The spatial distribution of ERGs reflecting luminance and L-/M-cone-opponent signals

PURPOSE

To study the spatial retinal distribution of electroretinographic (ERG) responses that reflect signals in the L-/M-cone-opponent and luminance post-receptoral pathways.

METHODS

ERG recordings to heterochromatic stimuli (sinusoidal counter-phase modulation of red and green LED light sources) were performed, while varying fractions of red and green modulation. Two temporal frequencies of the stimuli were employed: 12 Hz to record ERGs that reflect L-/M-cone-opponent signal and 36 Hz for recording ERG signals sensitive to stimulus luminance. Stimuli were about 20° in diameter and projected on various retinal locations: the fovea and four eccentricities (10°, 19°, 28° and 35°), each presented nasally, temporally, inferiorly and superiorly from the fovea.

RESULTS

The 36 Hz stimuli elicited responses that strongly varied with red fraction and were minimal at iso-luminance. Moreover, response phases changed abruptly at the minimum by 180°. In contrast, the responses to the 12 Hz stimuli had amplitudes and phases that changed more gradually with red fraction. The 36 Hz response amplitudes were maximal close to the fovea and sharply decreased with increasing distance from the fovea. The responses to 12 Hz stimuli were more broadly distributed across the retina.

CONCLUSIONS

In the present study, it was found that retinal eccentricity and direction from the fovea have distinct effects on ERGs reflecting different post-receptoral mechanisms. The results are in accord with previous findings that ERGs to 12 Hz stimuli are predominantly determined by the red-green chromatic content of the stimuli, thus reflecting activation in the L-/M-cone-opponent pathway, while responses to 36 Hz stimuli manifest post-receptoral luminance-dependent activation. We found that the response in the cone-opponent pathway is broadly comparable across the retina; in comparison, response amplitude of the luminance pathway strongly depends on retinal stimulus position.

Long-term full-field and multifocal electroretinographic changes after treatment with ranibizumab in patients with diabetic macular edema

PURPOSE

To investigate changes in macular and panretinal neuroretinal functions by electroretinographic examinations in eyes with diabetic macular edema (DME) treated with intravitreal ranibizumab.

MATERIAL AND METHODS

Sixty-four patients with DME were included in this prospective study. Patients were treated with ranibizumab injection according to the PRN regimen for over 12 months. Before treatment, all patients underwent fundus fluorescein angiography, optical coherence tomography (OCT), best-corrected visual acuity (BCVA) assessment, full-field (ff-ERG), and multifocal electroretinography (mf-ERG). In monthly visits, BCVA and OCT were performed. Besides, mf-ERG recordings were obtained at months 3, 6, 9, and 12, and ff-ERG was performed at month 12.

RESULTS

Fifty-eight patients completed the study. The mean age was 61.1 ± 8.5 (39-80) years. The mean number of injections was 6.19 ± 1.9. The decimal BCVA improved from 0.30 to 0.45 during the 12-month follow-up (p < 0.05). Macular thickness decreased from 413.5 μm to 329.5 μm (p < 0.05). The mf-ERG recordings in the central macular region showed improvements N1 and P1 amplitudes at months 9 and 12. There was a positive correlation between the baseline central (p < 001; r: - 0.378 and p < 0.05; r:-0.335, respectively), the second ring (p < 0.05; r: - 0.260 and p < 0.05; r: - 0.270, respectively) P1- and N1-wave amplitudes, and the BCVA at month 12. Full-field ERG recordings showed that peripheral neuroretinal responses were maintained or improved at month 12. Statistically significant improvements in BCVA and macular thickness were observed at all follow-up visits.

CONCLUSION

Multifocal electroretinographic recording started to improve 6 months after the beginning of intravitreal ranibizumab treatment in eyes with DME. This improvement was significant at months 9 and 12. A significant improvement in ff-ERG was observed at month 12.

SPOAN syndrome: a novel mutation and new ocular findings; a case report

Background

To report a novel mutation and new clinical findings in a case with SPOAN syndrome (spastic paraplegia, optic atrophy, neuropathy).

Case presentation

Clinical examination, genetic testing and electroretinography were used to study a 2-year-old child who was referred to our clinic with no visual attention and documented SPOAN syndrome. Fundoscopy revealed optic atrophy, diffuse retinal pigment mottling, severe vascular attenuation, and completely non-vascularized peripheral retina in both eyes. Full-field electroretinogram (ERG) revealed flat responses.

Conclusions

Severe retinopathy and flat full-field ERG responses can occur in SPOAN syndrome.

Human Dental Pulp Stem Cells (DPSCs) Therapy in Rescuing Photoreceptors and Establishing a Sodium Iodate-Induced Retinal Degeneration Rat Model

BACKGROUND

Different methods have been used to inject stem cells into the eye for research. We previously explored the intravitreal route. Here, we investigate the efficacy of intravenous and subretinal-transplanted human dental pulp stem cells (DPSCs) in rescuing the photoreceptors of a sodium iodate-induced retinal degeneration model.

METHODS

Three groups of Sprague Dawley rats were used: intervention, vehicle group and negative control groups (n = 6 in each). Intravenous injection of 60 mg/kg sodium iodate (day 0) induced retinal degeneration. On day 4 post-injection of sodium iodate, the rats in the intervention group received intravenous DPSC and subretinal DPSC in the right eye; rats in the vehicle group received subretinal Hank's balance salt solution and intravenous normal saline; while negative control group received nothing. Electroretinogram (ERG) was performed to assess the retinal function at day 0 (baseline), day 4, day 11, day 18, day 26, and day 32. By the end of the study at day 32, the rats were euthanized, and both their enucleated eyes were sent for histology.

RESULTS

No significant difference in maximal ERG a-wave (p = 0.107) and b-wave, (p = 0.153) amplitude was seen amongst the experimental groups. However, photopic 30 Hz flicker amplitude of the study eye showed significant differences in the 3 groups (p = 0.032). Within the intervention group, there was an improvement in 30 Hz flicker ERG response of all 6 treated right eyes, which was injected with subretinal DPSC; while the 30 Hz flicker ERG of the non-treated left eyes remained flat. Histology showed improved outer nuclear layer thickness in intervention group; however, findings were not significant compared to the negative and vehicle groups.

CONCLUSION

Combination of subretinal and intravenous injection of DPSCs may have potential to rescue cone function from a NaIO₃-induced retinal injury model.

Intravitreal ketamine promotes neuroprotection in rat eyes after experimental ischemia

Retinal ischemia, one of the most common cause of visual loss, is associated with blood flow inadequacy and subsequent tissue injury. In this setting, some treatments that can counteract glutamate increase, arouse interest in ischemic pathogenesis. Ketamine, a potent N-methyl-d-aspartate (NMDA) receptor antagonist, provides a neuroprotective pathway via decreasing the excitotoxicity triggered by excess glutamatergic. Thus, the goal of this study was to evaluate the safety of intravitreal use of ketamine and their potential protective effects on retinal cells in retinal ischemia/reperfusion model. Initially, ketamine toxicity was evaluated by cytotoxicity assay and Hen's egg chorioallantoic membrane (HET-CAM) method. Afterward, some ketamine concentrations were tested in rat's eyes to verify the safety of the intravitreal use. To investigate the neuroprotective effect on retinal, a single intravitreal injection of ketamine in concentrations of 0.059 mmol.L-1 and 0.118 mmol.L-1 was performed one day before the retinal injury by ischemia/reperfusion model. After 7 and 15 days, the retina activity was evaluated by electroretinogram (ERG) records and, lastly, by morphological analyzes. Cytotoxicity assay reveals that the maximum ketamine concentration that could reach retinal pigmented epithelium cells is 0.353 mmol.L-1. HET-CAM assay showed that concentrations above 0.237 mmol.L-1 are irritants to the eye. Thus, Ketamine in concentrations of 0.0237 mmol.L-1, 0.118 mmol.L-1, and 0.059 mmol.L-1 were selected for in vivo toxicity test. ERG records reveal a tendency of b-wave amplitude to decrease as the luminous intensity increased, in the group receiving ketamine at 0.237 mmol.L-1. Therefore, ketamine in concentrations at 0.059 mmol.L-1 and 0.118 mmol.L-1 were chosen for the following tests. In the ischemia retinal degeneration model, pretreatment with ketamine was capable to promote a recovery of retinal electrophysiological function minimizing the ischemic effects. In histological analysis, the groups that received intravitreal ketamine showed a number of retinal cells significantly higher than the vehicle group. In TUNEL assay a reduction on TUNEL-positive cells was observed in all the layers for both concentrations which allow to affirm that ketamine contributes to reducing cell death in the retina. Transmission electron microscopy (TEM) reaffirms this finding. Ketamine intravitreal pretreatment showed reduced ultrastructural changes. Our findings demonstrate that ketamine is safe for intravitreal use in doses up to 0.118 mmol.L-1. They seem to be particularly efficient to protect the retina from ischemic injury.

The effect of age on full-field electroretinograms recorded with skin electrodes

OBJECTIVES

The aim of this study was to determine whether age correlates with amplitude and latency, when full-field electroretinography (ERG) is performed using skin electrodes. The ability of pulse reference power line noise reduction (PURE) to dampen the noise associated with the use of skin electrodes, was also investigated.

