Electroretinography in glaucoma diagnosis

The Use of the RETeval Portable Electroretinography Device for Low-Cost Screening: A Mini-Review

Electroretinography (ERG) provides crucial insights into retinal function and the integrity of the visual pathways. However, ERG assessments classically require a complicated technical background with costly equipment. In addition, the placement of corneal or conjunctival electrodes is not always tolerated by the patients, which restricts the measurement for pediatric evaluations. In this short review, we give an overview of the use of the RETeval portable ERG device (LKC Technologies, Inc., Gaithersburg, MD, USA), a modern portable ERG device that can facilitate screening for diseases involving the retina and the optic nerve. We also review its potential to provide ocular biomarkers in systemic pathologies, such as Alzheimer's disease and central nervous system alterations, within the framework of oculomics.

Sensitivity and specificity of the uniform field electroretinogram in glaucoma detection in comparison to the pattern electroretinogram

PURPOSE

To determine the ability of the photopic negative response (PhNR) of the uniform field electroretinogram (UF-ERG) to identify early glaucomatous changes in comparison to the checkerboard and bar stimuli of the pattern electroretinogram (PERG).

METHODS

Forty-nine glaucoma patients were classified into two groups: glaucoma-suspect (23 eyes) and early to moderate glaucoma (30 eyes), based on their clinical examination and the results of standard automated perimetry. Thirty patients (30 eyes) with intraocular pressures (IOP) of 21 mmHg or less, with no history of reported high IOP, were included as controls. PERG and UF-ERG recordings were obtained on a Diagnosys D-341 Attaché-Envoy System. Visual field testing was done only for glaucoma-suspect and glaucoma patients.

RESULTS

All three tests (PERG bar stimulus, PERG checkerboard stimulus and PhNR) displayed significantly prolonged peak times for glaucoma and glaucoma-suspect patients, with delays ranging from 7.8 to 14.8%, depending on the test. The PERG bar stimulus also showed a significantly lower N95 amplitude for both glaucoma groups (with reductions of 26.0% and 33.0% for glaucoma-suspect and glaucoma groups, respectively). The PERG checkerboard N95 amplitude component had high sensitivity for detecting glaucoma patients but a low specificity (97% and 37%, respectively; AUC = 0.61). Overall, the PhNR peak time showed the highest sensitivity and specificity (77% and 90%, respectively; AUC = 0.87).

CONCLUSIONS

PERG bar stimuli and the PhNR of the UF-ERG can be used in the clinical setting to detect glaucoma-related changes in glaucoma-suspect and glaucoma patients. However, our data confirm that the PhNR peak time has the best combined sensitivity and specificity.

Biologically Driven In Vivo Occlusion Design Provides a Reliable Experimental Glaucoma Model

Fluid flow transport through the trabecular meshwork tissues is a major regulator of intraocular pressure (IOP) modulation in healthy and glaucomatous individuals. Microbead occlusion models of ocular hypertension regulate aqueous humor drainage to induce high IOP to allow for in vivo study of pressure-related glaucomatous pathology. However, the reliability and application of current injectable microbeads are hindered by inadequate design of the beads-tissue interfaces to maintain a stable IOP elevation over the long term. Considering the graded, porous architecture and fluid transport of the trabecular meshwork, we developed a tailored, injectable "viscobeads" technique, which induced a sustained elevation of IOP for at least 8 weeks. These composite viscobeads contain a non-degradable polystyrene (PS) core for structural support and a biodegradable polylactic-co-glycolic acid (PLGA) viscoelastic surface. This approach enhances the obstruction of aqueous humor drainage through heterogeneous sizes of trabecular meshwork fenestrations and reliably modulates the magnitude and duration of ocular hypertension. In a mouse model, a single viscobeads injection resulted in sustained IOP elevation (average 21.4±1.39 mm Hg), leading to a 34% retinal ganglion cell (RGC) loss by 56 days. In an earlier stage of glaucoma progression, we conducted non-invasive electroretinography (ERG) recording and revealed glaucomatous progression by analyzing high-frequency oscillatory potentials. To further explore the application of the viscobeads glaucoma models, we assayed a series of genes through adeno-associated virus (AAV)-mediated screening in mice and assessed the impact of genetic manipulation on RGC survivals. CRISPR mediated disruption of the genes, PTEN, ATF3 and CHOP enhanced RGC survival while LIN 28 disruption negatively impacted RGC survival. This biologically driven viscobeads design provides an accessible approach to investigate chronic intraocular hypertension and glaucoma-like neurodegeneration and ultimately tenders the opportunity to evaluate genetic and pharmacological therapeutics.

Chronic Glaucoma Induced in Rats by a Single Injection of Fibronectin-Loaded PLGA Microspheres: IOP-Dependent and IOP-Independent Neurodegeneration

To evaluate a new animal model of chronic glaucoma induced using a single injection of fibronectin-loaded biodegradable PLGA microspheres (Ms) to test prolonged therapies. 30 rats received a single injection of fibronectin-PLGA-Ms suspension (MsF) in the right eye, 10 received non-loaded PLGA-Ms suspension (Control), and 17 were non-injected (Healthy). Follow-up was performed (24 weeks), evaluating intraocular pressure (IOP), optical coherence tomography (OCT), histology and electroretinography. The right eyes underwent a progressive increase in IOP, but only induced cohorts reached hypertensive values. The three cohorts presented a progressive decrease in ganglion cell layer (GCL) thickness, corroborating physiological age-related loss of ganglion cells. Injected cohorts (MsF > Control) presented greater final GCL thickness. Histological exams explain this paradox: the MsF cohort showed lower ganglion cell counts but higher astrogliosis and immune response. A sequential trend of functional damage was recorded using scotopic electroretinography (MsF > Control > Healthy). It seems to be a function-structure correlation: in significant astrogliosis, early functional damage can be detected by electroretinography, and structural damage can be detected by histological exams but not by OCT. Males presented higher IOP and retinal and GCL thicknesses and lower electroretinography. A minimally invasive chronic glaucoma model was induced by a single injection of biodegradable Ms.

The Role of Retinal Ganglion Cell Structure and Function in Glaucoma

Glaucoma, a leading cause of irreversible blindness globally, primarily affects retinal ganglion cells (RGCs). This review dives into the anatomy of RGC subtypes, covering the different underlying theoretical mechanisms that lead to RGC susceptibility in glaucoma, including mechanical, vascular, excitotoxicity, and neurotrophic factor deficiency, as well as oxidative stress and inflammation. Furthermore, we examined numerous imaging methods and functional assessments to gain insight into RGC health. Finally, we investigated the current possible neuroprotective targets for RGCs that could help with future glaucoma research and management.

Retinal Microenvironment-Protected Rhein-GFFYE Nanofibers Attenuate Retinal Ischemia-Reperfusion Injury via Inhibiting Oxidative Stress and Regulating Microglial/Macrophage M1/M2 Polarization

Retinal ischemia is involved in the occurrence and development of various eye diseases, including glaucoma, diabetic retinopathy, and central retinal artery occlusion. To the best of our knowledge, few studies have reported self-assembling peptide natural products for the suppression of ocular inflammation and oxidative stress. Herein, a self-assembling peptide GFFYE is designed and synthesized, which can transform the non-hydrophilicity of rhein into an amphiphilic sustained-release therapeutic agent, and rhein-based therapeutic nanofibers (abbreviated as Rh-GFFYE) are constructed for the treatment of retinal ischemia-reperfusion (RIR) injury. Rh-GFFYE significantly ameliorates oxidative stress and inflammation in an in vitro oxygen-glucose deprivation (OGD) model of retinal ischemia and a rat model of RIR injury. Rh-GFFYE also significantly enhances retinal electrophysiological recovery and exhibits good biocompatibility. Importantly, Rh-GFFYE also promotes the transition of M1-type macrophages to the M2 type, ultimately altering the pro-inflammatory microenvironment. Further investigation of the treatment mechanism indicates that Rh-GFFYE activates the PI3K/AKT/mTOR signaling pathway to reduce oxidative stress and inhibits the NF-κB and STAT3 signaling pathways to affect inflammation and macrophage polarization. In conclusion, the rhein-loaded nanoplatform alleviates RIR injury by modulating the retinal microenvironment. The findings are expected to promote the clinical application of hydrophobic natural products in RIR injury-associated eye diseases.

CREG Protects Retinal Ganglion Cells loss and Retinal Function Impairment Against ischemia-reperfusion Injury in mice via Akt Signaling Pathway

PURPOSE

The irreversible death of retinal ganglion cells (RGCs) plays an important role in the pathogenesis of glaucoma. Cellular repressor of E1A-stimulated genes (CREG), a secreted glycoprotein involved in cellular proliferation and differentiation, has been shown to protect against myocardial and renal ischemia-reperfusion damage. However, the role of CREG in retinal ischemia-reperfusion injury (RIRI) remains unknown. In this study, we aimed to explore the effect of CREG on RGCs apoptosis after RIRI.

