to train a multilayer deep convolutional neural network (CNN) to differentiate FAF images between each type of IRD and normal FAF. The CNN was trained and validated with 389 FAF images. Established augmentation techniques were used. An Adam optimizer was used for training. For subsequent testing, the built classifiers were then tested with 94 untrained FAF images. Results. For the inherited retinal disease classifiers, global accuracy was 0.95. The precision-recall area under the curve (PRC-AUC) averaged 0.988 for BD, 0.999 for RP, 0.996 for STGD, and 0.989 for healthy controls. Conclusions. This study describes the use of a deep learning-based algorithm to automatically detect and classify inherited retinal disease in FAF. Hereby, the created classifiers showed excellent results. With further developments, this model may be a diagnostic tool and may give relevant information for future therapeutic approaches.

Retinal Pigment Epithelial Detachment in Age-Related Macular Degeneration

Retinal pigment epithelial detachment is defined as a separation of the retinal pigment epithelium from the inner collagenous layer of Bruch’s membrane. It is a common manifestation in both dry and wet types of age-related macular degeneration. This review aims to provide a comprehensive guide to the pathophysiology, clinical and imaging characteristics, natural course and treatment of the various types of pigment epithelial detachments in order to assist in diagnosis and management of this important feature of age-related macular degeneration.

Pluripotent Stem Cells for the Treatment of Retinal Degeneration: Current Strategies and Future Directions

Stem cells have been part of the biomedical landscape since the early 1960s. However, the translation of stem cells to effective therapeutics have met significant challenges, especially for retinal diseases. The retina is a delicate and complex architecture of interconnected cells that are steadfastly interdependent. Degenerative mechanisms caused by acquired or inherited diseases disrupt this interconnectivity, devastating the retina and causing severe vision loss in many patients. Consequently, retinal differentiation of exogenous and endogenous stem cells is currently being explored as replacement therapies in the debilitating diseases. In this review, we will examine the mechanisms involved in exogenous stem cells differentiation and the challenges of effective integration to the host retina. Furthermore, we will explore the current advancements in trans-differentiation of endogenous stem cells, primarily Müller glia.

Microstructure of the retinal pigment epithelium near-infrared autofluorescence in healthy young eyes and in patients with AMD

Retinal pigmented epithelial (RPE) cells are essential for maintaining normal visual function, especially in their role in the visual cycle, and are thought to be one of the first cell classes affected by age-related macular degeneration (AMD). Clinical imaging systems routinely evaluate the structure of the RPE at the tissue level, but cellular level information may provide valuable RPE biomarkers of health, aging and disease. In this exploratory study, participants were imaged with 795 nm excitation in adaptive optics scanning laser ophthalmoscopy (AOSLO) to observe the microstructure of the near-infrared autofluorescence (AO-IRAF) from the RPE layer in healthy retinas and patients with AMD. The expected hexagonal mosaic of RPE cells was only sometimes seen in normal eyes, while AMD patients exhibited highly variable patterns of altered AO-IRAF. In some participants, AO-IRAF structure corresponding to cones was observed, as we have demonstrated previously. In some AMD patients, marked alterations in the pattern of AO-IRAF could be seen even in areas where the RPE appeared relatively normal in clinical imaging modalities, such as spectral domain optical coherence tomography (SD-OCT). AO-IRAF imaging using AOSLO offers promise for better detection and understanding of early RPE changes in the course of AMD, potentially before clinical signs appear.

Omega-3 fatty acids supplementation protects the retina from age-associated degeneration in aged C57BL/6J mice

Objective

To evaluate the therapeutic effects of omega-3 (ω3) fatty acids in the retina of aged mice when the blood arachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio is maintained between 1.0 and 1.5.

Methods and analysis

Aged (24-month-old) wild-type C57BL/6J mice were allocated to two groups: ω3 treated and untreated. Treatment with ω3 was by daily gavage administration of EPA and docosahexaenoic acid for 60 days. Gas chromatography was used to identify and quantify fatty acids in the blood and retina. To count lipofuscin granules and measure the photoreceptor layer, eyecups were examined histologically using transmission electron microscopy and light microscopy. We also analysed eyecups using mass spectrometry-based proteomics.

Results

AA levels were lower, and EPA levels were higher, in the blood and retinas of the ω3-treated group than in the untreated group, resulting in a lower AA/EPA ratio. The ω3-treated group also showed significantly fewer lipofuscin granules and a thicker outer nuclear layer than the untreated group. Proteomic analysis revealed significantly greater expression of myelin basic protein, myelin regulatory factor-like protein, myelin proteolipid protein and glial fibrillar acidic protein in the ω3-treated group than in the untreated group. Three different pathways were significantly affected by ω3 treatment: fatty acid elongation, biosynthesis of unsaturated fatty acids and metabolic pathways.

