The multifocal electroretinogram

Evaluation of Structural and Functional Retinal Changes in Children With Intermittent Exotropia Versus Healthy Children

PURPOSE

To detect structural and functional changes in children with intermittent exotropia using optical coherence tomography, pattern electroretinography (ERG), and multifocal ERG.

METHODS

The study included 26 patients with intermittent exotropia and 26 healthy individuals matched for age and sex with a mean age of 9.23 and 11.20 years in the intermittent exotropia and control groups, respectively (P = .310). All patients underwent full ophthalmic examination including measurement of the angle of strabismus at near and far, and assessment of the macula and optic nerve using optical coherence tomography, pattern ERG, and multifocal ERG.

RESULTS

All patients had 6/6 best corrected visual acuity with no fixation preference. A significantly prolonged P and N wave latency was found in all measured rings of multifocal ERG of patients with intermittent exotropia, P wave amplitude was lower in rings 1 and 5, and N wave amplitude was lower in rings 1 and 2. Regarding pattern ERG, the amplitude of P50 wave was lower and N95 latency was prolonged in the intermittent exotropia group. The upper and lower ganglion cell complex and the superior retinal nerve fiber layer were significantly thinner in the intermittent exotropia group compared to controls.

CONCLUSIONS

Children with intermittent exotropia without any associated amblyopia or refractive error showed a subnormal pattern and multifocal ERG response in addition to a thinner ganglion cell layer and retinal nerve fiber layer compared to normal controls. This signifies that subtle structural and functional retinal changes are found in patients with intermittent exotropia. [J Pediatr Ophthalmol Strabismus. 2024;61(5):317-324.].

Optical Assessment of Photoreceptor Function Over the Macula

Purpose

The purpose of this study was to develop next-generation functional photoreceptor imaging using ultrahigh-speed swept-source optical coherence tomography (UHS-SS-OCT) and split-spectrum amplitude-decorrelation optoretinography (SSADOR) algorithm. The advancement enables rapid surveying of large retinal areas, promising non-contact, objective, and quantifiable measurements of macular visual function.

Methods

We designed and built a UHS-SS-OCT prototype instrument using a wavelength tunable laser with 1 MHz A-scan rate. The functional scanning protocol records 5 repeated volumes in 3 seconds. A flash pattern selectively exposes the imaged retina area. SSADOR quantifies photoreceptor light response by extracting optical coherence tomography (OCT) signal changes within the photoreceptor outer segment before and after the flash.

Results

The study prospectively enrolled 16 eyes from 8 subjects, demonstrating the ability to measure photoreceptor light response over a record field of view (3 × 3 mm2) with high topographical resolution (approximately 100 µm). The measured SSADOR signal corresponds to the flashed pattern, whose amplitude also correlates with flash strength, showing consistency and reproducibility across subjects.

Conclusions

The integration of high-performance UHS-SS-OCT and SSADOR enables characterizing photoreceptor function over a clinically meaningful field of view, while maintaining a workflow that can be integrated into routine clinical tests and trials. The new approach allows detecting changes in photoreceptor light response with high sensitivity and can detect small focal impairments.

Translational Relevance

This innovative advance can enable us to detect early photoreceptor abnormalities, as well as help to stage and monitor degenerative retinal diseases, potentially providing a surrogate visual function marker for retinal diseases and accelerating therapeutic development through a safe and efficient outcome endpoint.

Function and Circulation of the Retina and Choroid in Case of Indolent Nonprogressive Multifocal Choroidal Lesions

Indolent nonprogressive multifocal choroidal lesions have been reported to be benign choroidal lymphatic lesions that do not affect the visual function. However, as best known, there are no reports on whether these lesions affect the circulation and function of the retina and choroid. We report a case of indolent nonprogressive multifocal choroidal lesions in which retinal images were available to assess the retinal and choroidal circulation and whether it impacted the retinal function. The patient was a 45-year-old man. Swept-source optical coherence tomography (OCT) showed multiple well-defined, uniform, hyporeflective cavernous lesions in the choroidal layer. Then a diagnosis of indolent nonprogressive multifocal choroidal lesions was made based on the similarity of the features with those reported. OCT angiography showed no blood flow signals in the lesions and reduced blood flow signals in the choroid and choriocapillaris directly above the lesions. Fundus autofluorescence showed retinal pigment epithelial damages that were colocalized with the choroidal lesions. We then performed static visual field testing and multifocal electroretinography (mfERG). The static visual field test showed no decrease in sensitivity in the entire visual field, and mfERG showed no decrease in the amplitudes or implicit times indicating normal retinal function. In indolent nonprogressive multifocal choroidal lesions, the photoreceptor function is preserved but a mild retinal pigment epithelium disorder is present. Thus, the follow-up examinations of indolent nonprogressive multifocal choroidal lesions should include retinal function tests.