METHODS

ERG was performed on 77 eyes in 77 healthy subjects (mean age: 55.6±19.0 years; age range: 9 to 86 years). Subjects with -5D or higher myopia, Emery-Little grade III or higher cataracts, retinal disease, uveitis, glaucoma, ≤5 mm mydriasis, or a history of intraocular surgery other than cataract surgery, were excluded. The active, reference, and ground electrodes were placed on the lower eyelid, outer canthus, and earlobe, respectively. Responses were averaged 10 times for dark-adapted (DA) ERGs, and 32 to 64 times for light-adapted (LA) ERGs. Noise was removed using the PURE method.

RESULTS

The DA ERGs without PURE were so noisy that the amplitude or latency could not be determined, whereas those with PURE were comparatively quieter. ERG with PURE demonstrated a significant negative correlation between age and amplitude and a significant positive correlation between age and latency.

CONCLUSIONS

We could record the measurable ERG waveforms with skin electrodes by using the PURE method, especially in fewer averaged conditions. It is suggested that skin electrode with PURE is suitable to examine the pathological ERGs, and other types of electrodes. It is recommended that the aging effect should be taken into consideration when pathological ERGs are evaluated.

Seizure triggered by flicker electroretinogram in a patient with no history of epilepsy

Purpose

It is well known that repetitive flash stimulation may trigger seizures in susceptible individuals. Nevertheless, reports of such incidents occurring during recording of a flash electroretinogram (ERG) are extremely rare. Here, we describe the case of a photic-induced seizure triggered during an ERG recording in the absence of a history of epilepsy or other paroxysmal events.

Methods

A 14-year-old male patient presented with reduced visual acuity and impaired mesopic vision. Ophthalmological exams confirmed the patient’s complaints but were inconclusive as to the underlying pathophysiology. An ERG recording was performed, during which the 30-Hz flicker stimulus triggered a seizure.

Results

The ERG was essentially normal, with the exception of a 7-Hz rhythm superimposed onto the flicker ERG response that was recorded when the seizure developed.

Conclusions

The present case highlights the possibility that the 30-Hz ERG flash stimulus triggers a seizure in patients with no previous paroxysmal events. Literature evidence suggests that the likelihood of such an incident could be reduced by stimulating monocularly.

THE USE OF ELECTRORETINOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY IN PATIENTS WITH SCHIZOPHRENIA

The use of electroretinography (ERG) and optical coherence tomography (OCT) has currently expanded beyond ophthalmology alone. The aim of this review is to present the results and knowledge acquired by these two methods in patients suffering from schizophrenia. Reviewing the studies applying ERG and OCT methods in the field of psychiatry, one can conclude that results of the research imply morphological and functional changes of retina in patients with schizophrenia that are not consistent. However, in most studies there was reduction of the amplitude and changes in the implicit time related parameters on ERG and thinning of the retinal nerve fiber layer on OCT. Neurons in the eye use the same neurotransmitters as neurons in the basal brain structures that are most affected in schizophrenia, according to the dopamine hypothesis of schizophrenia. Unlike neurons in the basal brain structures, the neurons in the eye are in vivo available to ERG. Using the aforementioned tests together with clinical diagnostic criteria of schizophrenia, the subgroups with different prognostic and therapeutic specificities within schizophrenia as a group of diseases might be identified more precisely.

Diagnosis of an X-linked type 2 congenital stationary night blindness using electroretinography and CACNA1F sequencing

A 4-year-old boy, with no history of relevance, presented with bilateral visual impairment, more so in scotopic conditions, and did not improve with optical correction. No significant funduscopic abnormalities were seen, leading to a suspicion of retinal dystrophy. Sequencing of the CACNA1F gene detected the c.3081C>A (p.Tyr1027Ter) mutation, which had occurred de novo in the patient's mother. This mutation, in the aforementioned clinical context, and with a compatible electronegative pattern, establishes the diagnosis of X-linked type 2 congenital stationary night blindness. Electrophysiology and genetic testing should be part of the diagnostic protocol for any unexplained loss of vision in children. The description, nomenclature and classification of hereditary retinal dystrophies based on their genotypic and electroretinograpic characteristics, avoids diagnostic errors due to their usual clinical and phenotypic overlap.

Daidzein ameliorates diabetic retinopathy in experimental animals

AIM

The present study was designed to check the effect of daidzein in the management of diabetic retinopathy.

MAIN METHODS

Streptozotocin at dose 55 mg/kg was used for inducing diabetes in rats. After 28 days of diabetic induction, animals were treated with daidzein at dose 25, 50, and 100 mg/kg for the next 28 days. Electroretinography, estimation of plasma glucose, lactate dehydrogenase, aldose reductase, sorbitol dehydrogenase and oxidative stress parameters were performed at the end of the study. Histopathology of retina was carried out at the end of the study.

KEY FINDINGS

Diabetic control animals showed a significant increase in levels of plasma glucose and plasma lactate dehydrogenase (p < 0.001). Treatment with daidzein at a dose of 50 and 100 mg/kg significantly reduced the elevated level of blood glucose (p < 0.01 and p < 0.01). Whereas, treatment with daidzein at a dose 100 mg/kg significantly reduced the elevated level of lactate dehydrogenase in plasma after 28 days of treatment (p < 0.01). Treatment with daidzein at a dose of 100 mg/kg significantly reduced the level of aldose reductase and sorbitol dehydrogenase (p < 0.01 and p < 0.001 respectively). Electroretinography revealed that daidzein treatment at a dose of 100 mg/kg significantly prevented the change in 'a' and 'b' wave amplitude and latency. Oxidative stress was also found to be significantly reduced after 28 days of daidzein treatment. Histopathological findings showed a reduction in retinal thickness after daidzein treatment.

SIGNIFICANCE

Daidzein treatment protected retina from damage in hyperglycaemic conditions. Thus, Daidzein can be considered as an effective treatment option for diabetic retinopathy.

Using retinal function to define ischemic exclusion criteria for animal models of glaucoma

Most animal models of glaucoma rely on induction of ocular hypertension (OHT), yet such models can suffer from high IOPs leading to undesirable retinal ischemia. Thus, animals with IOPs exceeding a threshold (e.g. > 60 mmHg) are often excluded from studies. However, due to the intermittent nature of IOP measurements, this approach may fail to detect ischemia. Conversely, it may also inappropriately eliminate animals with IOP spikes that do not induce ischemic damage. It is known that acute ischemia selectively impairs inner retinal function, which results in a reduced b-wave amplitude. Here, we explore the potential of using electroretinography (ERG) to detect ischemic damage in OHT eyes. 74 Brown Norway rats received a unilateral injection of magnetic microbeads to induce OHT, while contralateral eyes served as controls. IOP was measured every 2-3 days for 14 days after microbead injection. Retinal function was evaluated using dark-adapted bright flash ERG (2.1 log cd•s/m²) prior to, and at 7 and 14 days after, injection. We investigated two criteria for excluding animals: (IOP Criterion) a single IOP measurement > 60 mmHg; or (ERG Criterion) a b-wave amplitude below the 99.5% confidence interval for naïve eyes. 49 of 74 rats passed both criteria, 7 of 74 failed both, and 18 passed one criterion but not the other. We suggest that ERG testing can detect unwelcome ischemic damage in animal models of OHT. Since brief IOP spikes do not necessarily lead to ischemic retinal damage, and because extended periods of elevated IOP can be missed, such ERG-based criteria may provide more objective and robust exclusion criteria in future glaucoma studies.

Retinal ganglion cell ablation in guinea pigs

Guinea pigs are a common model of human ocular conditions; however, their visual function has not been fully characterized. The purpose of this study was to determine the contributions of retinal ganglion cells to structural and functional measures in guinea pigs. Healthy adult guinea pigs (n = 12) underwent unilateral optic nerve crush. Retinal structure was assessed with spectral domain optical coherence tomography (OCT), and thickness of the ganglion cell/nerve fiber layer (GC/NFL) was determined. Visual function was assessed with optomotor tracking of a drifting grating and light adapted electroretinograms (ERGs). From flash ERGs, a-wave, b-wave, oscillatory potentials (OPs), and photopic negative response (PhNR) were analyzed. From pattern ERGs, N1P1 and P1N2 were analyzed. Histological studies were done at various time points for ganglion cell quantification. Optomotor tracking was absent in optic nerve crush eyes following optic nerve crush. Significant thinning of the GC/NFL was evident four weeks following the crush. Flash ERGs revealed a significant reduction in the OP1 amplitude two weeks following crush (P < 0.01) and in the PhNR amplitude six weeks following crush (P < 0.01). There were no significant changes in a-wave, b-wave, or pattern ERG responses (P > 0.05 for all). In vivo OCT imaging showed progressive thinning of inner retinal layers. Ganglion cell density, quantified histologically, was significantly reduced by 75% in the optic nerve crush eye compared to the control eye at four weeks following crush. These findings indicate that retinal ganglion cells contribute to the PhNR and OP1 components of the full field flash ERG, but not significantly to the pattern ERG in guinea pigs. This study demonstrates that OCT imaging and full field flash ERGs are valuable in assessing retinal ganglion cell loss in vivo in guinea pigs and will help to further establish the guinea pig as a model of human ocular pathologies.