METHODS

We used male C57BL/6J mice to establish the RIRI model. Recombinant CREG was injected at 1 day before RIRI. The expression and distribution of CREG were examined by immunofluorescence staining and western blotting. RGCs survival was assessed by immunofluorescence staining of flat-mounted retinas. Retinal apoptosis was measured by the staining of TdT-mediated dUTP nick-end labeling and cleaved caspase-3. Electroretinogram (ERG) analysis and optomotor response were conducted to evaluate retinal function and visual acuity. The expressions of Akt, phospho-Akt (p-Akt), Bax, and Bcl-2 were analyzed by western blotting to determine the signaling pathways of CREG.

RESULTS

We found that CREG expression was decreased after RIRI, and intravitreal injection of CREG attenuated RGCs loss and retinal apoptosis. Besides, the amplitudes of a-wave, b-wave, and photopic negative response (PhNR) in ERG, as well as visual function, were significantly restored after treatment with CERG. Furthermore, intravitreal injection of CREG upregulated p-Akt and Bcl-2 expression and downregulated Bax expression.

CONCLUSION

Our results demonstrated that CREG protected RGCs from RIRI and alleviated retinal apoptosis by activating Akt signaling. In addition, CREG also improved retinal function and visual acuity.

Intraocular Adeno-Associated Virus-Mediated Transgene Endothelin-1 Delivery to the Rat Eye Induces Functional Changes Indicative of Retinal Ischemia-A Potential Chronic Glaucoma Model

Endothelin-1 (ET-1) overactivity has been implicated as a factor contributing to glaucomatous neuropathy, and it has been utilized in animal models of retinal ischemia. The functional effects of long-term ET-1 exposure and possible compensatory mechanisms have, however, not been investigated. This was therefore the purpose of our study. ET-1 was delivered into rat eyes via a single intravitreal injection of 500 µM or via transgene delivery using an adeno-associated viral (AAV) vector. Retinal function was assessed using electroretinography (ERG) and the retinal expression of potentially compensatory genes was evaluated by means of qRT-PCR. Acute ET-1 delivery led to vasoconstriction and a significant reduction in the ERG response. AAV-ET-1 resulted in substantial transgene expression and ERG results similar to the acute ET-1 injections and comparable to other models of retinal ischemia. Compensatory changes were observed, including an increase in calcitonin gene-related peptide (CGRP) gene expression, which may both counterbalance the vasoconstrictive effects of ET-1 and provide neuroprotection. This chronic ET-1 ischemia model might be especially relevant to glaucoma research, mimicking the mild and repeated ischemic events in patients with long-term vascular dysfunction. The compensatory mechanisms, and particularly the role of vasodilatory CGRP in mitigating the retinal damage, warrant further investigation with the aim of evaluating new therapeutic strategies.

Utility of Light-Adapted Full-Field Electroretinogram ON and OFF Responses for Detecting Glaucomatous Functional Damage

Purpose

To compare parameters of electroretinogram (ERG) responses for their ability to detect functional loss in early stages of nonhuman primate (NHP) experimental glaucoma (EG), including photopic negative responses (PhNR) to a standard brief red flash on a blue background (R/B) and 200-ms-long R/B and white-on-white (W/W) flashes, to W/W flicker stimuli (5-50 Hz), and to a dark-adapted intensity series.

Methods

Light-adapted ERGs were recorded in 12 anesthetized monkeys with unilateral EG. Amplitudes and implicit times of the a-wave, b-wave, and d-wave were measured, as well as amplitudes of PhNRs and oscillatory potentials for flash onset and offset. Flicker ERGs were measured using peak-trough and fundamental frequency analyses. Dark-adapted ERG parameters were modeled by Naka-Rushton relationships.

Results

Only PhNR amplitudes were significantly reduced in EG eyes compared to fellow control (FC) eyes. The d-wave implicit time was delayed in EG versus FC eyes only for the W/W long flash, but in all eyes it was 10 to 20 ms slower for R/B versus the W/W condition. Flicker ERGs were <0.5 ms delayed in EG versus FC overall, but amplitudes were affected only at 5 Hz. The brief R/B PhNR amplitude had the highest sensitivity to detect EG and strongest correlation to parameters of structural damage.

Conclusions

The PhNR to the standard brief R/B stimulus was best for detecting and following early-stage functional loss in NHP EG.

Translational Relevance

These results suggest that there would be no benefit in using longer duration flashes to separate onset and offset responses for clinical management of glaucoma.

Investigating the Structural and Functional Changes in the Optic Nerve in Patients with Early Glaucoma Using the Optical Coherence Tomography (OCT) and RETeval System

The present manuscript introduces an investigation of the structural and functional changes in the optic nerve in patients undergoing glaucoma treatment by comparing optical coherence tomography (OCT) measurements and RETeval system parameters. For such a purpose, 140 eyes were examined at the Ophthalmology Clinic of the "Elpis" General Hospital of Athens between October 2022 and April 2023. A total of 59 out of 140 eyes were from patients with early glaucoma under treatment (case group), 63 were healthy eyes (control group) and 18 were excluded. The experimental measurements were statistically analyzed using the SPSS software package. The main outcomes are summarized below: (i) there was no statistical difference between the right and left eye for both groups, (ii) statistical differences were found between age interval subgroups (30-54 and 55-80 years old) for the control group, mainly for the time response part of the RETeval parameters. Such difference was not indicated by the OCT system, and (iii) a statistical difference occurred between the control and case group for both OCT (through the retinal nerve fiber layer-RNFL thickness) and the RETeval parameters (through the photopic negative response-PhNR). RNFL was found to be correlated to b-wave (ms) and W-ratio parameters. In conclusion, the PhNR obtained by the RETeval system could be a valuable supplementary tool for the objective examination of patients with early glaucoma.

Use of multifocal electroretinograms to determine stage of glaucoma

PURPOSE

To determine whether multifocal electroretinograms (mfERGs) recorded with natural pupils and skin electrodes can be used to determine the stage of open angle glaucoma (OAG).

METHODS

Two hundred eighteen eyes of 132 OAG patients and 62 eyes of 62 normal subjects whose best-corrected visual acuity (BCVA) was 0.1 logarithm of the minimum angle of resolution (logMAR) units (20/25) or less were studied. The mean deviations (MDs) obtained by Humphrey Visual Field Analyzer (HFA), optical coherence tomographic (OCT) images, and mfERGs were analyzed. The glaucoma was classified into 4 stages: preperimetric glaucoma (PPG), early stage, moderate stage, and advanced stage glaucoma. The parameters of the mfERGs examined were the amplitudes of the two positive peaks (P1, P2) of the second order kernels in the nasal and temporal fields within the central 15° diameter.

RESULTS

The mean age of all participants (patients and normals) was 63.8 ± 10.8 years. With the progression of glaucoma, the amplitudes of P1 in the nasal hemifield increased and the amplitudes of P2 decreased. The nasal to temporal ratio (N/T ratio) of the P1 amplitudes and the negative slope of the line between P1 and P2 (P1P2 Slope) in the nasal field were larger at each glaucoma stage except at the PPG stage. Both the N/T amplitude ratio and P1P2 Slope were weakly but significantly correlated with the MD (r = -0.3139, P<0.0001; r = 0.4501, P<0.0001, respectively), and the OCT parameters (all P<0.0001) except the outer layer thickness.

CONCLUSIONS

Our findings indicate that the amplitudes of P1 and P2 of the second order kernel of the mfERGs in the nasal field of the center region can be good markers for the stages of glaucoma.

Measuring the Full-Field Electroretinogram in Rodents

Electroretinography allows for noninvasive functional assessment of the retina and is a mainstay for preclinical studies of retinal function in health and disease. The full-field electroretinogram is useful for a variety of applications as it returns a functional readout from each of the major cell classes within the retina: photoreceptors, bipolar cells, amacrine cells, and retinal ganglion cells. Rodent models are commonly employed in ocular degeneration studies due to the fast throughput of these mammalian species and the conservation of the electroretinogram from the preclinic to the clinic. Here we describe approaches for in vivo electroretinography in rodent models.

Non-Invasive Electroretinogram Recording with Simultaneous Optogenetics to Dissect Retinal Ganglion Cells Electrophysiological Dynamics

Electroretinography (ERG) is a non-invasive electrophysiological recording technique that detects the electrical signaling of neuronal cells in the visual system. In conventional ERG recordings, the signals are considered a collective electrical response from various neuronal cell populations, including rods, cones, bipolar cells, and retinal ganglion cells (RGCs). However, due to the limited ability to control electrophysiological responses from different types of cells, the detailed information underlying ERG signals has not been analyzed and interpreted. Linking the features of ERG signals to the specific neuronal response will advance the understanding of neuronal electrophysiological dynamics and provide more evidence to elucidate pathological mechanisms, such as RGC loss during the progression of glaucoma. Herein, we developed an advanced ERG recording system integrated with a programmable, non-invasive optogenetic stimulation method in mice. In this system, we applied an automatic and unbiased ERG data analysis approach to differentiate a, b wave, negative response, and oscillatory potentials. To differentiate the electrophysiological response of RGCs in ERG recordings, we sensitized mouse RGCs with red-light opsin, ChRmine, through adeno-associated virus (AAV) intravitreal injection. Features of RGC dynamics under red-light stimulation were identified in the ERG readout. This non-invasive ERG recording system, associated with the programmable optogenetics stimulation method, provides a new methodology to dissect neural dynamics under variable physiological and pathological conditions in vivo. With the merits of non-invasiveness, improved sensitivity, and specificity, we envision this system can be further applied for early-stage detection of RGC degeneration and functional progression in neural degenerative diseases, such as glaucoma.