Conclusion

Two months of ω3 supplementation (when the blood AA/EPA~1.0-1.5) in aged mice reduced lipofuscin granule formation in the retina and protected the photoreceptor layer, suggesting that ω3 supplementation slows normal age-related retinal degeneration.

Radiation Therapy for Benign Disease: Keloids, Macular Degeneration, Orbital Pseudotumor, Pterygium, Peyronie Disease, Trigeminal Neuralgia

Although the use of ionizing radiation on malignant conditions has been well established, its application on benign conditions has not been fully accepted and has been inadequately recognized by health care providers outside of radiation therapy. Most frequently, radiation therapy in these benign conditions is used along with other treatment modalities, such as surgery, when the condition causes significant disability or could even lead to death. Radiation therapy can be helpful for inflammatory/proliferative disorders. This article discusses the present use of radiation therapy for some of the most common benign conditions.

Applications of microneedles in delivering drugs for various ocular diseases

Treatment of majority of eye diseases involve the use of eye drops or eye ointments, which have major drawbacks of needing frequent administration, lower bioavailability and inability to cross the various eye barriers. This necessitates the use of novel delivery systems. Microneedles (MNs) as an alternate novel delivery system facilitate drug delivery to various ocular diseases with promising approaches in healthcare. Advances in pharmaceutical technology have made MNs provide localized, effective, less invasive and targeted drug delivery in the eye. The purpose of this review is to provide an insight to efficacious therapeutic applications the MNs can bring in various ocular diseases. Out of which, glaucoma, age-related macular degeneration, uveitis, retinal vascular occlusion and retinitis pigmentosa are majorly discussed. Among the various types of MNs; solid coated, hollow and dissolving polymeric MNs are specifically focused for their applications in ocular diseases. In addition, MNs shows improvement in the visual acuity and decreases the progression of the different ocular diseases.

Zeaxanthin: Metabolism, Properties, and Antioxidant Protection of Eyes, Heart, Liver, and Skin

Zeaxanthin, a non-provitamin A carotenoid that belongs to the xanthophyll family, has been less studied than its isomer lutein. However, zeaxanthin has also been shown to have a number of beneficial effects for human health due to its ability to quench free radicals, exert antioxidant effects, as well as decrease inflammation. It is the purpose of this review to discuss the metabolism of zeaxanthin, including digestion, absorption, transport, and uptake by tissues, as well as the dietary or other factors which affect zeaxanthin bioavailability. In addition, this review also focuses on specific effects of this carotenoid on eye, skin, liver, and cardiovascular health. Data derived from human interventions, animal models of research, and in vitro and cell studies are discussed in this review.

CAPTCHA as a Visual Performance Metric in Active Macular Disease

Purpose

CAPTCHA (completely automated public turing test to tell computers and humans apart) was designed as a spam prevention test. In patients with visual impairment, completion of this task has been assumed to be difficult; but to date, no study has proven this to be true. As visual function is not well measured by Snellen visual acuity (VA) alone, we theorized that CAPTCHA performance may provide additional information on macular disease-related visual dysfunction.

Methods

This was designed as a pilot study. Active disease was defined as the presence of either intraretinal fluid (IRF) or subretinal fluid (SRF) on spectral-domain optical coherence tomography. CAPTCHA performance was tested using 10 prompts. In addition, near and distance VA, contrast sensitivity, and reading speed were measured. Visual acuity matched pseudophakic patients were used as controls. Primary outcome measures were average edit distance and percent of correct responses.

Results

70 patients were recruited: 33 with active macular disease and 37 control subjects. Contrast sensitivity was found to be significantly different in both the IRF (p < 0.01) and SRF groups (p < 0.01). No significant difference was found comparing the odds ratio of average edit distance of active disease (IRF, SRF) vs. control (OR 1.09 (0.62, 1.90), 1.10 (0.58, 2.05), p=0.77,  0.77) or percent correct responses of active disease vs. control (OR 0.98 (0.96, 1.01), 1.09 (0.58, 2.05), p=0.22, 0.51) in CAPTCHA testing. The goodness of fit using logistic regression analysis for the dependent variables of either IRF or SRF did not improve accounting for average edit distance (p=0.49,  p=0.27) or percent correct (p=0.89,  p=0.61).