Additional measures of macular function beyond visual acuity

PURPOSE

Visual function is a complex process in which external visual stimuli are interpreted. Patients with retinal diseases and prolonged follow-up times may experience changes in their visual function that are not detected by the standard visual acuity measure, as they are a result of other alterations in visual function. With the advancement of different methods to evaluate visual function, additional measurements have become available, and further standardization suggests that some methods may be promising for use in clinical trials or routine clinical practice. The objectives of this article are to review these additional measurements and to provide guidance on their application.

METHODS

The Vision Academy's membership of international retinal disease experts reviewed the literature and developed consensus recommendations for the application of additional measures of visual function in routine clinical practice or clinical trials.

RESULTS

Measures such as low-luminance visual acuity, contrast sensitivity, retinal fixation and microperimetry, and reading performance are measures which can complement visual acuity measurements to provide an assessment of overall visual function, including impact on patients' quality of life. Measures such as dark adaptation, color vision testing, binocular vision testing, visual recognition testing, and shape discrimination require further optimization and validation before they can be implemented in everyday clinical practice.

CONCLUSION

Additional measurements of visual function may help identify patients who could benefit from earlier diagnosis, detection of disease progression, and therapeutic intervention. New and additional functional clinical trial endpoints are required to fully understand the early stages of macular disease, its progression, and the response to treatment.

[Multifocal electroretinography in the diagnosis and monitoring of early and intermediate stages of age-related macular degeneration]

Multifocal electroretinography is a valuable diagnostic method for the objective localization and quantitative assessment of functional disorders of the central retina in age-related macular degeneration. It is used to detect early changes, monitor the course of the disease and treatment outcomes. In many cases, multifocal electroretinography is a more sensitive method for detecting functional disorders at the early/intermediate stage of age-related macular degeneration compared to morphological (optical coherence tomography) and subjective (visual acuity, perimetry) testing methods.

Endpoints for clinical trials in ophthalmology

With the identification of novel targets, the number of interventional clinical trials in ophthalmology has increased. Visual acuity has for a long time been considered the gold standard endpoint for clinical trials, but in the recent years it became evident that other endpoints are required for many indications including geographic atrophy and inherited retinal disease. In glaucoma the currently available drugs were approved based on their IOP lowering capacity. Some recent findings do, however, indicate that at the same level of IOP reduction, not all drugs have the same effect on visual field progression. For neuroprotection trials in glaucoma, novel surrogate endpoints are required, which may either include functional or structural parameters or a combination of both. A number of potential surrogate endpoints for ophthalmology clinical trials have been identified, but their validation is complicated and requires solid scientific evidence. In this article we summarize candidates for clinical endpoints in ophthalmology with a focus on retinal disease and glaucoma. Functional and structural biomarkers, as well as quality of life measures are discussed, and their potential to serve as endpoints in pivotal trials is critically evaluated.

Effects of Smoothing and Adaptive Filtering in Multifocal Electroretinography (mfERG)

(1) Background: mfERG testing is used to study the function of cone photoreceptors in the central retina. Various filters including "smoothing" (Smooth) and "adaptive data filtering" (Adapt) are used to simplify raw data. This study will seek to characterize the effect of data modification on raw patient data. (2) Methods: This was a retrospective study of patients with mfERG results at our institution. For each patient, raw mfERG data without filtering, with smooth level 4 modifier applied, and with adapt level 4 applied were collected and compared. (4) Conclusions: In all patients, smoothing and adaptive filter modifiers create statistically significant differences in both P1 latency and P1 amplitude values when compared to raw data. The impacts of these filters demonstrated in this study should impact physicians' decision making when interpreting mfERG results.

Retinitis Pigmentosa: Current Clinical Management and Emerging Therapies

Retinitis pigmentosa (RP) comprises a group of inherited retinal dystrophies characterized by the degeneration of rod photoreceptors, followed by the degeneration of cone photoreceptors. As a result of photoreceptor degeneration, affected individuals experience gradual loss of visual function, with primary symptoms of progressive nyctalopia, constricted visual fields and, ultimately, central vision loss. The onset, severity and clinical course of RP shows great variability and unpredictability, with most patients already experiencing some degree of visual disability in childhood. While RP is currently untreatable for the majority of patients, significant efforts have been made in the development of genetic therapies, which offer new hope for treatment for patients affected by inherited retinal dystrophies. In this exciting era of emerging gene therapies, it remains imperative to continue supporting patients with RP using all available options to manage their condition. Patients with RP experience a wide variety of physical, mental and social-emotional difficulties during their lifetime, of which some require timely intervention. This review aims to familiarize readers with clinical management options that are currently available for patients with RP.