Electroretinography may reveal cognitive impairment among a cohort of subjects at risk of a major psychiatric disorder

INTRODUCTION

Almost a third of the offspring of parents diagnosed with schizophrenia or bipolar disorder could develop a mental disorder or related symptoms. The objectives of this study were to test the existence of two distinct subgroups of youth at-risk, according to their retinal response to luminance measured with electroretinography (ERG), and to relate the resulting cluster memberships with the cognitive clusters previously reported.

METHODOLOGY

A clustering analysis was performed with ERG measurements in 107 at-risk offspring. Each subgroup was compared to a healthy control group of 203 individuals. The ERG subgroup memberships were then associated with the cognitive clusters.

RESULTS

A two-cluster solution was obtained: HR-Cluster1 (n=53) showed a control-like ERG profile and HR-Cluster2 (n=54) showed reduced rod amplitudes and prolonged cone latencies of the b-wave. Subjects in the HR-Cluster2 were 2.7 times more likely to belong to the most detrimental cognitive subgroup than subjects in the HR-Cluster1 (49% Vs 18%).

CONCLUSION

At-risk offspring showed two distinct ERG profiles: a control-like and an altered profile. A higher risk of impaired cognitive function was observed in subjects with the altered ERG profile, suggesting the ERG as a potential biomarker of susceptibility to mental illness among youth at risk.

Effect of age and sex on neurodevelopment and neurodegeneration in the healthy eye: Longitudinal functional and structural study in the Long-Evans rat

The processes involved in neurodevelopment and aging have not yet been fully discovered. This is especially challenging in premorbid or borderline situations of neurodegenerative diseases such as Alzheimer's or glaucoma. The retina, as part of the central nervous system, can be considered the easiest and most accessible neural structure that can be analyzed using non-invasive methods. Animal studies of neuroretinal tissue in situations of health and under controlled conditions allow the earliest sex- and aging-induced changes to be analyzed so as to differentiate them from the first signs occurring in manifested disease. This study evaluates differences by age and sex based on intraocular pressure (IOP) and neuroretinal function and structure in healthy young and adult rats before decline due to senescence. For this purpose, eighty-five healthy Long-Evans rats (31 males and 54 females) were analyzed in this 6-month longitudinal study running from childhood to adulthood. IOP was measured by tonometer (Tonolab; Tiolat Oy Helsinki, Finland), neuroretinal function was recorded by flash scotopic and light-adapted photopic negative response electroretinography (ERG) (Roland consult® RETIanimal ERG, Germany) at 4, 16 and 28 weeks of age; and structure was evaluated by in vivo optical coherence tomography (OCT) (Spectralis, Heidelberg® Engineering, Germany). Analyzing both sexes together, IOP was below 20 mmHg throughout the study; retina (R), retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) thicknesses measured by OCT decreased over time; an increase in ERG signal was recorded at week 16; and no differences were found between right and left eyes. However, analyzing differences by sex revealed that males had higher IOP (even reaching ocular hypertension [>20 mmHg] by the end of the study [7 months of age]), exhibited greater neuroretinal thickness but higher structural percentage loss, and had worse dark- and light-adapted function as measured by ERG than females. This study concludes that age and sex influenced neurodevelopment and neurodegeneration. Different structural and functional degenerative patterns were observed by sex; these occurred earlier and more intensely in males than in age-matched females.

[Preliminary clinical observations of retina injury in alkaline ocular trauma patients]

Objective: To investigate the features of the full-field electroretinogram (FERG) in patients with ocular surface alkaline injury, and to clarify the clinical significance of FERG examination in alkaline ocular trauma. Methods: Retrospective series of case study. A total of 22 patients with chemical ocular surface injury who were treated in the Department of Ophthalmology of Peking University Third Hospital from May 2018 to January 2020 were selected, including 20 males (25 eyes) and 2 females (2 eyes). The age ranged from 19 to 60 years old (average, 41). There were 17 eyes with alkaline ocular trauma, 7 eyes with thermal burn, and 3 eyes with acid ocular trauma. Seventeen contralateral healthy eyes in patients with unilateral mechanical trauma were used as controls. Fourteen alkaline trauma eyes with visual acuity records were further observed according to the degree of visual impairment. All patients were subjected to different flash intensity stimuli in accordance with a standard of the International Society for Clinical Electrophysiology of Vision for dark-adapted and light-adapted full-field FERG. One-way ANOVA and SNK-q was used for the comparison between groups. The unpaired t test was used for the comparison of patients with different vision. Results: Compared with healthy eyes the injured eyes' amplitude of dark adaption FERG b-wave under the dark stimulation of 0.01 cd·s·m^-2 in alkaline ocular trauma, thermal burn, acid ocular trauma was (135±85), (169±55), and (112±43) versus (341±53) μV, respectively; compared with healthy eyes, the differences were statistically significant (F=31.38; q=8.94, 5.70， 5.45；all P<0.01). Compared with healthy eyes the injured eyes' amplitude of dark adaption FERG a-wave under the dark stimulation of 3.00 cd·s·m^-2 in alkaline ocular trauma, thermal burn, acid ocular trauma was (178±78), (172±35), and (99±53) versus (334±60) μV, respectively; compared with healthy eyes, the differences were statistically significant (F=24.33; q=7.04， 5.60， 5.80；all P<0.01). Compared with healthy eyes the injured eyes' amplitude of dark adaption FERG b-wave under the dark stimulation of 3.00 cd·s·m^-2 in alkaline ocular trauma, thermal burn, acid ocular trauma was (354±79), (342±77), and (352±201) versus (600±78) μV, respectively; compared with healthy eyes, the differences were statistically significant (F=27.68; q=8.11， 6.51， 4.48； all P<0.01). Compared with healthy eyes the injured eyes' amplitude of dark adaption FERG OPs under the dark stimulation of 3.00 cd·s·m^-2 in alkaline ocular trauma, thermal burn, acid ocular trauma was (97±54), (107±41), and (45±22) versus (206±32) μV, respectively; compared with healthy eyes, the differences were statistically significant (F=25.03; q=7.36， 5.13， 5.96； all P<0.01).There was no significant difference in FERG between patients with visual acuity≥0.2 and those with visual acuity<0.2 (P>0.05) after alkaline ocular trauma. Conclusions: By detecting the amplitude change of FERG wave form of chemical ocular trauma, in this study, the amplitude of FERG wave form in alkaline ocular trauma was generally decreased. It's suggested that alkaline ocular trauma can cause damage to the rod and cone systems of retinal. (Chin J Ophthalmol, 2020, 56: 514-518).

Rod bipolar cell dysfunction in POLG retinopathy

OBJECTIVE

To report the clinical and novel electrophysiological features in a child with POLG-related sensory ataxic neuropathy, dysarthria and ophthalmoparesis (SANDO).

METHODS

The proband, a male child of Indian descent, underwent serial systemic and ophthalmological evaluations from birth until 14 years of age. Eye examinations included visual acuity and extraocular movement assessments, fundus photography, spectral domain optical coherence tomography and full-field electroretinography (ERG). Detailed genetic testing was also performed.

RESULTS

The child carried a homozygous mutation in POLG (c.911T > G/p.Leu304Arg) and manifested systemic features such as seizures, headaches, areflexia, hypotonia, myopathy and vomiting. The child's distance visual acuity was 0.50 and 0.40 LogMAR in the right and left eyes, respectively. Bilateral ophthalmoplegia and ptosis were observed at 5 years of age. The dark-adapted (DA) ERG responses to 2.29 cd s m^-2 and 7.6 cd s m^-2 stimuli showed a markedly reduced b/a ratio; an electronegative configuration was noted to a DA 7.6 ERG.

CONCLUSION

This is the first documented case of an electronegative ERG in a POLG-related disorder consistent with generalized rod ON-bipolar dysfunction. The rest of the proband's systemic and ophthalmological features were consistent with SANDO but some features overlapped with other POLG-related disorders such as Alpers-Huttenlocher syndrome and autosomal dominant progressive external ophthalmoplegia demonstrating the wide phenotypic overlap expected due to POLG mutations.

Developments in non-invasive visual electrophysiology

To study the physiology of the primate visual system, non-invasive electrophysiological techniques are of major importance. Two main techniques are available: the electroretinogram (ERG), a mass potential originating in the retina, and the visual evoked potential (VEP), which reflects activity in the primary visual cortex. In this overview, the history and the state of the art of these techniques are briefly presented as an introduction to the special issue "New Developments in non-invasive visual electrophysiology". The overview and the special issue can be used as the starting point for exciting new developments in the electrophysiology of primate and mammalian vision.

Normal to supernormal 30-Hz flicker ERGs predict visual function and prognosis in central retinal artery occlusion

PURPOSE

To determine whether normal to supernormal 30-Hz flicker ERGs are associated with visual function and prognosis in patients with central retinal artery occlusion (CRAO).

METHODS

A total of 133 patients diagnosed with unilateral acute non-arteritic CRAO by examination with electroretinography (ERG) were examined. Thirty-hertz flicker ERG amplitudes were analyzed according to the severity of CRAO, and their correlation with visual function and prognosis was assessed. All patients were categorized into one of three groups according to the flicker ERG amplitude ratios between affected and fellow eyes: ≥ 110%, supernormal; 90-110%, normal; and < 90%, subnormal.