Optical coherence tomography and electrophysiological analysis of proptotic eyes due to thyroid-associated ophthalmopathy

Purpose

To study the degree of morphological and functional changes in thyroid-associated ophthalmology (TAO) patients using optical coherence tomography and electrophysiological studies and investigate their clinical correlation.

Methods

A cross-sectional study including 40 patients with TAO and a control group with age- and sex-matched healthy subjects. All subjects underwent a complete ophthalmological examination, proptosis evaluation, spectral domain optical coherence tomography, and electrophysiological tests (pattern and multifocal electroretinograms, and visual evoked potentials).

Results

On multiple regression analysis, the degree of proptosis and P50 amplitude were the most important predictors of central foveal thickness (CFT) (β =  −  0.56 and 0.39 and p = 0.03 and 0.01, respectively); while duration of the disease, and clinical activity score (CAS) were the most important predictors of average RNFL thickness (β = 0.67 and  − 0.81 and p = 0.004 and  <  0.001, respectively).

Conclusion

In the absence of fundus changes, macular thinning along with functional alterations noticed by pattern and multifocal electroretinogram could indicate presence of subclinical retinopathy in TAO cases.

Predicting Visual Field Progression by Optical Coherence Tomography Angiography and Pattern Electroretinography in Glaucoma

PRCIS

Reduced P50-N95 amplitude on pattern electroretinography (PERG) and the presence of microvasculature dropout (MvD) on optical coherence tomography angiography (OCT-A) at baseline were significant factors associated with visual field (VF) progression in predominantly normal tension glaucoma (NTG) patients.

OBJECTIVE

We investigated the baseline demographics and ocular characteristics that predict future progression in glaucoma patients, including PERG and OCT-A parameters.

METHODS

One Hundred forty eyes with open angle glaucoma that were prospectively enrolled and followed up for at least 3 years, and underwent at least 5 serial VF tests were included. Baseline PERG was performed, and N35, P50, and N95 latencies and amplitudes were obtained. Superficial vessel density at the macula and complete loss of microvasculature within the deep retinal layer of the parapapillary region (MvD) were evaluated from baseline OCT-A images. Eyes with a glaucomatous VF defect in either both hemifields within 24 points of a central 10 degrees of fixation, and with no VF abnormality in the nasal periphery outside 10 degrees of fixation, were considered to have isolated central scotoma. During follow-up, detected disc hemorrhage (DH) was recorded. Parameters associated with VF progression were determined using linear regression analysis of the mean deviation (MD) values, in combination with an event-based analysis using the Glaucoma Progression Analysis (GPA) software from the Humphrey Field Analyzer. "Likely progression" using GPA was considered to have glaucoma progression.

RESULTS

Of the 140 eyes, 107 (76.4%) were NTG and 57 (40.7%) exhibited glaucoma progression as defined by Humphrey VF GPA. The MD slopes were -0.43±1.11 dB/y in the progressors and 0.59±1.27 dB/y in the nonprogressors ( P <0.001). Glaucoma patients with progression showed frequent MvD on OCT-A, isolated central scotoma, frequent DH, and reduced baseline P50-N95 amplitude compared with patients without progression. Age at diagnosis ( P =0.038) and baseline P50-N95 amplitude ( P =0.019) showed significant associations with the MD slope. The presence of MvD on OCT-A ( P <0.001) and baseline P50-N95 amplitude ( P =0.037) were significantly associated with VF progression on GPA.

CONCLUSIONS

The presence of MvD and retinal ganglion cell dysfunction by PERG at baseline, DH or central scotoma were significant factors associated with VF progression in predominantly NTG patients. These patients should be monitored more closely.

Influences of Glaucoma on the Structure and Function of Synapses in the Visual System

Significance: Glaucoma is an age-related neurodegenerative disorder of the visual system associated with sensitivity to intraocular pressure (IOP). It is the leading irreversible cause of vision loss worldwide, and vision loss results from damage and dysfunction of the retinal output neurons known as retinal ganglion cells (RGCs). Recent Advances: Elevated IOP and optic nerve injury triggers pruning of RGC dendrites, altered morphology of excitatory inputs from presynaptic bipolar cells, and disrupted RGC synaptic function. Less is known about RGC outputs, although evidence to date indicates that glaucoma is associated with altered mitochondrial and synaptic structure and function in RGC-projection targets in the brain. These early functional changes likely contribute to vision loss and might be a window into early diagnosis and treatment. Critical Issues: Glaucoma affects different RGC populations to varying extents and along distinct time courses. The influence of glaucoma on RGC synaptic function as well as the mechanisms underlying these effects remain to be determined. Since RGCs are an especially energetically demanding population of neurons, altered intracellular axon transport of mitochondria and mitochondrial function might contribute to RGC synaptic dysfunction in the retina and brain as well as RGC vulnerability in glaucoma. Future Directions: The mechanisms underlying differential RGC vulnerability remain to be determined. Moreover, the timing and mechanisms of RGCs synaptic dysfunction and degeneration will provide valuable insight into the disease process in glaucoma. Future work will be able to capitalize on these findings to better design diagnostic and therapeutic approaches to detect disease and prevent vision loss. Antioxid. Redox Signal. 37, 842-861.

The p-ERG spatial acuity in the biomedical pig under physiological conditions

Pigs are becoming an important pre-clinical animal species for translational ophthalmology, due to similarities with humans in anatomical and physiological patterns. Different models of eye disorders have been proposed, and they are good candidates to assess biocompatibility/functionality of retinal prostheses. Electroretinography is a common tool allowing to gain information on retinal function, with several types of electroretinogram (ERG) been implemented including full field (ff-ERG), multifocal (mf-ERG) and pattern (p-ERG). p-ERG represents a valuable tool to monitor Retinal Ganglion Cells (RGCs) activity and can be used to calculate p-ERG spatial acuity. Unfortunately, scarce methodological data are available regarding recording/interpretation of p-ERG and retinal acuity in biomedical pigs yet enhancing knowledge regarding pig vision physiology will allow for more refined and responsible use of such species. Aim of this study was to record p-ERG in juvenile pigs to functionally assess visual acuity. Six female hybrid pigs underwent two p-ERG recording sessions at 16 and 19 weeks of age. Photopic ff-ERG were also recorded; optical coherence tomography (OCT) and histology were used to confirm retinal integrity. ff-ERG signals were repeatable within/across sessions. All p-ERG traces consistently displayed characterizing peaks, and the progressive decrease of amplitude in response to the increment of spatial frequency revealed the reliability of the method. Mean p-ERG spatial acuities were 5.7 ± 0.14 (16 weeks) and 6.2 ± 0.15 cpd (19 weeks). Overall, the p-ERG recordings described in the present work seem reliable and repeatable, and may represent an important tool when it comes to vision assessment in pigs.

Restoration of mitochondria axonal transport by adaptor Disc1 supplementation prevents neurodegeneration and rescues visual function

Deficits in mitochondrial transport are a common feature of neurodegenerative diseases. We investigated whether loss of components of the mitochondrial transport machinery impinge directly on metabolic stress, neuronal death, and circuit dysfunction. Using multiphoton microscope live imaging, we showed that ocular hypertension, a major risk factor in glaucoma, disrupts mitochondria anterograde axonal transport leading to energy decline in vulnerable neurons. Gene- and protein-expression analysis revealed loss of the adaptor disrupted in schizophrenia 1 (Disc1) in retinal neurons subjected to high intraocular pressure. Disc1 gene delivery was sufficient to rescue anterograde transport and replenish axonal mitochondria. A genetically encoded ATP sensor combined with longitudinal live imaging showed that Disc1 supplementation increased ATP production in stressed neurons. Disc1 gene therapy promotes neuronal survival, reverses abnormal single-cell calcium dynamics, and restores visual responses. Our study demonstrates that enhancing anterograde mitochondrial transport is an effective strategy to alleviate metabolic stress and neurodegeneration.

Intereye structure-function relationship using photopic negative response in patients with glaucoma or glaucoma suspect

We evaluated the intereye structure–function relationship in glaucoma patients using photopic negative response in electroretinogram analysis. Patients with confirmed glaucoma (36 eyes, 36 patients) or suspected glaucoma (19 eyes, 19 patients) were included in this study. Electroretinogram (RETI-scan) was performed with red stimulus on blue background. Intereye comparison for 55 patients was performed between better eyes and worse eyes, which were divided based on average retinal nerve fiber layer (RNFL) thickness measured using spectral-domain optical coherence tomography. In the intereye analysis, PhNR amplitude was lower in worse eyes than in better eyes (P < 0.001). The intereye difference in PhNR amplitude was significantly correlated with intereye difference in average RNFL, as well as average or minimum ganglion cell-inner plexiform layer (GCIPL) thickness (P = 0.006, 0.044, 0.001). In patients with mean deviation ≥ − 6 dB of worse eyes, the intereye difference in PhNR amplitude was significantly associated with intereye difference in average RNFL thickness or minimum GCIPL thickness (P = 0.037, 0.007), but significant correlation was not found between mean sensitivity of visual field tests and structural parameters. In conclusion, PhNR performed well with regard to intereye structure–function association in glaucoma patients, especially at the early stage.