Modeling of dielectric resonator antenna array for retina photoreceptors

The retina encompasses several cone and rod photoreceptors at fovea region i.e., 90 million cells of rod photoreceptors and 4.5million cells of cone photoreceptors. The overall photoreceptors determine the vision of every human. An electromagnetic dielectric resonator antenna has been presented for retina photoreceptors in order to model them at fovea and its peripheral retina with the respected angular spectrum. Three coloring primary system of human eye (R, G, B) can be realized based on the model. Three miscellaneous models i.e., simple, graphene coated, and interdigital models have been presented in this paper. The nonlinear property of interdigital structures is one of the best advantages to use for creating the capacitor. The capacitance property helps improving the upper band of visible spectrum. The absorption of light for graphene as an energy harvesting material and its conversion into electrochemical signals is making it one of the best models. The mentioned three electromagnetic models of human photoreceptors have been expressed as a receiver antenna. The proposed electromagnetic models based on dielectric resonator antenna (DRA) are being analyzed for cones and rods photoreceptors of retina in the human eye by Finite Integral Method (FIM) utilized by CST MWS. The results show that the models are so fine for vision spectrum due to its localized near field enhancement property. The results indicate fine parameters of S 11 (return loss below -10 dB) with invaluable resonants in a wide range of frequencies from 405 THz to 790 THz (vision spectrum), appropriate S 21 (insertion loss 3-dB bandwidth), very good field distribution of electric and magnetic fields for flowing the power and electrochemical signals. Finally, mfERG clinical and experimental results validate the numeric results by the normalized output to input ratio of these models and it points out that these models can stimulate the electrochemical signals in photoreceptor cells for the best suiting of realizing the new retinal implants.

Comparison of DTL and gold cup skin electrodes for recordings of the multifocal electroretinogram

OBJECTIVE

To compare mfERG recordings with the Dawson-Trick-Litzkow (DTL) and gold cup skin electrode in healthy young and old adults and to test the sensitivity of both electrodes to age-related changes in the responses.

METHODS

Twenty participants aged 20-27 years ("young") and 20 participants aged 60-75 ("old") with a visual acuity of ≤ 0 logMAR were included. The mfERG responses were recorded simultaneously using DTL and skin electrodes. P1 amplitudes, peak times and signal-to-noise ratios (SNRs) were compared between both electrodes and across age groups, and correlation analyses were performed. The electrode's performance in discriminating between age groups was assessed via area under curve (AUC) of receiver operating characteristics.

RESULTS

Both electrodes reflected the typical waveform of mfERG recordings. For the skin electrode, however, P1 amplitudes were significantly reduced (p < 0.001; reduction by over 70%), P1 peak times were significantly shorter (p < 0.001; by approx. 1.5 ms), and SNRs were reduced [(p < 0.001; logSNR ± SEM DTL young (old) vs gold cup: 0.79 ± 0.13 (0.71 ± 0.15) vs 0.37 ± 0.15 (0.34 ± 0.13)]. All mfERG components showed strong significant correlations (R² ≥ 0.253, p < 0.001) between both electrodes for all eccentricities. Both electrodes allowed for the identification of age-related P1 changes, i.e., P1-amplitude reduction and peak-time delay in the older group. There was a trend to higher AUC for the DTL electrode to delineate these differences between age groups, which, however, failed to reach statistical significance.

CONCLUSIONS

Both electrode types enable successful mfERG recordings. However, in compliant patients, the use of the DTL electrode appears preferable due to the larger amplitudes, higher signal-to-noise ratio and its better reflection of physiological changes, i.e., age effects. Nevertheless, skin electrodes appear a viable alternative for mfERG recordings in patients in whom the use of corneal electrodes is precluded, e.g., children and disabled patients.