RESULTS

Thirty-hertz flicker ERG parameters differed significantly according to the severity of retinal ischemia, i.e., between incomplete versus complete CRAO: mean amplitude (55.89 ± 24.38 > 45.41 ± 23.47 μV, P = 0.029), amplitude ratio (76.1 ± 23.1% > 58.7 ± 25.7%, P < 0.001), and proportion of normal to supernormal flicker ERGs (30.5% > 12.4%, P < .001). One-month and final follow-up visual function and prognosis were better in the normal to supernormal flicker ERGs: 1 month BCVA (1.55 ± 0.65 > 2.05 ± 0.61 logMAR, P < .001), final BCVA (1.32 ± 0.79 > 1.97 ± 0.68 logMAR, P < .001), 1-month VA improvement (- 0.50 ± 0.47 > - 0.10 ± 0.29 logMAR, P < .001), and final VA improvement (- 0.74 ± 0.61 > - 0.18 ± 0.37 logMAR, P < .001).

CONCLUSIONS

Normal to supernormal 30-Hz flicker ERG changes in eyes with CRAO are associated with the milder severity of retinal ischemia and showed better visual function and outcome than the subnormal ERG group.

Evaluation of primary internal limiting membrane peeling in cases with rhegmatogenous retinal detachment

Background

Epiretinal membranes (ERMs) have been reported after pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment (RRD). Peeling of the internal limiting membrane (ILM) can prevent post-PPV ERM formation but has a potential negative impact on macular structure and function.

Purpose

To investigate the anatomical and functional outcomes of ILM peeling during PPV for primary RRD.

Methods

This was a prospective nonrandomized study that included 60 eyes of 60 patients with a primary macula-off RRD and less than grade C proliferative vitreoretinopathy (PVR). Eyes were allocated into 2 groups; Group A underwent PPV without ILM peeling and Group B had ILM peeling. At postoperative month 6, all patients underwent retinal imaging using spectral domain optical coherence tomography (OCT) and OCT angiography and macular function was assessed using multifocal electroretinogram (mfERG). Baseline characteristics and postoperative anatomical and visual outcomes were recorded and statistically analyzed.

Results

We enrolled 30 eyes of 30 patients in each group. In Group A, mean age was 44.6 years, while the mean age of Group B patients was 49.9 years. Postoperative LogMAR visual acuity was significantly better in Group A than in Group B (p < 0.001). ERMs were demonstrated on OCT in 13.3% of Group A and none of Group B patients (p = 0.04). Retinal dimples were found in 53.3% of Group B and none of Group A eyes (p < 0.001). OCTA showed a greater vessel density of the superficial capillary plexus (SCP) in Group A compared to Group B eyes (p = 0.046), while no difference was found regarding deep capillary vessel density (p = 0.7). Mean amplitude of mfERG P1 wave was significantly higher in Group A eyes than in Group B (p = 0.002). Both the SCP vessel density and P1 amplitude were positively correlated with visual acuity (p < 0.001).

Conclusion

This study suggests that ILM peeling prevents ERM development in eyes undergoing PPV for uncomplicated macula-off RRD, but potential damage to macular structure and function were found.

Trial registration Retrospectively registered on 09/24/2019 on ClinicalTrials.gov with an ID of NCT04139811.

Retinal functioning and reward processing in schizophrenia

Retinal responses to light, as measured by electroretinography (ERG), have been shown to be reduced in schizophrenia. Data from a prior ERG study in healthy humans indicated that activity of a retinal cell type affected in schizophrenia can be modified by the presence of a food reward. Therefore, we aimed to determine whether ERG amplitudes would be sensitive to the well-documented reward processing impairment in schizophrenia. Flash ERG data from 15 clinically stable people with schizophrenia or schizoaffective disorder and 15 healthy controls were collected under three conditions: baseline, anticipation of a food reward, and immediately after consuming the food reward. At the group level, data indicated that controls' ERG responses varied as a function of salience of the food reward (baseline vs. anticipation vs. consumption) whereas patients' ERG responses did not vary significantly across conditions. Correlations between ERG amplitudes and scores on measures of hedonic capacity (including motivation and pleasure negative symptom ratings for patients) indicated consistent relationships. These data suggest that flash ERG amplitudes may be a sensitive indicator of the integrity of reward processing mechanisms. However, several differences in the direction of findings between this and a prior study in controls point to the need for further investigation of the contributions of a number of key variables to the observed effects.

Retinal function anomalies in young offspring at genetic risk of schizophrenia and mood disorder: The meaning for the illness pathophysiology

BACKGROUND

Visual defects are documented in psychiatric disorders such as schizophrenia, bipolar disorder and major depressive disorder. One of the most consistent alterations in patients is a change in cone and rod electroretinographic (ERG) responses. We previously showed a reduced rod b-wave amplitude in a small sample of young offspring born to an affected parent. A confirmation of the patients ERG anomalies in young offspring at high genetic risk would offer a new approach to the neurodevelopmental investigation of the illness. We thus investigated cone and rod responses in a larger sample of young healthy high-risk offspring.

METHODS

The ERG was recorded in 99 offspring of patients having DMS-IV schizophrenia, bipolar or major depressive disorder (mean age 16.03; SD 6.14) and in 223 healthy controls balanced for sex and age. The a- and b-wave latency and amplitude of cones and rods were recorded.

RESULTS

Cone b-wave latency was increased in offspring (ES = 0.31; P = 0.006) whereas rod b-wave amplitude was decreased (ES = -0.37; P = 0.001) and rod latency was increased (ES = 0.35; P = 0.002).

CONCLUSIONS

The ERG rod and cone abnormal response previously reported in adult patients having schizophrenia, bipolar disorder or major depressive disorder are detectable in genetically high-risk offspring as early as in childhood and adolescence. Moreover, a gradient of effect sizes among offspring and the three adult diagnoses was found in the cone response. This suggests that ERG waveform as a risk endophenotype might become part of the definition of a "childhood risk syndrome".

People with current major depression resemble healthy controls on flash Electroretinogram indices associated with impairment in people with stabilized schizophrenia

Flash electroretinography (fERG) has been used to identify anomalies in retinal functioning in several psychiatric disorders. In schizophrenia (SCZ), fERG abnormalities are reliably observed, but findings from studies of major depressive disorder (MDD) have been less consistent. In this study, fERG data were recorded from MDD patients in a current major depressive episode (n = 25), and compared to data from SCZ patients (n = 25) and healthy controls (HC; n = 25), to determine the degree to which fERG anomalies in acute MDD overlap or contrast with those observed in stabilized (though not symptom free) SCZ. The primary variables of interest were a-wave (photoreceptor activity), b-wave (bipolar-Müller cell activity), and photopic negative response (PhNR; ganglion cell activity) amplitudes and implicit times. Across most conditions, there were no significant differences between the MDD and HC groups in a- or b-wave response, but the SCZ group consistently demonstrated reduced amplitudes. Interestingly, MDD patients demonstrated an increase in photopic a-wave implicit time relative to SCZ patients, and a decrease in PhNR implicit time relative to controls. Correlations between BDI-II scores and fERG metrics were not significant for either patient group. Overall, these data indicate that, using an fERG protocol that distinguishes SCZ patients from controls, MDD patients experiencing a current depressive episode closely resemble healthy controls in their fERG responses. Therefore, MDD-related fERG changes may be more subtle than those observed in SCZ and detectable only with larger sample sizes than we employed and/or using a different set of fERG test parameters.

Improvement of reduced electroretinographic responses in thymoma-associated retinopathy: a case report and literature review

PURPOSE

To report a patient with thymoma-associated retinopathy presenting as having a good visual prognosis.

METHODS

Case report and literature review.

CASE REPORT

A 42-year-old female patient was referred to our hospital for complaints of sudden visual-field defects bilaterally. Decimal corrected visual acuity (VA) was 1.5 and 1.2 in the right (RE) and left eyes (LE), respectively. Fundus autofluorescence revealed hyper-autofluorescence from the posterior pole to mid-peripheral retina in both eyes. Full-field electroretinography (ERG) amplitudes were reduced to 20-50% and 30-50% of our controls for the scotopic and photopic conditions, respectively. A systemic examination revealed the presence of thymoma, and the patient underwent thymectomy and immunosuppression therapies. Immunohistochemical analysis using the patient's serum showed immunolabeling on the photoreceptor inner segment and outer plexiform layer in the monkey retina. Two years later, VA remained at 1.5 and 1.2 in RE and LE. ERG amplitudes improved to 30-60% of the controls for the scotopic conditions. However, photopic ERG showed no remarkable change.

CONCLUSIONS

To our knowledge, improvement of reduced rod-mediated ERG responses has not been described in seven previously reported patients with thymoma-associated retinopathy. The good visual prognosis of our patient may be associated with well-timed intervention.