The thickness of the outer retina in the macula and circumpapillary area in patients with unilateral advanced glaucoma

PURPOSE

To compare outer macular and retinal thickness in the circumpapillary area in unilateral advanced glaucomatous eyes to the normal or mild glaucomatous fellow eyes.

METHODS

Seventy-eight eyes of 39 patients with unilateral advanced glaucoma (mean deviation (MD) worse than -12.00 dB based on visual field 24-2) were included in this cross-sectional study as the cases. The healthy or mild glaucomatous fellow eyes were enrolled as the control group. All eyes underwent optical coherence tomography of the macula and circumpapillary retina by Topcon DRI Triton (Topcon, Tokyo, Japan). Ganglion cell layer 2+ was considered as the inner retina. Total retinal thickness minus the thickness of the inner retina was considered as the outer retina. Comparison between groups was done by paired-sample sign test. The correlation between structural and functional parameters was evaluated by a partial correlation coefficient.

RESULTS

Seventeen (43.6%), 15 (38.5%), and 7 (17.9%) patients had pseudoexfoliation, primary angle-closure, and primary open-angle glaucoma, respectively. The mean age was 62.69 ± 12.00 years. Thirty-three (84.6%) patients were male. The outer retinal thickness in the circumpapillary area was higher in temporal, superior, and inferior quadrants (p < 0.05). The outer macula in different parafoveal and perifoveal quadrants was also thicker (p < 0.05). Average outer parafoveal thickness in the case group had a significant negative correlation with MD (r = -0.339; p = 0.035).

CONCLUSION

Advanced glaucomatous eyes had a thicker outer retina in the macula and circumpapillary area. There was a significant negative correlation between outer perifoveal thickness and MD.

Roles of Fatty Acids in Microglial Polarization: Evidence from In Vitro and In Vivo Studies on Neurodegenerative Diseases

Microglial polarization to the M1 phenotype (classically activated) or the M2 phenotype (alternatively activated) is critical in determining the fate of immune responses in neurodegenerative diseases (NDs). M1 macrophages contribute to neurotoxicity, neuronal and synaptic damage, and oxidative stress and are the first line of defense, and M2 macrophages elicit an anti-inflammatory response to regulate neuroinflammation, clear cell debris, and promote neuroregeneration. Various studies have focused on the ability of natural compounds to promote microglial polarization from the M1 phenotype to the M2 phenotype in several diseases, including NDs. However, studies on the roles of fatty acids in microglial polarization and their implications in NDs are a rare find. Most of the studies support the role of polyunsaturated fatty acids (PUFAs) in microglial polarization using cell and animal models. Thus, we aimed to collect data and provide a narrative account of microglial types, markers, and studies pertaining to fatty acids, particularly PUFAs, on microglial polarization and their neuroprotective effects. The involvement of only PUFAs in the chosen topic necessitates more in-depth research into the role of unexplored fatty acids in microglial polarization and their mechanistic implications. The review also highlights limitations and future challenges.

Frequency Doubling Technology Visual Field Loss in Fabry Subjects Related to Retinal Ganglion Cell Function as Explored by ERG and OSOME

Purpose

This study aims to evaluate potential causes of FDT visual field loss in a selected group of Fabry subjects.

Patients and Methods

This is a pilot observational study. Subjects were assessed during 2 visits. The following tests were performed: visual acuity, tonometry, optical coherence tomography (OCT) optic nerve scan, frequency doubling time (FDT) and threshold (SAP) VF, ERG, and Online Spectro-reflectometry Oxygenation Measurement in the Eye (OSOME). Results are compared across visits and, when indicated, interpreted against those collected on non-Fabry population matched for age and sex.

Results

The study population was composed of 3 males (34.3 ± 8.9 y.o.) and 5 females (46.4 ± 6.5 y.o). For all subjects, BCVA remained 6/6 OU throughout the study and OCT optic nerve scans were normal. FDT showed a defect in at least 1 quadrant for all participants, in contrast with SAP. FDT PSD value was found different vs SAP. For ERG, the i-wave (52.1 + 2.7 ms) and B-waves (31.6 ± 2.1 ms) peak times were significantly longer compared to a non-Fabry population (p < 0.05). Overall blood oxygenation varied from 61.3% ± 4% to 68.1% ± 4% at the second visit, suggesting a loss of capillary perfusion. Blood volume varied based on location (superior/inferior), eye tested (OD/OS) and time (visit 1/2). The range of values exceeds normal subjects findings (p < 0.05). Blood volume was correlated to FDT PSD value for the superior area of the optic nerve.

Conclusion

The results suggest that Fabry subjects present FDT deficits and abnormal ERG patterns that may be explained by a retinal dysfunction affecting retinal ganglion cells (RGCs), second to vascular alterations.

Multifocal Electroretinogram Photopic Negative Response: A Reliable Paradigm to Detect Localized Retinal Ganglion Cells' Impairment in Retrobulbar Optic Neuritis Due to Multiple Sclerosis as a Model of Retinal Neurodegeneration

The measure of the full-field photopic negative response (ff-PhNR) of light-adapted full-field electroretinogram (ff-ERG) allows to evaluate the function of the innermost retinal layers (IRL) containing primarily retinal ganglion cells (RGCs) and other non-neuronal elements of the entire retina. The aim of this study was to acquire functional information of localized IRL by measuring the PhNR in response to multifocal stimuli (mfPhNR). In this case-control observational and retrospective study, we assessed mfPhNR responses from 25 healthy controls and from 20 patients with multiple sclerosis with previous history of optic neuritis (MS-ON), with full recovery of visual acuity, IRL morphological impairment, and absence of morpho-functional involvement of outer retinal layers (ORL). MfPhNR response amplitude densities (RADs) were measured from concentric rings (R) with increasing foveal eccentricity: 0−5° (R1), 5−10° (R2), 10−15° (R3), 15−20° (R4), and 20−25° (R5) from retinal sectors (superior-temporal (ST), superior-nasal (SN), inferior-nasal (IN), and inferior-temporal (IT)); between 5° and 20° and from retinal sectors (superior (S), temporal (T), inferior (I), and nasal (N)); and within 5° to 10° and within 10° and 20° from the fovea. The mfPhNR RAD values observed in all rings or sectors in MS-ON eyes were significantly reduced (p < 0.01) with respect to control ones. Our results suggest that mfPhNR recordings may detect localized IRL dysfunction in the pathologic condition of selective RGCs neurodegeneration.

Novel Machine-Learning Based Framework Using Electroretinography Data for the Detection of Early-Stage Glaucoma

Purpose

Early-stage glaucoma diagnosis has been a challenging problem in ophthalmology. The current state-of-the-art glaucoma diagnosis techniques do not completely leverage the functional measures' such as electroretinogram's immense potential; instead, focus is on structural measures like optical coherence tomography. The current study aims to take a foundational step toward the development of a novel and reliable predictive framework for early detection of glaucoma using machine-learning-based algorithm capable of leveraging medically relevant information that ERG signals contain.

Methods

ERG signals from 60 eyes of DBA/2 mice were grouped for binary classification based on age. The signals were also grouped based on intraocular pressure (IOP) for multiclass classification. Statistical and wavelet-based features were engineered and extracted. Important predictors (ERG tests and features) were determined, and the performance of five machine learning-based methods were evaluated.

Results

Random forest (bagged trees) ensemble classifier provided the best performance in both binary and multiclass classification of ERG signals. An accuracy of 91.7 and 80% was achieved for binary and multiclass classification, respectively, suggesting that machine-learning-based models can detect subtle changes in ERG signals if trained using advanced features such as those based on wavelet analyses.

Conclusions

The present study describes a novel, machine-learning-based method to analyze ERG signals providing additional information that may be used to detect early-stage glaucoma. Based on promising performance metrics obtained using the proposed machine-learning-based framework leveraging an established ERG data set, we conclude that the novel framework allows for detection of functional deficits of early/various stages of glaucoma in mice.

Inhibition of p66Shc attenuates retinal ischemia-reperfusion injury-induced damage by activating the akt pathway

Retinal ganglion cell (RGC) death is the direct cause of several optic neuropathies. Several studies have reported that the loss of p66Shc ameliorates neuronal injury and vascular abnormalities in ischemia-reperfusion (I/R) injury. However, whether p66Shc is involved in the loss of RGC remains unclear. Therefore, this study aimed to investigate the function of p66Shc due to retinal ischemia in mice. The retinal I/R model was constructed after an intravitreal injection of recombinant adeno-associated viruses (rAAV-EGFP or rAAV-p66Shc-EGFP) for 4 weeks. The expression of p66Shc was detected by western blotting, quantitative real-time polymerase chain reaction, and immunofluorescence staining. The survival of RGCs was determined using immunofluorescence staining. Retinal function was analyzed based on electroretinogram (ERG) findings. Retinal cell apoptosis was detected by TdT-mediated dUTP nick-end labeling staining. The protein expressions of Akt, phospho-Akt, Bax, and PARP were analyzed by western blotting. After rAAVs were successfully transfected, enhanced green fluorescent protein was expressed in all retinal cell layers, and the level of p66Shc after I/R injury was successfully reduced. We found that inhibition of p66Shc expression remarkably decreased the death of RGCs and prevented the loss of ERG a- and b-wave amplitudes caused by retinal ischemia. Mechanistically, downregulation of p66Shc resulted in reduced Bax, whereas increased phospho-Akt and PARP. Taken together, our study revealed that p66Shc acts through the Akt pathway to protect RGCs from retinal I/R injury-induced apoptosis and retinal dysfunction, making p66Shc a possible therapeutic target for glaucoma treatment.