Conclusions

Distance VA and contrast sensitivity are positively correlated with the presence of IRF and SRF in active macular disease. CAPTCHA performance did not appear to be a significant predictor of either IRF or SRF in our pilot study.

Progesterone, Lipoic Acid, and Sulforaphane as Promising Antioxidants for Retinal Diseases: A Review

Oxidative stress has been documented to be a key factor in the cause and progression of different retinal diseases. Oxidative cellular unbalance triggers a sequence of reactions which prompt cell degeneration and retinal dysfunction, both hallmarks of several retinal pathologies. There is no effective treatment, yet, for many retinal diseases. Antioxidant treatment have been pointed out to be an encouraging palliative treatment; the beneficial effects documented involve slowing the progression of the disease, a reduction of cell degeneration, and improvement of retinal functions. There is a vast information corpus on antioxidant candidates. In this review, we expose three of the main antioxidant treatments, selected for their promising results that has been reported to date. Recently, the sulforaphane, an isothiocyanate molecule, has been unveiled as a neuroprotective candidate, by its antioxidant properties. Progesterone, a neurosteroid has been proposed to be a solid and effective neuroprotective agent. Finally, the lipoic acid, an organosulfur compound, is a well-recognized antioxidant. All of them, have been tested and studied on different retinal disease models. In this review, we summarized the published results of these works, to offer a general view of the current antioxidant treatment advances, including the main effects and mechanisms described.

On the origin of proteins in human drusen: The meet, greet and stick hypothesis

Retinal drusen formation is not only a clinical hallmark for the development of age-related macular degeneration (AMD) but also for other disorders, such as Alzheimer's disease and renal diseases. The initiation and growth of drusen is poorly understood. Attention has focused on lipids and minerals, but relatively little is known about the origin of drusen-associated proteins and how they are retained in the space between the basal lamina of the retinal pigment epithelium and the inner collagenous layer space (sub-RPE-BL space). While some authors suggested that drusen proteins are mainly derived from cellular debris from processed photoreceptor outer segments and the RPE, others suggest a choroidal cell or blood origin. Here, we reviewed and supplemented the existing literature on the molecular composition of the retina/choroid complex, to gain a more complete understanding of the sources of proteins in drusen. These "drusenomics" studies showed that a considerable proportion of currently identified drusen proteins is uniquely originating from the blood. A smaller, but still large fraction of drusen proteins comes from both blood and/or RPE. Only a small proportion of drusen proteins is uniquely derived from the photoreceptors or choroid. We next evaluated how drusen components may "meet, greet and stick" to each other and/or to structures like hydroxyapatite spherules to form macroscopic deposits in the sub-RPE-BL space. Finally, we discuss implications of our findings with respect to the previously proposed homology between drusenogenesis in AMD and plaque formation in atherosclerosis.

Overexpression of acid ceramidase (ASAH1) protects retinal cells (ARPE19) from oxidative stress

Over 11 million people in the United States alone have some form of age-related macular degeneration (AMD). Oxidative stress, cell death, and the degeneration of retinal pigment epithelial (RPE) cells contribute to AMD pathology. Recent evidence suggests that ceramide (Cer), a cellular sphingolipid mediator that acts as a second messenger to induce apoptosis, might play a role in RPE cell death. The lysosomal breakdown of Cer by acid ceramidase [N-acylsphingosine amidohydrolase (ASAH)1] into sphingosine (Sph) is the major source for Sph 1-phosphate production, which has an opposing role to Cer and provides cytoprotection. Here, we investigated the role of Cer in human RPE-derived ARPE19 cells under hydrogen peroxide-induced oxidative stress, and show that Cer and hexosyl-Cer levels increase in the oxidatively stressed ARPE19 cells, which can be prevented by overexpression of lysosomal ASAH1. This study demonstrates that oxidative stress generates sphingolipid death mediators in retinal cells and that induction of ASAH1 could rescue retinal cells from oxidative stress by hydrolyzing excess Cers.

Fundus autofluorescence imaging in hereditary retinal diseases

Fundus autofluorescence (FAF) is a non-invasive retinal imaging modality used in clinical practice to non-invasively map changes at the level of the retinal pigment epithelium (RPE)/photoreceptor complex and alterations of macular pigment distribution. This imaging method is based on the visualization of intrinsic fluorophores and may be easily and rapidly used in routine patient care. Excessive accumulation of lipofuscin granules in the lysosomal compartment of RPE cells represents a common downstream pathogenic pathway in various hereditary and complex retinal diseases. The clinical applications of FAF continue to expand. It is now an essential tool for evaluating macular dystrophies and various hereditary retinal disorders. Fundus autofluorescence (FAF) may detect abnormalities beyond those detected on funduscopic examination, fluorescein angiography (FA) or optical coherence tomography (OCT). Fundus autofluorescence (FAF) imaging is particularly helpful for differential diagnosis, detection and extent delineation of involved retinal areas, genotype-phenotype correlations and monitoring of changes overtime. Given its ease of use, non-invasive nature and value in characterizing retinal disease, FAF enjoys increasing clinical relevance. This review summarizes basic principles and FAF findings in various hereditary retinal diseases.