Retinal Neurodegeneration in Euglycemic Hyperinsulinemia, Prediabetes, and Diabetes

Diabetic retinopathy (DR) is a challenging public health problem mainly because of its growing prevalence and risk of blindness. In general, our current knowledge and practice have failed to prevent the onset or progression of DR to sight-threatening complications. While there are treatment options for sight-threatening complications of DR, it is crucial to pay more attention to the early stages of DR to decrease its prevalence. Growing evidence suggests many pathologic changes occur before clinical presentations of DR in euglycemic hyperinsulinemia, prediabetes, and diabetes. These pathological changes occur in retinal neurons, glia, and microvasculature. A new focus on these preclinical pathologies - especially on hyperinsulinemia - may provide further insight into disease mechanisms, endpoints for clinical trials, and druggable targets in early disease. Here, we review the current evidence on the pathophysiological changes reported in preclinical DR and appraise preventive and treatment options for DR.

Electrophysiological and anatomical outcomes of subthreshold micropulse laser therapy in chronic central serous chorioretinopathy

BACKGROUND

To evaluate short-term efficacy of subthreshold micropulse laser therapy on chronic central serous chorioretinopathy (CSC) electrophysiologically and anatomically.

METHODS

This prospective study included 18 eyes with chronic CSC. Subthreshold micropulse laser therapy was applied to the eyes using Endpoint Management System (EpM). The efficacy of the treatment was evaluated with optical coherence tomography (OCT) and multifocal electroretinography (mfERG) measurements before and after one month of the treatment.

RESULTS

The mean patient age was 47.3 ± 5.7 years (ranged between 36 and 56). The mean symptomatic time of the disease was 12.7 ± 3.33 months. Central macular thickness, choroidal thickness, subretinal fluid height and width showed statistically significant decreases after EpM treatment (p < 0.05). P 1 amplitude of ring 1, 3, 4, and 5 in mfERG increased significantly (p <  0.05).

CONCLUSIONS

The study demonstrated that, in both OCT and electrophysiological evaluations, EpM subthreshold laser therapy resulted in anatomical and functional improvements in chronic CSC.

Graphene coated dielectric resonator antenna for modeling the photoreceptors at visible spectrum

The absorption of light is very important task for retina photoreceptors. Graphene is an energy harvesting material and one of the best models for the electromagnetic wave absorption and its conversion into signals. In this paper, an electromagnetic modeling of human retinal photoreceptors has been presented based on graphene coated material as a receiver antenna. The proposed electromagnetic model based on dielectric resonator antenna (DRA) is being analyzed for retina photoreceptors of human eye (cones and rods) by Finite Integral Method (FIM) collaborated with CST MWS. The results show that the model is good for vision spectrum with a proper field enhancement in cone photoreceptor due to its sensitivity to light. The results indicate proper S₁₁ (return loss below −10 dB) with invaluable resonances in a wide range of frequencies from 405 THz to 790 THz (vision spectrum), suitable S₂₁ (insertion loss 3-dB bandwidth), very good field distribution for flowing the power within desired radiation characteristics. The drawbacks of conventional model (no coating) have been resolved by presenting this one at blue spectrum specifically. Finally, mfERG clinical and experimental results show that this model can stimulate the electrochemical voltages and currents in photoreceptor cells.

The relation of the multifocal electroretinographic response to macular layer volume

PURPOSE

To determine the association of the multifocal electroretinographic (mfERG) response amplitude with the volumes of the inner, postreceptor, and photoreceptor retinal layers in the region stimulated by each mfERG element.

METHODS

Sixteen healthy, young adult control subjects were studied. Each of the 103 hexagonal elements of the standard, scaled mfERG were aligned, where possible, with patches of retina imaged using optical coherence tomography. Stimuli falling on the fovea and on the optic nerve head were excluded. Linear mixed-effects modeling was then used to derive estimated coefficients (voltage/volume) for the mfERG response throughout the full 80 ms standard epoch. The resulting predicted response amplitudes originating in each layer were then compared to pharmacologically "dissected" mfERGs obtained from other studies in monkey eyes.

RESULTS

Across the duration of the response, the amplitude of the modeled contribution from (1) the inner retina was small-to-modest, (2) the postreceptor retina was larger and contained two prominent peaks, and (3) the photoreceptor response was the largest and most closely paralleled the overall (i.e., intact) response, including late-appearing oscillations. The significance of each layer's contribution was greatest when the absolute amplitude of that layer's response was largest. The contribution of the inner retina was maximally significant in the interval between the prominent troughs and peaks of the intact response. The contributions of the postreceptor and photoreceptor responses were maximally significant at the prominent troughs and peaks of the intact response.