Macular Blood Flow and Pattern Electroretinogram in Normal Tension Glaucoma

Purpose: To investigate whether macular vessel density (VD) was associated with the pattern electroretinogram (PERG) in normal tension glaucoma (NTG). Design: Cross-sectional study. Methods: Seventy-six eyes from patients with NTG were included in this study. Macular VD was calculated from the superficial retinal layer, including the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL), using the built-in software provided with the optical coherence tomography angiography (OCTA) device. Functional parameters were obtained from standard automated perimetry (SAP) and PERG, using a commercial ERG stimulator. Moreover, structural parameters, such as peripapillary RNFL and macular ganglion cell/inner plexiform layer (GCIPL) thickness, were measured using OCT. Results: Patients with higher VD had higher N95 amplitude (p = 0.048). Macular VD was significantly correlated with N95 amplitude, irrespective of disease severity (r = 0.352, p = 0.002 for the total subjects and r = 0.276, p = 0.043 for mild glaucoma). According to regression analyses, N95 amplitude and macular VD were bidirectional significant factors (p = 0.035 and 0.019, respectively). For patients with mild to moderate glaucoma, N95 amplitude and macular VD were also significantly associated bidirectionally, according to regression analyses (p = 0.032 and 0.040, respectively). Conclusions: Macular VD was significantly associated with N95 amplitude from PERG. The correlation was prominent in early glaucoma, in contrast to the other structural or functional parameters. When considering that PERG represents the objective function of the retinal ganglion cell (RGC), macular VD was associated with RGC dysfunction before the functional change became apparent on SAP.

An optimized procedure to record visual evoked potential in mice

Visual evoked potential (VEP) is commonly used to evaluate visual acuity in both clinical and basic studies. Subdermal needle electrodes or skull pre-implanted screw electrodes are usually used to record VEP in rodents. However, the VEP amplitudes recorded by the former are small while the latter may damage the brain. In this study, we established a new invasive procedure for VEP recording, and made a series of comparisons of VEP parameters recorded from different electrode locations, different times of day (day and night) and bilateral eyes, to evaluate the influence of these factors on VEP in mice. Our data reveal that our invasive method is reliable and can record VEP with good waveforms and large amplitudes. The comparison data show that VEP is greatly influenced by active electrode locations and difference between day and night. In C57 or CD1 ONC (optic nerve crush) models and Brn3b^AP/AP mice, which are featured by loss of retinal ganglion cells (RGCs), amplitudes of VEP N1 and P1 waves are drastically reduced. The newly established VEP procedure is very reliable and stable, and is particularly useful for detecting losses of RGC quantities, functions or connections to the brain. Our analyses of various recording conditions also provide useful references for future studies.

Visual function tests for glaucoma practice - What is relevant?

Glaucoma represents one of the most important ocular diseases causing irreversible ganglion cell death. It is one of the most common causes of visual impairment and morbidity in the elderly population. There are various tests for measuring visual function in glaucoma. While visual field remains the undisputed method for screening, diagnosis, and monitoring disease progression, other tests have been studied for their utility in glaucoma practice. This review discusses some of the commonly used tests of visual function that can be routinely used in clinics for glaucoma management. Among the various modalities of testing visual function in glaucoma, this review highlights the tests that are most clinically relevant.

Steady-State Pattern Electroretinography in Eyes with Glaucoma and High Myopia

Purpose

To investigate features of the steady-state pattern electroretinogram (ssPERG) in subjects with glaucoma (G), high myopia (HM; spherical equivalent ≤-6D) and glaucoma with high myopia (GHM).

Patients and Methods

Our study included 48 participants divided into 3 groups (G, HM, and GHM) who each underwent monocular ssPERG testing with Diopsys NOVA PERG protocols. The ConStim protocol detects distinct topographic patterns of dysfunction 16° and 24° around the central macula. MagD is the amplitude of the average signal and MagD/Mag ratio indicates the consistency of the response. ssPERG indices were compared between groups and correlated with functional (ie, visual field mean deviation (VFMD)) and structural (ie, average retinal nerve fibre layer (RNFL) thickness; Cirrus optical coherence tomography) features.

Results

Participants had an average age of 59.4±7.6 years. Mean Humphrey VFMD was -14.22 ± 2.88dB, -2.62 ± 1.18dB and -12.80 ± 2.60dB for G, HM and GHM groups, respectively. Mean RNFL thickness was 63.0 ± 8.20μm, 69.5 ± 15.7μm and 60.6 ± 5.0μm for G, HM and GHM groups, respectively. For the 24° setting, no significant differences were noted for any of the parameters. For the 16° setting, MagD was lower in the GHM group compared to the HM group (0.29µV vs 0.52µV; p = 0.02). Significant differences were noted for the MagD/Mag ratio between HM and G groups (0.58 vs 0.40; p = 0.02) and between HM and GHM groups (0.58 vs 0.35; p = 0.002). There were positive correlations between both MagD 16° and MagD/Mag ratio 16° with VFMD (correlation coefficient [r]=0.37, p = 0.009; and r = 0.44, p = 0.002, respectively) and RNFL (r = 0.43, p = 0.002; and r = 0.48, p = 0.001, respectively).

Conclusion

MagD/Mag ratio at 16° was significantly lower in glaucomatous eyes (with or without high myopia) compared to those with high myopia without glaucoma, suggesting that glaucoma has a distinct impact on MagD/Mag ratio at 16° irrespective of the presence of myopia.

TRPV4-induced Müller cell gliosis and TNF-α elevation-mediated retinal ganglion cell apoptosis in glaucomatous rats via JAK2/STAT3/NF-κB pathway

Background

Glaucoma, the leading cause of irreversible blindness worldwide, is a type of retinal disease characterized by the selective death of retinal ganglion cells (RGCs). However, the pathogenesis of glaucoma has not been fully elucidated. Transient receptor potential vanilloid 4 (TRPV4) is a pressure-sensitive and calcium-permeable cation channel. TRPV4 is widely distributed in the retina and its sustained activation leads to RGC death; indicating that TRPV4 may be a possible target for glaucoma treatment. Here, we investigated the effects of TRPV4 on RGC apoptosis in a rat model of chronic ocular hypertension (COH), then examined the mechanism underlying these effects.

Methods

The COH model was established by injection of micro-magnetic beads into the anterior chamber of adult male rats. The expression levels of TRPV4, glial fibrillary acidic protein, and inflammatory factors were assessed by immunohistochemistry and immunoblotting. RGC apoptosis and visual dysfunction were evaluated by TUNEL assay and photopic negative response. Functional expression of TRPV4 was examined by electrophysiology and calcium imaging. Real-time polymerase chain reaction and immunoblotting were employed to investigate the molecular mechanism underlying the effects of TRPV4 on tumor necrosis factor-α (TNF-α) release.

Results

We found that TRPV4 played an essential role in glaucoma, such that high levels of TRPV4 expression were associated with elevated intraocular pressure. Furthermore, TRPV4 activation was involved in glaucoma-induced RGC apoptosis and RGC-related reductions in visual function. Mechanistic investigation demonstrated that TRPV4 activation led to enhanced Müller cell gliosis and TNF-α release via the JAK2/STAT3/NF-kB pathway, while TRPV4 inhibition could reverse these effects. Finally, TRPV4 activation could lead to elevated expression of TNF receptor 1 in RGCs, while inhibition of TNF-α could reduce TRPV4-mediated RGC apoptosis.

Conclusions

TRPV4 activation induces Müller cell gliosis and TNF-α elevation via the JAK2/STAT3/NF-κB pathway, which may exacerbate RGC apoptosis in glaucoma; these results suggest that TRPV4 can serve as a therapeutic target in glaucoma treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02315-8.

Non-invasive electrophysiology in glaucoma, structure and function-a review

Glaucoma, its early diagnosis, and monitoring of interventions remain an ongoing challenge. We here review developments in functional assessment and its relation to morphology, evaluating recent insights in electrophysiology in glaucoma and highlighting how glaucoma research and diagnostics benefit from combined approaches of OCT and electrophysiological investigations. After concise overviews of OCT and non-invasive electrophysiology in glaucoma, we evaluate commonalities and complementarities of OCT and electrophysiology for our understanding of glaucoma. As a specific topic, the dynamic range (floor effects) of the various techniques is discussed.

Relationship between structural and functional changes in glaucomatous eyes: a multifocal electroretinogram study

Background

The nasal to temporal amplitudes ratio (N/T) of multifocal electroretinography (mfERG) scans measured within 5° of the macula can be used to detect glaucomatous change. The photopic negative response (PhNR) of mfERG elicited by a circular stimulus centered on the fovea was significantly reduced in eyes with glaucoma. The PhNR to B-wave ratio (PhNR/B) is the optimal measure of the PhNR. However, clinical superiority for evaluating glaucoma patients has not been determined between N/T and PhNR/B yet.