[Clinical observation of electroretinogram examination in ocular alkali burn]

Objective: To investigate the wave variations of the electroretinography (ERG), and explore the clinical value of using ERG in alkali injury. Methods: A total of 13 patients with alkali burns who were treated in the Department of Ophthalmology of Peking University Third Hospital from May 2018 to October 2019 were selected, including 12 males and 1 female. The age ranged from 19 to 60 years old. A total of 15 injured eyes were used as the alkali burn group, meanwhile, another 15 contralateral eyes with mechanical unilateral trauma were used as the healthy controls. ERG examination was performed to compare the amplitudes of 6 activation-induced responses between the two groups. Results: Compared with control group, b-wave amplitude of dark adaption 0.01 ERG in alkali injury group decreased [(137±23) μV vs (348±14) μV, P<0.001]. Compared with control group [(335±17) μV and (368±19) μV], a-wave amplitude of dark adaption 3.0 ERG and 10.0 ERG in alkali injury groups [(172±20) μV and (220±21) μV] were decreased (both P<0.001). As for b-wave amplitude of dark adaption 3.0 ERG and 10.0 ERG, compared with control group [(610±20) μV and (612±19) μV], those of alkali injury groups [(359±21) μV and (384±21) μV] were decreased (both P<0.001). In terms of oscillatory potentials (OPs) amplitude of dark 3.0 ERG adaption, compared with control group [(209±8) μV], that of alkali injury group [(94±13) μV] was decreased (P<0.001). Compared with normal group [(58±3) μV], a-wave amplitude of light adaption 3.0 ERG in alkali injury group [(40±4) μV] was decreased (P<0.001). As for b-wave amplitude of light adaption 3.0 ERG, compared with control group [(146±6) μV], that of alkali injury group [(90±11) μV] was decreased (P<0.001). In terms of photopic 3.0 flicker 30 Hz of light adaption, compared with control group [(166±10) μV], that of alkali injury group [(93±11) μV] was decreased (P<0.001). Conclusion: Alkali injury can cause ocular surface morphological changes, meanwhile, it leads to the alternations of the visual function.

Multimodal imaging in a family with Cockayne syndrome with a novel pathogenic mutation in the ERCC8 gene, and significant phenotypic variability

BACKGROUND

Cockayne syndrome is a rare autosomal recessive neurodegenerative disorder caused by mutations of either the ERCC6/CSB or ERCC8/CSA genes. Here, we describe two sisters with Cockayne syndrome caused by compound heterozygous mutations in the ERCC8 gene using multimodal imaging. Significant ophthalmic and systemic phenotypic variability is discussed.

MATERIALS AND METHODS

Multimodal imaging was performed in two affected sisters and included electroretinography, optical coherence tomography, ultra-wide-field confocal scanning laser ophthalmoscopy, fundus autofluorescence and fluorescein angiography, and magnetic resonance imaging. Genetic analyses were performed on the affected sisters, both parents, and three unaffected siblings.

RESULTS

The older sister (Patient 1) had mental retardation, bilateral hearing loss, ataxia, and decreased visual acuity with retinal dystrophy. Radiographic studies revealed microcephaly, cerebral and cerebellar atrophy, ventriculomegaly, and a diffusely thickened skull. Full-field electroretinography waveforms were severely diminished with attenuation of cone and rod responses. The younger sister (Patient 2) had similar clinical features, including ataxia, bilateral hearing loss, and decreased visual acuity with retinal dystrophy. She also had paranoid schizophrenia. Wide-field fundus autofluorescence showed scattered areas of retinal pigment epithelium atrophy, which was different from her sister. Genetic analysis revealed two mutations in the ERCC8 gene shared by the sisters. These include an unreported missense point mutation: p.Thr328Ser:c.983C > G, and another previously reported pathogenic missense mutation: p.Ala205Pro:c.613G > C. Familial testing showed in trans segregation of these mutations with unaffected siblings inheriting one or neither mutation, but not both.

CONCLUSION

The clinical presentation and genetic studies confirmed a diagnosis of Cockayne syndrome in both sisters caused by compound heterozygous mutations in the ERCC8 gene on chromosome 10. Multimodal ocular imaging and systemic findings revealed wide phenotypic variability between the affected siblings.

ERG Alteration Due to the rd8 Mutation of the Crb1 Gene in Cln3 +/+ rd8-/rd8- Mice

Mattapallil et al. described that vendor lines for C57BL/6 N mice may carry the rd8 mutation that leads to an ocular phenotype, which could be mistaken for an induced retinal degeneration. This mouse strain is widely used in ophthalmic research as a background for modeling retinal degeneration. In the process of studying Cln3^Δex7/8 knock-in mice on a C57BL/6 N background, we became aware of this issue. The aim of this study thus was to use electroretinography to investigate the age-dependent functional loss in Cln3^{+/+ rd8-/rd8-} mice and compare it to C57BL/6 J mice.The scotopic and photopic amplitudes of the a-wave and b-wave decrease significantly in mutant mice with increasing age, and the implicit time is prolonged. Especially the oscillatory potentials arising from inner retinal interaction seem to be notably affected by the rd8 mutation. Surprisingly, the amplitudes in young C57BL/6 J mice were lower than those measured in C57BL/6 N at any time point.Our results indicate that the rd8 mutation present in C57BL/6 N mice affects the function of the inner and outer retina. This is surprising given that the major retinal morphological alterations due to the rd8 mutation are found in the outer retina.We conclude that the rd8 mutation does affect the retinal function in Cln3^{+/+ rd8-/rd8-} mice in a variable manner. Epigenetic factors and modifying genes lead to a phenotype shift in these mice. Interpreting the results of previous studies in mutant mice on C57BL/6 N background is challenging as comparing results obtained in independent studies or on other mouse backgrounds may be misleading. Using littermates as controls remains the only valid option.

Light deprivation reduces the severity of experimental diabetic retinopathy

Illumination of the retina is a major determinant of energy expenditure by its neurons. However, it remains unclear whether light exposure significantly contributes to the pathophysiology of common retinal disease. Driven by the premise that light exposure reduces the metabolic demand of the retina, recent clinical trials failed to demonstrate a benefit for constant illumination in the treatment of diabetic retinopathy. Here, we instead ask whether light deprivation or blockade of visual transduction could modulate the severity of this common cause of blindness. We randomized adult mice with two different models of diabetic retinopathy to 1-3 months of complete dark housing. Unexpectedly, we find that diabetic mice exposed to short or prolonged light deprivation have reduced diabetes-induced retinal pathology, using measures of visual function, compared to control animals in standard lighting conditions. To corroborate these results, we performed assays of retinal vascular health in diabetic Gnat1^-/- and Rpe65^-/- mice, which lack phototransduction. Both mutants displayed less diabetes-associated retinal vascular disease compared to respective wild-type controls. Collectively, these results suggest that light-induced visual transduction promotes the development of diabetic retinopathy and implicate photoreceptors as an early source of visual pathology in diabetes.

Reproducibility of Full-field Electroretinogram Measurements in Birdshot Chorioretinopathy Patients: An Intra- and Inter-visit Analysis

Purpose: Aims to determine the variability of ffERG measurements in patients with clinically stable birdshot chorioretinopathy (BCR).Methods: Repeatability coefficients (RC) of ffERG amplitudes and implicit times were calculated from 11 BCR patients. Jackknife resampling estimated 95% confidence intervals of each ERG parameter's RC and the percentage change explained by variability alone was calculated.Results: Intra-visit variability in ffERG parameters was lower than inter-visit. Intravisit RCs demonstrated that for intravisit ERG testing, there was less than 30% variation in ERG amplitude for most parameters. For inter-visit ERG testing, a greater than 40% reduction in ERG amplitude may be clinically meaningful for 6 of 8 ERG parameters. Photopic single flash responses have <2 msec of test-retest variability both within and across visits.Conclusions: A 40% reduction in ERG amplitude and/or a delay of >2 msec in the photopic single flash response may be suitable criteria for meaningful change in BCR patients.

Multifocal electroretinography in amblyopia

PURPOSE

To identify whether there are functional abnormalities in the retina of amblyopic eyes using multifocal electroretinography (mfERG).

METHODS

This is a prospective study of patients ≥ 7 years of age identified with unilateral amblyopia (strabismic or anisometropic). Multifocal ERG and flash ERG were performed to compare parameters between the amblyopic and non-amblyopic fellow eyes. A complete analysis of the five ring averages was done including the central ring.

RESULTS

Thirty-eight patients were included: mean age was 14.3 ± 7.3 years; 18 patients were strabismic and 20 were anisometropic. Amblyopic eye responses across the rings in multifocal ERG were diminished compared with fellow non-amblyopic eyes with significant differences detected in the central rings (p = 0.001). On the other hand, flash ERG did not show any consistently significant differences. When divided by severity, amplitudes of central rings were significantly lower in severely amblyopic eyes compared with non-amblyopic eyes (p = 0.001), while in mild amblyopia, no significant differences were observed. No significant difference was observed between anisometropic and strabismic amblyopic eyes.

CONCLUSIONS

Using multifocal ERG, significantly decreased amplitudes were observed in amblyopic eyes compared with normal fellow eyes in the central ring. This correlated with the severity of amblyopia. No difference was observed when comparing the two groups of amblyopia (strabismic and anisometropic). Those findings may help clarify the pathophysiology of amblyopia better and open the door for new objective ways to monitor the response to amblyopia treatment but this needs to be further studied.