CONCLUSIONS

The results of the model were in good overall agreement with previous interpretations of the cellular contributions to the mfERG. There was also fair agreement with pharmacologically dissected monkey mfERG responses. Thus, the estimations of the contributions of the retinal layers to the mfERG so produced appeared plausible.

The Influence of Coronary Heart Disease on Retinal Electrophysiological Examination (Full-field, Pattern and Multifocal Electroretinograms)

PURPOSE

To evaluate the influence of coronary heart disease (CHD) on retinal function using a battery of electrophysiological measures.

MATERIALS AND METHODS

We conducted a prospective pilot study comparing 34 patients with a confirmed diagnosis of CHD with 21 healthy participants. Further inclusion criteria were a decimal visual acuity (VA) of 0.8 or better and patient age between 40 and 80 years. All participants were divided into three groups according to the severity of CHD (1, 2 or 3 vessels involved) and one healthy control group. Testing was performed on one eye per patient, either selecting the eye with higher VA or, when equal, selecting randomly. The test procedure consisted of a pattern electroretinogram (ERG), a full-field ERG, a multifocal ERG and an ophthalmic screening examination.

RESULTS

Implicit times of the b-wave measured using scotopic full-field ERG were significantly prolonged in all CHD patient groups (p < .000). Thus, full-field ERG allowed clinicians to differentiate between healthy patients and those suffering from CHD. The multifocal ERG showed significantly different results concerning the amplitude density (p < .008) in each patient group compared with the control group. CHD had a significant impact on cone-pathway function, although the severity of CHD did not correlate with functional deficiencies of cone cells.

CONCLUSIONS

Confirmed coronary vascular diseases are correlated with macular cone and bipolar cell function, which can be detected by measuring electrophysiological retinal signals.

Role of pattern electroretinogram in assessment of retinal dysfunction in hypertensive patients

BACKGROUND

Hypertension is a major health problem in both developing and developed countries. Hypertension causes retinal structural and functional impairment within the ganglion cell layer. Pattern electroretinogram (PERG) offers an objective simple tool for assessment of retinal ganglion cell function.Aim of the work: To assess retinal dysfunction in hypertensive patients with or without signs of retinopathy using PERG.

MATERIALS AND METHODS

This is a case control study, including ninety-eight eyes. Twenty-eight eyes of healthy subjects served as a control group (group I) and seventy eyes of patients with systemic hypertension, who were further subdivided into group II including 39 eyes of hypertensive patients with normal fundus and group III including 31 eyes of patients with signs of hypertensive retinopathy. All subjects were subjected to ophthalmological examination and electrophysiological assessment using PERG.

RESULTS

PERG implicit times were significantly prolonged and amplitudes were significantly reduced in patients with established hypertensive retinopathy. PERG abnormalities were detected in 96.8% of hypertensive retinopathy patients and 79.5% of hypertensive patients with normal fundus.

CONCLUSIONS

PERG can objectively assess retinal dysfunction in hypertensive patients and may be considered a promising tool for early detection of hypertensive retinopathy.

A Systematic Review of Carotenoids in the Management of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) remains a leading cause of modifiable vision loss in older adults. Chronic oxidative injury and compromised antioxidant defenses represent essential drivers in the development of retinal neurodegeneration. Overwhelming free radical species formation results in mitochondrial dysfunction, as well as cellular and metabolic imbalance, which becomes exacerbated with increasing age. Thus, the depletion of systemic antioxidant capacity further proliferates oxidative stress in AMD-affected eyes, resulting in loss of photoreceptors, neuroinflammation, and ultimately atrophy within the retinal tissue. The aim of this systematic review is to examine the neuroprotective potential of the xanthophyll carotenoids lutein, zeaxanthin, and meso-zeaxanthin on retinal neurodegeneration for the purpose of adjunctive nutraceutical strategy in the management of AMD. A comprehensive literature review was performed to retrieve 55 eligible publications, using four database searches from PubMed, Embase, Cochrane Library, and the Web of Science. Epidemiology studies indicated an enhanced risk reduction against late AMD with greater dietary consumption of carotenoids, meanwhile greater concentrations in macular pigment demonstrated significant improvements in visual function among AMD patients. Collectively, evidence strongly suggests that carotenoid vitamin therapies offer remarkable synergic protection in the neurosensory retina, with the potential to serve as adjunctive nutraceutical therapy in the management of established AMD, albeit these benefits may vary among different stages of disease.

Effectiveness of Microcurrent Stimulation in Preserving Retinal Function of Blind Leading Retinal Degeneration and Optic Neuropathy: A Systematic Review

OBJECTIVES

To systematically identify and summarize the effectiveness and the parameters of electrical stimulation (ES) for the preservation of visual function in major retinal degeneration and optic neuropathy.