Autofluorescence in a Patient with Adult Vitelliform Degeneration

The case of an 83 year-old woman is presented in whom bilateral vitelliform macular cysts were observed to fluoresce during the pre-injection phase of intravenous fluorescein angiography. This suggests that the vitelliform response is a non-specific event occurring in retinal pigment epithelial disease in which lipofuscin may or may not be manufactured.

Age-related macular degeneration changes the processing of visual scenes in the brain

In age-related macular degeneration (AMD), the processing of fine details in a visual scene, based on a high spatial frequency processing, is impaired, while the processing of global shapes, based on a low spatial frequency processing, is relatively well preserved. The present fMRI study aimed to investigate the residual abilities and functional brain changes of spatial frequency processing in visual scenes in AMD patients. AMD patients and normally sighted elderly participants performed a categorization task using large black and white photographs of scenes (indoors vs. outdoors) filtered in low and high spatial frequencies, and nonfiltered. The study also explored the effect of luminance contrast on the processing of high spatial frequencies. The contrast across scenes was either unmodified or equalized using a root-mean-square contrast normalization in order to increase contrast in high-pass filtered scenes. Performance was lower for high-pass filtered scenes than for low-pass and nonfiltered scenes, for both AMD patients and controls. The deficit for processing high spatial frequencies was more pronounced in AMD patients than in controls and was associated with lower activity for patients than controls not only in the occipital areas dedicated to central and peripheral visual fields but also in a distant cerebral region specialized for scene perception, the parahippocampal place area. Increasing the contrast improved the processing of high spatial frequency content and spurred activation of the occipital cortex for AMD patients. These findings may lead to new perspectives for rehabilitation procedures for AMD patients.

Color Doppler Imaging of the Retrobulbar Circulation in Age-Related Macular Degeneration

Purpose

The aim of this study was to assess hemodynamic changes in the retrobulbar circulation in patients with age-related macular degeneration (ARMD).

Methods

Color Doppler imaging was used to calculate blood flow velocities and vascular resistance of the central retinal artery, short posterior ciliary artery and ophthalmic artery in patients with ARMD and in control patients.

Results

The average peak systolic velocity was significantly lower in the central retinal artery (p < 0.001), posterior ciliary artery (p < 0.001) and ophthalmic artery (p < 0.01) of the patients with ARMD than in control. End-diastolic blood flow velocities in the retrobulbar arteries of ARMD patients were also significantly lower (p < 0.001) than controls. Gosling's pulsatility index was significantly higher in the ophthalmic artery (p<0.01) and posterior ciliary artery (p < 0.001) of eyes with ARMD. In addition, the resistivity index was significantly higher in all retrobulbar arteries (p < 0.001) of these patients.

Conclusions

The hemodynamic abnormalities in the retrobulbar circulation suggest that vascular impairment may play a role in the pathogenesis of ARMD.

Decreased severity of age-related macular degeneration in amblyopic eyes

AIM

To evaluate whether people with age-related macular degeneration (AMD) and a history of amblyopia have equal severity of AMD in both eyes.

METHODS

Billing records were used to locate all people with a history of amblyopia and AMD evaluated between 1 January 2003 and 1 June 2015 at a single ophthalmology institute. Two ophthalmic graders blinded to amblyopia status determined the severity of AMD in each eye using fundus photos and a validated grading scale.

RESULTS

A total of 14 people were found to have AMD and a documented history of amblyopia. Average patient age was 77.0 years and average best corrected visual acuity was 20/160 in eyes with a history of amblyopia and 20/40 in fellow eyes without amblyopia. Eyes with a history of amblyopia were found to have a lower AMD severity score (mean lower score: -1.38; paired t-test P=0.019). Of the 11 people with asymmetric disease severity, 10 individuals had worse AMD in the non-amblyopic eye while one person had worse AMD in the amblyopic eye (P=0.0067).

CONCLUSIONS

Our pilot study suggests that eyes with a history of amblyopia may manifest decreased severity of AMD compared with non-ambylopic eyes in the same patient. Further research is warranted to investigate this clinical observation.