Early onset retinal dystrophies: clinical clues to diagnosis for pediatricians

Introduction

Inherited retinal dystrophies are major cause of severe progressive vision loss in children. Early recognition and diagnosis are essential for timely visual rehabilitation during the appropriate stages of the visual development, as well as for genetic diagnosis and possible gene therapy. The aim of this study is to characterize a pattern of the initial visual symptoms, which could help the pediatricians and the primary care providers to suspect an inherited retinal disorder in its early stage.

Methods

We analyzed the initial clinical symptoms, based on parental report during the first visit to specialist, in 50 children diagnosed with retinal dystrophy confirmed by full-field electroretinography. The analysis included the age of symptoms onset and the type of visual symptoms, both in the total population and in the following diagnostic subgroups: rod-cone dystrophy (n.17), cone-rod dystrophy (n.12), achromatopsia (n.13), congenital stationary night blindness (n.6) and Leber’s congenital amaurosis (n.2).

Results

The majority of children (80%) had the onset of clinical symptoms before one year of age. The most frequent visual complaints reported by parents were nystagmus (76%), visual loss (28%) and photophobia (8%). Nystagmus was the first symptom reported by parents if the disease onset was before the age of six months, while the onset after the six months of age was more likely associated with the complain of vision loss.

Conclusions

Low vision and nystagmus observed by parents, particularly in the first year of life, may represent a red flag, prompting an appropriate ophthalmological workup for inherited retinal dystrophy.

Unique retinal signaling defect in GNB5-related disease

OBJECTIVE

To report a unique retinal signaling defect in GNB5-related disease.

METHODS

A 3-year-old female child underwent detailed systemic and ophthalmological evaluation. The eye examination included fundus photography, spectral domain optical coherence tomography and an extended protocol full-field electroretinography (ERG) including the ISCEV recommended standard steps. The dark-adapted (DA) ERGs were performed to a series of white flashes (range 0.006-30.0 cd s m^-2) and two red flashes. The DA ERGs to higher stimulus intensities (3.0, 10.0 and 30.0 cd s m^-2) were tested using a range of inter-stimulus intervals (ISI) of up to 60 s. In addition to standard light-adapted (LA) ERGs, a short-duration (0.5 s) LA 3.0 30-Hz flicker ERG and a long-duration LA ON-OFF ERG were also performed. Genetic testing included microarray, mitochondrial genome testing and whole exome sequencing.

RESULTS

The child was diagnosed to have status epilepticus and bradycardia at 6 months of age. Subsequently, she was diagnosed to have global developmental delay and hypotonia. On ophthalmological evaluation, the child fixes and follows light. Fundus evaluation showed mild optic disk pallor; macular SD-OCT was normal. The dim flash DA ERGs (DA 0.006 and DA 0.01 cd s m^-2) were non-detectable. DA red flash ERGs showed the presence of an x-wave (cone component) and no rod component. The DA 3.0, 10.0 and 30.0 ERGs showed electronegative configuration regardless of the ISI; the averaged a-wave amplitude (4 flashes) was smaller at shorter ISI but became normal at a prolonged ISI (60 s). The LA 30-Hz flicker ERG was severely reduced but detectable for the initial 0.5 s; this became non-detectable after 5 s of averaging. The LA 3.0 2-Hz ERG showed markedly reduced a- and b-wave amplitudes and a reduced b:a ratio; the LA ON-OFF ERGs were non-detectable. WES identified a homozygous null mutation in G protein subunit beta 5 (GNB5; c.1032C>A/p.Tyr344*).

CONCLUSION

This report identifies for the first time a unique retinopathy associated with biallelic mutations in GNB5. The observed phenotype is consistent with a dual retinal signaling defect reminiscent of features of bradyopsia and rod ON-bipolar dysfunction.

Vision in the snapping shrimp Alpheus heterochaelis

Snapping shrimp engage in heterospecific behavioral associations in which their partners, such as goby fish, help them avoid predators. It has been argued that snapping shrimp engage in these partnerships because their vision is impaired by their orbital hood, an extension of their carapace that covers their eyes. To examine this idea, we assessed the visual abilities of snapping shrimp. We found the big claw snapping shrimp, Alpheus heterochaelis, has spatial vision provided by compound eyes with reflecting superposition optics. These eyes view the world through an orbital hood that is 80-90% as transparent as seawater across visible wavelengths (400-700 nm). Through electroretinography and microspectrophotometry, we found the eyes of A. heterochaelis have a temporal sampling rate of >40 Hz and have at least two spectral classes of photoreceptors (λ_max=500 and 519 nm). From the results of optomotor behavioral experiments, we estimate the eyes of A. heterochaelis provide spatial vision with an angular resolution of ∼8 deg. We conclude that snapping shrimp have competent visual systems, suggesting the function and evolution of their behavioral associations should be re-assessed and that these animals may communicate visually with conspecifics and heterospecific partners.

The impacts of individual and combined exposure to cadmium and lead on intraocular pressure, electroretinography, and residual changes in the rabbit eyes

The human eye is very vulnerable to various environmental pollutants. Cadmium (Cd) and lead (Pb) are widely spread heavy metals. The goal of the existing study is to explore the impact of single or joint exposure to Cd and Pb on the eye indicators. In this study, male New Zealand white rabbits were treated orally for 30 days with Cd (5 mg Cd Cl₂/kg bw) associated or not with Pb (12.5 mg lead acetate/kg bw). Fundus and slit lamp examinations, electroretinography (ERG), intraocular pressure (IOP), Cd and Pb residues, and the histopathological picture of the eye were studied. The results revealed that the oral dosing of Cd or Pb evoked a significant (p < 0.05) decline in a- and b-wave amplitudes, under scotopic conditions, and IOP values. Single Pb or Cd treatment showed a significant (p < 0.001) increase in their residues in the whole eye tissue of the Pb- or Cd-treated group. Eye structures of Cd- or Pb-intoxicated rabbit showed mild degenerated changes of cornea and sclera tissues with the presence of irregular variably sized eosinophilic droplets in the lens. Notably, the simultaneous exposure to Cd and Pb leads to an antagonistic outcome in all of the estimated parameters. These findings concluded that oral exposure to Cd or Pb could significantly disturb the vision but their joint exposure caused an opposing effect on nearly all of these disturbances.

Verifying complaints of difficulties in night vision using electroretinography and dark adaptation tests

PURPOSE

To determine the electroretinographical and psychophysical parameters that can help to verify patients' complaints of reduced night vision.

METHODS

We tested 275 consecutive patients with normal appearing fundi, complaining of visual difficulties at night, using flash electroretinography (ERG) and dark adaptation (DA) test. Two ERG parameters were used to assess a scotopic retinal function: the amplitude of the response to dim blue flash (the rod response) and the b-wave ratio (measured/expected). Dark adaptation was measured with green- and red-light stimuli after exposure to a bright, bleaching light. The psychophysical parameter of night vision was defined as the threshold for detection of the blue-green stimulus that was measured after 40-45 min in complete darkness.

RESULTS

Fifty-five patients were excluded from the analysis because of a discrepancy between the two ERG parameters in assessment of scotopic retinal function. The remaining 220 patients were divided into 4 groups: (1) normal ERG and normal DA, (2) subnormal ERG and subnormal DA, (3) normal ERG and subnormal DA and (4) subnormal ERG and normal DA. The ERG and DA tests supported the complaint of visual difficulties at night in 67 patients (group 2), while 34 patients were characterized as having normal scotopic visual function (group 1). The other 119 patients (groups 3 and 4) presented a diagnostic dilemma because one test (ERG or dark adaptation) showed normal scotopic function, while the other indicated subnormal scotopic function.

CONCLUSION

Our findings indicate that ERG is an essential, but not sufficient test for verifying patient's complaint on visual difficulties in the dark. We suggest using both electroretinography and psychophysical dark adaptation to test patients complaining of reduced night vision.

Electroretinography in psychiatry: A systematic literature review

This review aims to consolidate the available information on use of electroretinography as a diagnostic tool in psychiatry. The electroretinogram (ERG) has been found to have diagnostic utility in cocaine withdrawal (reduced light-adapted b-wave response), major depressive disorder (reduced contrast gain in pattern ERG), and schizophrenia (reduced a- and b-wave amplitudes). This review examines these findings as well as the applicability of ERG to substance use disorder, Alzheimer's disease, autism spectrum disorder, panic disorder, eating disorders, attention deficit hyperactivity disorder, and medication use. While there have been promising results, current research suffers from a lack of specificity. Further research that quantifies anomalies in ERG present in psychiatric illness is needed.

Electroretinograms before and after extraction of large intraocular iron foreign body

Purpose

We present our findings in a case with an intraocular foreign body in which the electroretinographic (ERG) findings were useful.

Observations

A 37-year-old man was injured by an iron fragment that penetrated into his left eye through the cornea. His visual acuity was counting fingers, and a traumatic cataract prevented an examination of the fundus. B-mode ultrasonography showed a stick-like foreign body of approximately 14 mm in length in the eye. Preoperative ERGs with a contact lens electrode showed reduced responses with many blinking artifacts. Lensectomy and pars plana vitrectomy were performed and a fragment of a wire brush was seen embedded in the superior nasal retina which was removed. The decimal visual acuity improved to 1.2 two weeks later. The postoperative ERG performed with a skin electrode showed reduced responses in the injured eye.

Conclusions and importance

We recommend that the physiology of the retina be assessed by recording ERGs with a skin-type electrode as soon as possible after a traumatic injury to the eye.