Methods

For morphological assessments, ganglion cell complex (GCC) in six regions and the average were measured by optical coherence tomography (OCT). For functional assessment, Humphrey visual fields (VF) with mean sensitivities (MT) and mfERG scans with parameters of N/T and the multifocal photopic negative response to B-wave ratio (mfPhNR/B) were measured. Sixty-nine eyes of 44 glaucoma patients were included and correlations between mfERG parameters and OCT or VF parameters were evaluated.

Results

The mean age of patients was 59.4 years. The mean deviation for all eyes obtained with the VF 30–2 and VF 10–2 was − 7.00 and − 6.31 dB, respectively. Significant correlations between GCC thickness or VF parameter and the N/T were found, especially in the inferior and inforotemporal retinal areas corresponding to superior and superonasal VF sectors (GCC vs N/T; coefficient = − 7.916 and − 7.857, and MT vs N/T; coefficient = − 4.302 and − 4.437, in the inferior and inforotemporal retinal areas, respectively, all p values < 0.05). However, similar associations were not obtained between mfPhNR/B and OCT or VF parameters. The mfPhNR/B only in the inferotemporal sector was significantly correlated with the average thickness of GCC (coefficient = 4.823, P = 0.012).

Conclusions

The N/T was correlated with GCC and VF in more numbers of measurement areas than the mfPhNR/B in the current study, however, a future study modifying the stimuli and amplitudes to obtain the spatial correspondence to OCT and VF measurement will be required to evaluate the value of mfERG.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-02061-8.

Early Functional Impairment in Experimental Glaucoma Is Accompanied by Disruption of the GABAergic System and Inceptive Neuroinflammation

Glaucoma is a leading cause of irreversible blindness worldwide, and increased intraocular pressure (IOP) is a major risk factor. We aimed to determine if early functional and molecular differences in the glaucomatous retina manifest before significant retinal ganglion cell (RGC) loss is apparent. Adenoviral vectors expressing a pathogenic form of myocilin (Ad5.MYOC) were used to induce IOP elevation in C57BL/6 mice. IOP and pattern electroretinograms (pERG) were recorded, and retinas were prepared for RNA sequencing, immunohistochemistry, or to determine RGC loss. Ocular injection of Ad5.MYOC leads to reliable IOP elevation, resulting in significant loss of RGC after nine weeks. A significant decrease in the pERG amplitude was evident in eyes three weeks after IOP elevation. Retinal gene expression analysis revealed increased expression for 291 genes related to complement cascade, inflammation, and antigen presentation in hypertensive eyes. Decreased expression was found for 378 genes associated with the γ-aminobutyric acid (GABA)ergic and glutamatergic systems and axon guidance. These data suggest that early functional changes in RGC might be due to reduced GABA_A receptor signaling and neuroinflammation that precedes RGC loss in this glaucoma model. These initial changes may offer new targets for early detection of glaucoma and the development of new interventions.

AMPK hyperactivation promotes dendrite retraction, synaptic loss, and neuronal dysfunction in glaucoma

BACKGROUND

The maintenance of complex dendritic arbors and synaptic transmission are processes that require a substantial amount of energy. Bioenergetic decline is a prominent feature of chronic neurodegenerative diseases, yet the signaling mechanisms that link energy stress with neuronal dysfunction are poorly understood. Recent work has implicated energy deficits in glaucoma, and retinal ganglion cell (RGC) dendritic pathology and synapse disassembly are key features of ocular hypertension damage.

RESULTS

We show that adenosine monophosphate-activated protein kinase (AMPK), a conserved energy biosensor, is strongly activated in RGC from mice with ocular hypertension and patients with primary open angle glaucoma. Our data demonstrate that AMPK triggers RGC dendrite retraction and synapse elimination. We show that the harmful effect of AMPK is exerted through inhibition of the mammalian target of rapamycin complex 1 (mTORC1). Attenuation of AMPK activity restores mTORC1 function and rescues dendrites and synaptic contacts. Strikingly, AMPK depletion promotes recovery of light-evoked retinal responses, improves axonal transport, and extends RGC survival.

CONCLUSIONS

This study identifies AMPK as a critical nexus between bioenergetic decline and RGC dysfunction during pressure-induced stress, and highlights the importance of targeting energy homeostasis in glaucoma and other neurodegenerative diseases.

Pupillometric recordings to detect glaucoma

Objective. Glaucoma is the second cause of vision loss with early diagnosis having significantly better prognosis. We propose the use of hippus, the steady-state pupil oscillations, obtained from an eye-tracker for computerised detection of glaucoma.Approach. Pupillary data were recorded using a commercial eye-tracker device directly to the laptop. A total of 40 glaucoma patients and 30 age-matched controls were recruited for the study. The signals were de-noised, and the entropy of the steady-state oscillations was obtained for two light intensities, 34 and 100 cd m^-2.Main results. The results show that at 100 cd m^-2, there was significant difference (p < 0.05) between the sample entropy of the healthy eyes (0.55 ± 0.017) and glaucoma eyes (0.7 ± 0.034). The results at 34 cd m^-2were also significantly different, though to a lesser extent.Significance. Entropy of the pupillary oscillations, or hippus, obtained using an eye-tracking device showed a significant difference between glaucoma and healthy eyes. The method used commercially available inexpensive hardware and thus has the potential for wide-scale deployment for computerized detection of glaucoma.

Krüppel-like factor 7 protects retinal ganglion cells and promotes functional preservation via activating the Akt pathway after retinal ischemia-reperfusion injury

OBJECTIVE

The purpose of this study is to investigate the effects of Krüppel-like factor 7 (KLF7) on retinal ganglion cells (RGCs) and retinal function after retinal ischemia-reperfusion (RIR) injury in mice.

METHODS

Male C57BL/6J mice were intravitreally injected with recombinant adeno-associated vectors (rAAV-KLF7-EGFP or rAAV-EGFP), and subsequently used to induce RIR injury. Retinal cryosections were used to access the efficacy of virus transfection, 1, 2, 3, and 4 weeks after rAAV-KLF7-EGFP transfer. RGCs survival rate was observed and quantified by immunofluorescent staining, 7 days after RIR injury. Meanwhile, electroretinogram (ERG) and optomotor response were used to evaluate the electrophysiological functions and visual acuity. Apoptosis was evaluated by TUNEL staining 1 day after RIR injury. Expression of KLF7, Akt, phospho-Akt, Bcl-2, and Bax were further detected by western blot to excavate the underlying mechanism.

RESULTS

The transfection efficiency of rAAV-KLF7-EGFP was increased in a time-dependent manner, and the number of EGFP-positive cells was increased significantly 3 weeks after rAAV-KLF7-EGFP transfer. RGCs survival rates, amplitudes of ERG a-, b-wave, Ops, PhNR, and visual acuity of mice were decreased after RIR injury. With the increase of light intensity, the amplitudes of scotopic ERG a- and b-wave were gradually increased while the incubation period was gradually shortened. RGCs survival rates, amplitudes of ERG a-, b-wave, Ops, PhNR, and visual acuity of mice were increased after rAAV-KLF7-EGFP transfer. The protein level of KLF7 was up-regulated after rAAV-KLF7-EGFP transfer. Up-regulation of KLF7 significantly inhibited cells apoptosis, increased phospho-Akt and Bcl-2 expression, and decreased Bax expression. There were no significant changes in Akt expression.

CONCLUSION

Overexpression of KLF7 can not only prevent the loss of RGCs, but also preserve the electrophysiological function. In addition, overexpression of KLF7 can ameliorate the retinal dysfunction after RIR injury, and ultimately improve the visual acuity of mice. The activation of Akt pathway and the suppression of the mitochondrial apoptotic pathway contribute to the neuroprotection of KLF7.

Evaluating multidisciplinary glaucoma care: visual field progression and loss of sight year analysis in the community vs hospital setting

Background

A variety of shared care models have been developed, which aim to stratify glaucoma patients according to risk of disease progression. However, there is limited published data on the rate of glaucoma progression in the hospital vs community setting. Here we aimed to compare rates of glaucomatous visual field progression in the Cambridge Community Optometrist Glaucoma Scheme (COGS) and Addenbrooke’s Hospital Glaucoma Clinic (AGC).

Methods

A retrospective comparative cohort review was performed. Patients with five or more visual field tests were included. Zeiss Forum software was used to calculate the MD progression rate (dB/year). Loss of sight years (LSY) were also calculated for both COGS and AGC.

Results

Overall, 8465 visual field tests from 854 patients were reviewed. In all, 362 eyes from the AGC group and 210 eyes from COGS were included. The MD deterioration rate was significantly lower in the COGS patients compared with the AGC group (−0.1 vs −0.3 dB/year; p < 0.0001). No patients in the COGS group were predicted to become blind within their lifetime by LSY analysis. Fifteen patients were at risk in the AGC group.

Conclusion

This service evaluation shows that COGS is an effective scheme to stratify lower risk glaucoma patients, increasing the capacity within hospital eye services. COGS patients have a lower rate of visual field deterioration compared to AGC patients. Effective communication between community and tertiary schemes is essential to facilitate transfer of patients requiring further hospital management reliably and efficiently, with the potential for low-risk patients to be followed safely in the community.

Disruption of 24-Hour Rhythm in Intraocular Pressure Correlates with Retinal Ganglion Cell Loss in Glaucoma

Parameters of 24-h rhythm in intraocular pressure (IOP) were assessed in patients with stable or advanced primary open-angle glaucoma (S-POAG/A-POAG) and referenced to the phase of “marker” circadian temperature rhythm of each patient. Body temperature and IOP were measured over a 72-h span in 115 participants (65 S-POAG and 50 A-POAG). Retinal Ganglion Cell (RGC) damage was assessed by high-definition optical coherence tomography. The 24-h IOP rhythm in A-POAG patients peaked during the night, opposite to the daytime phase position in S-POAG patients (p < 0.0001). The 24-h IOP phase correlated with RGC loss (p < 0.0001). The internal phase shift between IOP and body temperature gradually increased with POAG progression (p < 0.001). Angiotensin converting enzyme Alu-repeat deletion/insertion (ACE I/D) emerged as a candidate gene polymorphism, which may play a role in the alteration of the circadian IOP variability in advanced glaucoma. To conclude, a reliable estimation of the 24-h rhythm in IOP requires the degree of RGC damage to be assessed. In advanced POAG, the 24-h phase of IOP tended to occur during the night and correlated with RGC loss, being progressively delayed relative to the phase of temperature.

A Topical Formulation of Melatoninergic Compounds Exerts Strong Hypotensive and Neuroprotective Effects in a Rat Model of Hypertensive Glaucoma

Melatonin is of great importance for regulating several eye processes, including pressure homeostasis. Melatonin in combination with agomelatine has been recently reported to reduce intraocular pressure (IOP) with higher efficacy than each compound alone. Here, we used the methylcellulose (MCE) rat model of hypertensive glaucoma, an optic neuropathy characterized by the apoptotic death of retinal ganglion cells (RGCs), to evaluate the hypotensive and neuroprotective efficacy of an eye drop nanomicellar formulation containing melatonin/agomelatine. Eye tissue distribution of melatonin/agomelatine in healthy rats was evaluated by HPLC/MS/MS. In the MCE model, we assessed by tonometry the hypotensive efficacy of melatonin/agomelatine. Neuroprotection was revealed by electroretinography; by levels of inflammatory and apoptotic markers; and by RGC density. The effects of melatonin/agomelatine were compared with those of timolol (a beta blocker with prevalent hypotensive activity) or brimonidine (an alpha 2 adrenergic agonist with potential neuroprotective efficacy), two drugs commonly used to treat glaucoma. Both melatonin and agomelatine penetrate the posterior segment of the eye. In the MCE model, IOP elevation was drastically reduced by melatonin/agomelatine with higher efficacy than that of timolol or brimonidine. Concomitantly, gliosis-related inflammation and the Bax-associated apoptosis were partially prevented, thus leading to RGC survival and recovered retinal dysfunction. We suggest that topical melatoninergic compounds might be beneficial for ocular health.

Combined Multi-Modal Assessment of Glaucomatous Damage With Electroretinography and Optical Coherence Tomography/Angiography

Purpose

To compare the diagnostic performance and to evaluate the interrelationship of electroretinographical and structural and vascular measures in glaucoma.

Methods

For 14 eyes of 14 healthy controls and 15 eyes of 12 patients with glaucoma ranging from preperimetric to advanced stages optical coherence tomography (OCT), OCT-angiography (OCT-A), and electrophysiological measures (multifocal photopic negative response ratio [mfPhNR] and steady-state pattern electroretinography [ssPERG]) were applied to assess changes in retinal structure, microvasculature, and function, respectively. The diagnostic performance was assessed via area-under-curve (AUC) measures obtained from receiver operating characteristics analyses. The interrelation of the different measures was assessed with correlation analyses.

Results

The mfPhNR, ssPERG amplitude, parafoveal (pfVD) and peripapillary vessel density (pVD), macular ganglion cell inner plexiform layer thickness (mGCIPL) and peripapillary retinal nerve fiber layer thickness (pRNFL) were significantly reduced in glaucoma. The AUC for mfPhNR was highest among diagnostic modalities (AUC: 0.88, 95% confidence interval: 0.75-1.0, P < 0.001), albeit not statistically different from that for macular (mGCIPL: 0.76, 0.58-0.94, P < 0.05; pfVD: 0.81, 0.65-0.97, P < 0.01) or peripapillary imaging (pRNFL: 0.85, 0.70-1.0, P < 0.01; pVD: 0.82, 0.68-0.97, P < 0.01). Combined functional/vascular measures yielded the highest AUC (mfPhNR-pfVD: 0.94, 0.85-1.0, P < 0.001). The functional/structural measure correlation (mfPhNR-mGCIPL correlation coefficient [rs]: 0.58, P = 0.001; mfPhNR-pRNFL rs: 0.66, P < 0.001) was stronger than the functional-vascular correlation (mfPhNR-pfVD rs: 0.29, P = 0.13; mfPhNR-pVD rs: 0.54, P = 0.003).

Conclusions

The combination of ERG measures and OCT-A improved diagnostic performance and enhanced understanding of pathophysiology in glaucoma.

Translational Relevance

Multimodal assessment of glaucoma damage improves diagnostics and monitoring of disease progression.

Probing ON and OFF Retinal Pathways in Glaucoma Using Electroretinography

Glaucoma is a progressive neurodegenerative disease involving damage and eventually death of retinal ganglion cells (RGCs) that comprise the optic nerve. This review summarizes current understanding of specific RGC type vulnerability in glaucoma and how electroretinography (ERG) may provide an objective measure of these functional perturbations. There is building evidence to suggest that ON RGCs, which respond to light increments, may be more resilient to elevated intraocular pressure and glaucoma, whereas OFF RGCs, which respond to light decrements, may be more susceptible. ERG experiments in nonhuman primates and mice have also shown that the ON- and OFF-pathways can be separated using a variety of techniques such as pattern ERG and the photopic negative response. Another ERG paradigm of interest to separate the ON and OFF responses is a flicker stimulus at varying temporal frequencies. Response to lower temporal frequencies is associated with the ON-pathway, and ERG response to higher frequencies is associated with the OFF-pathway. In mice, experimental glaucoma models have shown greater decreases in ERG response at higher frequencies, suggesting that the OFF-pathway is more susceptible. We also summarize current clinical ERG protocols used for glaucoma and discuss innovations for developing new types of stimuli that can further separate the ON- and OFF-pathways. Applying these novel paradigms that distinguish ON- and OFF-pathways may ultimately improve glaucoma diagnostics and monitoring of glaucoma progression.

Short-Term Steady-State Pattern Electroretinography Changes Using a Multi-Pressure Dial in Ocular Hypertensive, Glaucoma Suspect, and Mild Open-Angle Glaucoma Patients: A Randomized, Controlled, Prospective, Pilot Study

Introduction

This study evaluates the effects of the multi-pressure dial (MPD) on steady-state pattern electroretinography (ss-pERG) parameters. The study is a randomized, controlled, prospective, pilot trial in a private practice setting with ocular hypertensive (OHT), glaucoma suspect, and open-angle glaucoma (OAG) subjects.

Methods

This study included nine patients (64 ± 9.0 years, nine female) with OHT, glaucoma suspect, or mild OAG. One eye of each subject was randomized to receive negative periocular pressure, while the contralateral eye served as the intrasubject control through the goggle without negative pressure. The Diopsys High Contrast Sensitivity ss-pERG protocol was conducted on both eyes of each subject while wearing the MPD device. Application of negative periocular pressure was set at 50% of baseline intraocular pressure for each study eye.

Results

Following 2 h of negative periocular pressure application, the difference in MagnitudeD (MagD) from baseline for eyes randomized to receive negative periocular pressure (+ 0.17 versus  − 0.26) was statistically significant (p = 0.023). Over the same period, the change in MagD/Magnitude (MagD/Mag ratio) from baseline for eyes randomized to receive negative periocular pressure was also higher (+ 0.14 versus  − 0.16), compared to the control eyes, approached significance (p = 0.059).

Conclusions

Following 2 h of MPD wear, the measured MagD and MagD/Mag ratio improved compared to control, suggesting that negative periocular pressure application to the anterior globe can lead to short-term improvement in one measure of retinal ganglion cell function.

Electrophysiology in Glaucoma

OBJECTIVES

Electrophysiological testing of the visual system has been continuously used in studies involving the evaluation of retinal ganglion cells and the diagnosis of glaucoma. This study aims to review the results of recent studies regarding the clinical applicability of electrophysiological tests to glaucoma.

METHODS

A systematic review of the literature was carried out by 2 independent reviewers using the PubMed and EMBASE electronic databases, searching for articles published in English from January 1, 2014 to July 1, 2019 using a combination of the following keywords: ("glaucoma" OR "ocular hypertension") AND ("electrophysiolog" OR "electroretinogra" OR "ERG" OR "mfERG" OR "Pattern-reversal electroretinography" OR "PERG" OR "mfPERG" OR "photopic negative response" OR "pattern electroretinogram" OR "visual evoked potential" OR "multifocal electroretinography" OR "multifocal electroretinogram" OR "electro-oculography" OR "multifocal VEP" OR "mf-ERG"). A total of 38 studies were selected and the data of 30 of them were tabulated in this review.