Intracameral injection of a chemically cross-linked hydrogel to study chronic neurodegeneration in glaucoma

Investigation of neurodegeneration in glaucoma, a leading cause of irreversible blindness worldwide, has been obfuscated by the lack of an efficient model that provides chronic, mild to moderate elevation of intraocular pressure (IOP) with preservation of optical media clarity for long term, in vivo interrogation of the structural and functional integrity of the retinal ganglion cells (RGCs). Here, we designed and formulated an injectable hydrogel based on in situ cross-linking of hyaluronic acid functionalized with vinyl sulfone (HA-VS) and thiol groups (HA-SH). Intracameral injection of HA-VS and HA-SH in C57BL/6J mice exhibited mild to moderate elevation of IOP with daily mean IOP ranged between 14 ± 3 and 24 ± 3 mmHg, which led to progressive, regional loss of RGCs evaluated with in vivo, time-lapse confocal scanning laser ophthalmoscopy; a reduction in fractional anisotropy in the optic nerve and the optic tract projected from the eye with increased IOP in diffusion tensor magnetic resonance imaging; a decrease in positive scotopic threshold response in electroretinography; and a decline in visual acuity measured with an optokinetic virtual reality system. The proportion of RGC loss was positively associated with the age of the animals, and the levels and the duration of IOP elevation. The new glaucoma model recapitulates key characteristics of human glaucoma which is pertinent to the development and pre-clinical testing of neuroprotective and neuroregenerative therapies. STATEMENT OF SIGNIFICANCE: A new model to study chronic neurodegeneration in glaucoma has been developed via intracameral injection of a specifically designed hyaluronic acid functionalized with vinyl sulfone and thiol groups for cross-linking. Intracameral injection of the chemically cross-linked hydrogel generates mild to moderate IOP elevation, resulting in progressive degeneration of the retinal ganglion cells, optic nerve, and optic tract, and a decline in visual function. The model recapitulates the key features of neurodegeneration in human glaucoma, which will facilitate and expedite the development of neuroprotective and neuroregenerative therapies.

Novel findings in enhanced S-cone syndrome: a case with macular retinal neovascularization and severe retinal vasculitis

PURPOSE

To describe a novel association of enhanced S-cone syndrome (ESCS) with macular retinal neovascularization and severe retinal vasculitis.

METHODS

Clinical examination, spectral domain optical coherence tomography, fluorescein angiography, fundus autofluorescence, infrared reflectance and electroretinography were used to study a 25-year-old male with a history of night blindness from early childhood and recent accelerated visual loss in right eye.

RESULTS

Pigmented lesions were observed along the arcades without peripheral retinal involvement. Intraretinal cystoid spaces, retinal neovascularization of posterior pole and severe peripheral and posterior retinal vasculitis were found on clinical examination and multimodal imaging. Based on characteristic clinical and electroretinographic findings, a diagnosis of ESCS was made.

CONCLUSION

This case highlights novel associations of retinal neovascularization and vasculitis with ESCS.

In vivo monitoring of mouse retinal temperature by ERG photoresponses

Non-damaging heating of the retina and RPE provides a promising treatment for retinal diseases. However, the lack of proper control over the temperature hinders the development of safe and repeatable procedures. Here, we demonstrate with mice a non-invasive method for estimating the temperature changes in the retina and the RPE during a heating procedure. The method is based on monitoring the temperature dependent properties of retinal photoresponses recorded by electroretinography (ERG). In this study, our aim was to investigate the feasibility of ERG signal for retinal temperature estimation, utilizing a-wave and b-wave kinetics as the source of temperature information. We quantified the temperature dependencies of photoresponse kinetics and developed two linear regression models between the temperature and the photoresponse features, enabling temperature estimation. With the first model, based on the a-wave of a single photoresponse, the RMS error obtained for retinal temperature estimation was <0.9 °C. The second model, applying the b-waves of five dim flash responses, an RMS error of <0.7 °C was achieved. In addition, we tested the sensitivity of the method to small changes in light stimulus strength and investigated suitable stimulus intervals for continuous retinal temperature monitoring. The proposed method provides a convenient technique for monitoring mouse retinal and RPE temperature with ERG recording when studying controlled retinal heating. Similar temperature dependencies exist in human ERG suggesting that this approach could also be applicable in clinical heating treatments.

Retinal degeneration rat model: A study on the structural and functional changes in the retina following injection of sodium iodate

Retinal disorders account for a large proportion of ocular disorders that can lead to visual impairment or blindness, and yet our limited knowledge in the pathogenesis and choice of appropriate animal models for new treatment modalities may contribute to ineffective therapies. Although genetic in vivo models are favored, the variable expressivity and penetrance of these heterogeneous disorders can cause difficulties in assessing potential treatments against retinal degeneration. Hence, an attractive alternative is to develop a chemically-induced model that is both cost-friendly and standardizable. Sodium iodate is an oxidative chemical that is used to simulate late stage retinitis pigmentosa and age-related macular degeneration. In this study, retinal degeneration was induced through systemic administration of sodium iodate (NaIO₃) at varying doses up to 80 mg/kg in Sprague-Dawley rats. An analysis on the visual response of the rats by electroretinography (ERG) showed a decrease in photoreceptor function with NaIO₃ administration at a dose of 40 mg/kg or greater. The results correlated with the TUNEL assay, which revealed signs of DNA damage throughout the retina. Histomorphological analysis also revealed extensive structural lesions throughout the outer retina and parts of the inner retina. Our results provided a detailed view of NaIO₃-induced retinal degeneration, and showed that the administration of 40 mg/kg NaIO₃ was sufficient to generate disturbances in retinal function. The pathological findings in this model reveal a degenerating retina, and can be further utilized to develop effective therapies for RPE, photoreceptor, and bipolar cell regeneration.

Protective effects of hydrogen gas in a rat model of branch retinal vein occlusion via decreasing VEGF-α expression

Background

Oxidative stress (OS) is an essential factor in the pathogenesis of branch retinal vein occlusion (BRVO). Studies have demonstrated the role of hydrogen gas in the regulation of OS. This study was designed to evaluate the efficacy of hydrogen gas on the BRVO rat model.

Methods

Twenty-four BRVO rats were randomly divided into two groups: the hydrogen gas (H) group (42% H₂, 21% O₂, 37% N₂) and the model (M) group (21% O₂, 79% N₂). Rats in the H group inhaled hydrogen gas for 8 h every day up to 30 d post-occlusion. Twelve age-matched healthy rats served as the control (C) group. Retinal function and morphology were detected at 1, 7, 14 and 30 d post-occlusion. Furthermore, the expression of vascular endothelial growth factor (VEGF-α) was detected by immunofluorescent staining.

Results

Full-field electroretinography (ffERG) revealed that the amplitude of the b-wave (dark-adaptation 3.0 response), the amplitude of the OPs2 wave and the light-adapted flicker response in the H group were all higher than those in the M group at 7 d post-occlusion (all p < 0.05). The reopen time of occlusive retinal vessels in the H group was 2.235 ± 1.128 d, which was shorter than that in the M group (4.234 ± 2.236 d, p < 0.05). The rats in the H group had a thinner IPL + GCL + NFL and an increased total retina compared with those in the M group at 3 d post-occlusion (p < 0.05), while the rats in the H group had a thicker INL, IPL + GCL + NFL and total retina compared with those at 7, 14 and 30 d post-occlusion (p < 0.05). Moreover, the flow velocity of ear vein blood was increased in the H group compared with that in the M group (p < 0.05). The expression of VEGF-α in the H group was dramatically decreased compared with that in the M group at 1, 7 and 14 d post-occlusion (p < 0.05), while the expression kept in similar level at 30 d post-occlusion (p > 0.05).

Conclusions

Our findings demonstrate that inhalation of hydrogen gas could alleviate retinal oedema, shorten reopen time and improve retinal function, and the potential mechanism might be related to a decrease in VEGF-α expression.

A case of X-linked retinoschisis with atypical fundus appearance

PURPOSE

Mutations in the RS1 gene are known to cause retinoschisis, an X-linked hereditary retinal degeneration. Here, we present a case of atypical retinoschisis with clinical findings of retinoschisis and retinitis pigmentosa.

METHODS

This report is an observational case report. The detailed ophthalmological examinations included visual field determination, multimodal imaging and electrophysiological recordings. Targeted next-generation sequencing of a retinal disease gene panel was performed.

RESULTS

The 55-year-old male, highly hyperopic patient, presented with a best-corrected Snellen visual acuity of 20/100 in the right eye and 20/400 in the left eye. In the kinetic visual field, there was a superior scotoma, as well as a ring scotoma in the inferior hemisphere in the right eye and a concentric visual field constriction to 10° in the left eye. Funduscopy revealed marked pigmentary changes (i.e. bone spicules) in the mid-periphery bilaterally and symmetrically, as well as two small intra-retinal haemorrhages in the left eye. Full-field electroretinography recordings showed extinguished rod and cone responses. Diagnostic-genetic testing revealed a hemizygous missense mutation in the RS1 gene (c.305G > A; p.Arg102Gln) was identified.

CONCLUSION

We present a case of atypical retinoschisis with clinical findings of retinitis pigmentosa.

Adaptation time, electroretinography, and pupillography in healthy subjects

PURPOSE

To investigate the relationship between adaptation time and the parameters of electroretinography (ERG) and pupillography in healthy subjects.

METHODS

Forty-six eyes of 23 healthy women (mean age 21.7 years) were enrolled. ERG and pupillography were tested in each of the right and left 23 eyes, respectively. ERG with a skin electrode was used to determine amplitude and implicit time by the records of rod-, flash-, cone-, and flicker-responses with white light (0.01-30 cd s/m²). Infrared pupillography was used to record the pupillary light reflex to 1-s stimulation of red light (100 cd/m²). Cone- and flicker- (rod-, flash- and pupil) responses were recorded after light (dark) adaptation at 1, 5, 10, 15, and 20 min.

RESULTS

Amplitude (µV) was significantly different between 1 min and ≥ 5 or ≥ 10 min after adaptation in b-wave of cone- or rod-response, respectively. Implicit time (ms) differed significantly between 1 min and ≥ 5 min after adaptation with b-wave of cone- and rod-response. There were significant differences between 1 min and ≥ 10 or ≥ 5 min after dark adaptation in parameter of minimum pupil diameter (mm) or constriction rate (%), respectively.

CONCLUSIONS

Cone-driven ERG can be recorded, even in 5 min of light adaptation time without any special light condition, whereas rod-driven ERG and pupillary response results can be obtained in 10 min or longer of dark adaptation time in complete darkness.

Enhanced S-cone syndrome: Clinical spectrum in Indian population

Purpose:

Enhanced S-cone syndrome (ESCS), a rare disorder, is often misdiagnosed as other forms of retinal degenerations, which have a poorer prognosis than ESCS. The aim of this study is to report the varied clinical features of ESCS and distinguish it from other similar disorders.

Methods:

We retrospectively scrutinized the records of patients with confirmed diagnosis of ESCS and analyzed the findings.

Results:

We included 14 patients (age range 4–39 years) who were confirmed to have ESCS according to pathognomonic electroretinography (ERG) showing reduced photopic, combined responses, and 30 Hz flicker with reduced L, M cone responses and supernormal S cone responses. The disease presented in the 1^st decade with night blindness and was almost stationary or minimally progressive. Mid-peripheral fundus changes in form of nummular pigmentary alterations, yellow punctate lesions, and macular schisis were noted. The vision ranged from 6/6 to 6/36 with follow-up ranging from 1month to 22 years.

Conclusion:

ESCS shows varied clinical features ranging from unremarkable fundus to pigment clumping and atrophic lesions. It has good prognosis with patients mostly maintaining their vision. ERG is diagnostic. More awareness and knowledge about this entity can help to differentiate it from other forms of night blindness.

Mesenchymal stem cell-derived extracellular vesicles and retinal ischemia-reperfusion

Retinal ischemia is a major cause of vision loss and impairment and a common underlying mechanism associated with diseases such as glaucoma, diabetic retinopathy, and central retinal artery occlusion. The regenerative capacity of the diseased human retina is limited. Our previous studies have shown the neuroprotective effects of intravitreal injection of mesenchymal stem cells (MSC) and MSC-conditioned medium in retinal ischemia in rats. Based upon the hypothesis that the neuroprotective effects of MSCs and conditioned medium are largely mediated by extracellular vesicles (EVs), MSC derived EVs were tested in an in-vitro oxygen-glucose deprivation (OGD) model of retinal ischemia. Treatment of R28 retinal cells with MSC-derived EVs significantly reduced cell death and attenuated loss of cell proliferation. Mechanistic studies on the mode of EV endocytosis by retinal cells were performed in vitro. EV endocytosis was dose- and temperature-dependent, saturable, and occurred via cell surface heparin sulfate proteoglycans mediated by the caveolar endocytic pathway. The administration of MSC-EVs into the vitreous humor 24 h after retinal ischemia in a rat model significantly enhanced functional recovery, and decreased neuro-inflammation and apoptosis. EVs were taken up by retinal neurons, retinal ganglion cells, and microglia. They were present in the vitreous humor for four weeks after intravitreal administration, with saturable binding to vitreous humor components. Overall, this study highlights the potential of MSC-EV as biomaterials for neuroprotective and regenerative therapy in retinal disorders.

Cannabis use and human retina: The path for the study of brain synaptic transmission dysfunctions in cannabis users

Owing to the difficulty of obtaining direct access to the functioning brain, new approaches are needed for the indirect exploration of brain disorders in neuroscience research. Due to its embryonic origin, the retina is part of the central nervous system and is well suited to the investigation of neurological functions in psychiatric and addictive disorders. In this review, we focus on cannabis use, which is a crucial public health challenge, since cannabis is one of the most widely used addictive drugs in industrialized countries. We first explain why studying retinal function is relevant when exploring the effects of cannabis use on brain function. Next, we describe both the retinal electrophysiological measurements and retinal dysfunctions observed after acute and regular cannabis use. We then discuss how these retinal dysfunctions may inform brain synaptic transmission abnormalities. Finally, we present various directions for future research on the neurotoxic effects of cannabis use.

Hypotrichosis with cone-rod dystrophy in a patient with cadherin 3 (CDH3) mutation

PURPOSE

To investigate a very rare case of hypotrichosis with cone-rod dystrophy caused by a P-cadherin CDH3 mutation.

METHODS

A 16-year-old Syrian girl was examined at age 9 and 14 years with an ophthalmological examination, fundus imaging, OCT and electrophysiological recordings (ERG and PERG). A disease-targeted gene panel sequencing was performed.

RESULTS

Fundus images showed pigmentations at the posterior eye pole to the mid periphery, as well as vessel tortuosity. OCT images revealed a loss of the outer retinal segments and IS/OS in the central macula. The scotopic and photopic ERGs showed moderately reduced amplitudes at age 9 years that became severely reduced at age of 14 years. The PERG was undetectable at age 9 years. In color vision testing, protan-deutan confusion errors occurred. Gene panel analysis revealed one homozygous mutation in CDH3 (c.1508G>A; p.Arg503His).

CONCLUSION

This case shows that a CDH3 mutation besides macula dystrophy can cause widespread cone-rod dystrophy with hypotrichosis without any other pathology besides hypoplastic nails. This points to a common pathway of hair growth and photoreceptor development that can be disturbed by a CDH3 mutation (c.1508G>A; p.Arg503His) located in the EC4 repeat region of the gene.

Sildenafil Administration in Dogs Heterozygous for a Functional Null Mutation in Pde6a: Suppressed Rod-Mediated ERG Responses and Apparent Retinal Outer Nuclear Layer Thinning

This study was designed to assess risk for retinal toxicity associated with administration of high-dose sildenafil citrate to dogs heterozygous for a functionally null mutation in Pde6a over a 4-month period. Three Pde6a +/- dogs were administered 14.3 mg/kg sildenafil per os and two Pde6a +/- dogs placebo once daily for 16 weeks. Three Pde6a +/+ dogs were administered sildenafil for 7 days. Ophthalmic examination, vision testing, and electroretinography (ERG) were regularly performed. At study termination, dogs were euthanized and globes collected. Retinal layer thickness and photoreceptor nuclei counts were determined from plastic sections. In both Pde6a +/- and Pde6a +/+ sildenafil-treated (ST) dogs, elevation of dark-adapted b-wave threshold and unmasking of the scotopic threshold response (STR) were observed. Sildenafil treated Pde6a +/- dogs had significantly thinner ONL (24.90 +/-1.88 μm, p = 0.004) and lower photoreceptor nuclei counts (273.6 +/- 29.3 cells/100 μm, p = 0.008) compared to measurements (35.90 +/- 1.63 μm) and counts (391.5 +/-27.0 cells/100 μm) from archived untreated Pde6a +/- dogs.

The complexation of steroid hormones into cyclodextrin alters the toxic effects on the biological parameters of zebrafish (Danio rerio)

The objective of this study was to evaluate the toxic effects of progesterone (P₄F) and estradiol (E₂F) and the effect of these steroid hormones complexed into cyclodextrins, commercially available drugs, such as micronized progesterone (P₄M) and transdermal estradiol (E₂T), and evaluate them as endocrine disruptors through biological parameters of Danio rerio. An acute toxicity test was performed with hormones using D. rerio embryos according to OECD 236 guidelines. The heart rate, mortality, and teratogenic effects were evaluated. In addition, a chronic toxicity test was assayed with adult animals for evaluation of animal behavior, reproductive capacity, and electrophysiological responses of the retina. Analysis of the results of the acute toxicity test with embryos exposed to progestins and estrogens showed that free hormones caused a higher percentage of teratogenic effects such as pericardial edema, yolk sac edema, and spinal deformation. Behavioral evaluation (30-60 days) of adult animals exposed to P₄M, E₂F, and E₂T demonstrated higher frequencies of aggressive behaviors such as Chase away, Persecution, Escape, and Attack. Analysis of reproductive capacity did not show significant differences in the number of viable eggs, and no significant changes were observed in the electrophysiological responses of the retina. According to these results, there is a higher toxicity effect of hormones in the free form when compared to the commercial forms and inclusion complexes. This indicates that complexation into cyclodextrin reduced the toxicity of the hormones according to the parameters studied.