RESULTS

Among the 30 studies selected, the photopic negative response and the reversal pattern electroretinogram were found to be the major methods used to record the electroretinographic responses generated by the retinal ganglion cell. Their multifocal versions and the multifocal visual evoked potential were also proposed during this period. In general, the results underscored a consistent but general correlation between the amplitude and latency measures and routine tests for glaucoma, such as perimetry and optical coherence tomography.

DISCUSSION

In agreement with previous reviews, clinical electrophysiological testing of the visual system reasonably matched with both the structural and functional analyses for glaucoma. No definitive indications of these tests have been established either at early detection or during follow-up of the disease, and easier protocols and better topographical correspondence with current glaucoma tests are warranted for their routine use.

Long-term PERG monitoring of untreated and treated glaucoma suspects

PURPOSE

To investigate long-term structural and functional progression of untreated and treated glaucoma suspects (UGS and TGS).

METHODS

Retrospective analysis of serial steady-state pattern electroretinogram (PERG), mean retinal nerve fiber layer thickness (RNFLT), and standard automated perimetry mean deviation (SAP-MD) in UGS (N = 20) and TGS (N = 18). Outcome measures were the rates of change (linear regression slopes) of PERG amplitude, PERG phase, mean RNFLT, and SAP-MD over 9.8 ± 1.3 years (15.6 ± 4.2 visits).

RESULTS

The number of patients with significant (P < 0.05) progression slopes for PERG amplitude, PERG phase, RNFLT, and SAP-MD was, respectively, UGS: 5, 0, 4, 2; TGS: 8, 2, 6, 5. In UGS, outcome measures were not correlated with each other. In TGS, both PERG amplitude and RNFLT were significantly (P < 0.05) correlated with SAP-MD (R ≥ 0.58), while PERG amplitude and RNFLT were not correlated with each other (R = 0.43, P = 0.064). The rate of change of SAP-MD was predicted (P < 0.05) by a linear combination of RNFLT slope and PERG amplitude slope.

CONCLUSIONS

Results substantiate and extend previous results showing that steady-state PERG amplitude progressively decreased over time in a proportion of glaucoma suspects, with relatively steeper slope in TGS compared to UGS. RNFLT progression also had a steeper slope in TGS compared to UGS; however, progressions of PERG amplitude and RNFLT were not significantly correlated. Both PERG progression and RNFLT progression independently contribute to prediction of visual field progression.

XEN Gel Stent in the management of primary open-angle glaucoma

Purpose

To assess the efficacy and safety of the XEN Gel Stent in patients with primary open-angle glaucoma.

Materials and methods

Twenty eyes of 17 patients (6 males, 11 females) with primary open-angle glaucoma were implanted with XEN Gel Stent. The following data were ascertained in each participant at baseline and at 1, 3, 6, 9 and 12 months following implanting procedure: intraocular pressure, number of anti-glaucoma medications, retinal sensitivity (PS 24/2 w/w), pattern electroretinogram (ISCEV standard), as well as the number of complications.

Results

The mean intraocular pressure reduction in a 1-year follow-up was 18% (21.56 vs. 17.69 mmHg, p < 0.001). The mean number of anti-glaucoma medications was reduced from 3.2 to 1.6 (p = 0.001). The PERG parameters at baseline and at 12 months postoperatively included a stable amplitude of P50 (2.55 µV vs. 2.65 µV, p = 0.024) and N95 (3.45 µV vs. 3.38 µV, p = ns) waves. The delta N95 and delta P50 amplitudes remained stable over the follow-up period (p = ns). The mean deviation (MD) of PS 24/2 was − 6.54 dB vs. − 8.43 dB, p = ns, whereas the pattern standard deviation (PSD) was 6.18 dB vs. 6.91 dB, p = ns. Transient hypotony within the first postoperative week occurred in 18 eyes (90%), whereas hyphema occurred in two eyes (10%). Needle revision of a filtration bleb was performed in five eyes (25%).

Conclusions

The XEN Gel Stent enables significant reduction in intraocular pressure with very low complication rates. It ensures a stabilization of the retinal function as established with the PERG.

Empirical Mode Decomposition-Based Filter Applied to Multifocal Electroretinograms in Multiple Sclerosis Diagnosis

As multiple sclerosis (MS) usually affects the visual pathway, visual electrophysiological tests can be used to diagnose it. The objective of this paper is to research methods for processing multifocal electroretinogram (mfERG) recordings to improve the capacity to diagnose MS. MfERG recordings from 15 early-stage MS patients without a history of optic neuritis and from 6 control subjects were examined. A normative database was built from the control subject signals. The mfERG recordings were filtered using empirical mode decomposition (EMD). The correlation with the signals in a normative database was used as the classification feature. Using EMD-based filtering and performance correlation, the mean area under the curve (AUC) value was 0.90. The greatest discriminant capacity was obtained in ring 4 and in the inferior nasal quadrant (AUC values of 0.96 and 0.94, respectively). Our results suggest that the combination of filtering mfERG recordings using EMD and calculating the correlation with a normative database would make mfERG waveform analysis applicable to assessment of multiple sclerosis in early-stage patients.

Protective Efficacy of a Dietary Supplement Based on Forskolin, Homotaurine, Spearmint Extract, and Group B Vitamins in a Mouse Model of Optic Nerve Injury

Glaucoma is a multifactorial blinding disease with a major inflammatory component ultimately leading to apoptotic retinal ganglion cell (RGC) death. Pharmacological treatments lowering intraocular pressure can help slow or prevent vision loss although the damage caused by glaucoma cannot be reversed. Recently, nutritional approaches have been evaluated for their efficacy in preventing degenerative events in the retina although mechanisms underlying their effectiveness remain to be elucidated. Here, we evaluated the efficacy of a diet supplement consisting of forskolin, homotaurine, spearmint extract, and vitamins of the B group in counteracting retinal dysfunction in a mouse model of optic nerve crush (ONC) used as an in vivo model of glaucoma. After demonstrating that ONC did not affect retinal vasculature by fluorescein angiography, we determined the effect of the diet supplement on the photopic negative response (PhNR) whose amplitude is strictly related to RGC integrity and is therefore drastically reduced in concomitance with RGC death. We found that the diet supplementation prevents the reduction of PhNR amplitude (p < 0.001) and concomitantly counteracts RGC death, as in supplemented mice, RGC number assessed immunohistochemically is significantly higher than that in non-supplemented animals (p < 0.01). Major determinants of the protective efficacy of the compound are due to a reduction of ONC-associated cytokine secretion leading to decreased levels of apoptotic markers that in supplemented mice are significantly lower than in non-supplemented animals (p < 0.001), ultimately causing RGC survival and ameliorated visual dysfunction. Overall, our data suggest that the above association of compounds plays a neuroprotective role in this mouse model of glaucoma thus offering a new perspective in inflammation-associated neurodegenerative diseases of the inner retina.

[Modern view on ocular hypertension]

Increased intraocular pressure is the main, and the only modifiable risk factor in the development of glaucoma. This review analyzes studies on differential diagnostics of ocular hypertension and risk factors of its conversion to glaucoma, and gives recommendations based on literature data for the most correct algorithm for management of patients with ocular hypertension.

Relationship between pattern electroretinogram and optic disc morphology in glaucoma

Purpose

To evaluate the relationship between pattern electroretinogram (PERG) and optic disc morphology in glaucoma suspect and glaucoma.

Methods

Eighty-six eyes of glaucoma suspect and 145 eyes of manifest glaucoma subjects were included in this study. Average peripapillary retinal nerve fiber layer (RNFL) thickness was obtained with spectral-domain optical coherence tomography, and optic disc imaging was performed using the Heidelberg Retinal Tomograph (HRT). Visual function was evaluated with perimetry (SITA and frequency doubling technology) and PERG. Scatter plots and correlation coefficients were evaluated between visual function and RNFL thickness or optic disc structure.

Results

Scatter plots of PERG and perimetry according to RNFL thickness change showed that PERG started to decrease earlier than did perimetry. The differences between linear and logarithmic R² were largest for the scatter plot of SITA 24–2 (linear R² = 0.415; logarithmic R² = 0.443) and the smallest for P50 amplitude of PERG (linear R² = 0.136, logarithmic R² = 0.138). In glaucoma suspect, HRT parameters such as cup shape measure (CSM) and linear cup-disc ratio (CDR) had significant correlations with PERG amplitudes (P = 0.016 for P50 and 0.049 for N95 in CSM, P = 0.012 for P50 in CDR). However, in glaucoma patients, mean RNFL thickness was associated with PERG amplitude (P = 0.011 for P50 and 0.002 for N95).

Conclusions

PERG deterioration occurred earlier than did perimetry according to RNFL thickness decrease. PERG amplitudes were significantly correlated with disc morphology in glaucoma suspect. These results suggest that PERG can detect ganglion cell dysfunction before the cells die.