MATERIALS AND METHODS

A systematic review of clinical studies, using ES therapy in patients with blind leading retinal degenerations, including retinitis pigmentosa (RP), age-related macular degeneration (AMD), glaucoma, retinal vein occlusion (RVO), retinal artery occlusion (RAO), and optic neuropathy was conducted. PubMed, EMBASE, Cochrane Library, and Web of Science were searched for relevant interventional studies including randomized controlled trials (RCTs) and observational studies.

RESULTS

A total of 10 RCTs and 15 observational studies were included. Transcorneal ES (TcES), transpalpebral ES (TpES), transdermal ES (TdES), and repetitive transorbital alternating current stimulation (rtACS) were used for the treatment of the patients. ES using 20 Hz biphasic pulses with current strength at 150%-200% of individual electrical phosphene threshold (EPT) for RP patients showed improved retinal function detected by visual acuity (VA), visual field (VF), or electrical retinal graphs (ERG). rtACS on patients with optic neuropathy showed significant preservation of VA and VF. Clinical studies on AMD, RAO, and glaucoma indicated promising protective effects of ES on the visual function, though the amount of evidence is limited.

CONCLUSIONS

ES treatment has promising therapeutic effects on RP and optic neuropathy. More large-scale RCT studies should be conducted to elucidate the potential of ES, especially on AMD, RAO, and glaucoma. A comparison of the effects by different ES methods in the same disease populations is still lacking. Parameters of the electric current and sensitive detection method should be optimized for the evaluation of ES treatment effects in future studies.

An insight on the anatomical and functional consequences of aflibercept therapy in age-related macular degeneration

BACKGROUND

Evaluation of anatomical and functional recovery of the retina after aflibercept therapy in neovascular age-related macular degeneration.

MATERIALS AND METHODS

This prospective study enrolled 33 eyes of 33 naive age-related macular degeneration patients with an average age of 69 (55-82) years. Following a thorough ophthalmological examination, baseline color fundus photography, optical coherence tomography and fluorescein angiography were used to assess the angiographic characteristics and classification of the lesions. Multifocal electroretinography and microperimetry were recorded. In the first three months, all patients received three consecutive intravitreal aflibercept injections on a monthly basis. After the initial three doses, non-responders received additional afibercept injections. The baseline, 3rd and 6th month data were recorded for analysis.

RESULTS

The baseline average best-corrected visual acuity (1.05 log MAR) improved dramatically to 0.9 log MAR in the 3rd and 6th months, respectively. The baseline average central macular thickness of 358.5 ± 232.1 μm decreased significantly to 273.0 ± 109.9 μm and 245.5 ± 109.3 μm in the 3rd and 6th months, respectively. The average thickness of the central 1 mm macular region decreased significantly from 349.5 ± 96.4 μm to the 3rd and 6th month values of 320.6 ± 101.9 and 290.5 ± 86.4 μm, respectively. While the mean retinal sensitivity increased significantly from 4.7 ± 3.0 dB to 6.9 ± 3.4 Db, local deficit decreased from -11.6 ± 4.6 dB to -9.4 ± 4.6 dB. Significant improvements were also observed in all rings of N1 and P1 waves.

CONCLUSION

Intravitreal aflibercept therapy resulted in significant morphological improvements that were easily identifiable during the 3rd month. Electrophysiological improvements were delayed only to become statistically significant in the 6th month. However, it has been shown that visual acuity and optical coherence tomography parameters alone may be insufficient for both the morphological and functional assessment of the retina.

Fundus motion during mfERG testing

PURPOSE

The purpose of this study was to assess eye movements during a multifocal ERG (mfERG) recording. This study evaluated the relationship between bivariate contour ellipse areas (BCEAs), mfERG amplitudes (Amps) and mfERG implicit times (ITs) with repeat testing and experienced subjects.

METHODS

Thirty subjects were selected (15 experienced to ocular procedures and 15 novices). All were confirmed to have healthy retinas and at least 20/25 vision. MfERGs with a stimulus near 100% contrast and 4-min m-sequence were recorded on two different days using our common clinical technique, which did not constrain the head. VERIS with fundus monitoring system was used for recording with a Burian-Allen electrode. An external camera captured the fundus during each mfERG recording. The optic nerve head position was tracked in each video using a custom algorithm in order to determine BCEAs. Each subject performed one mfERG on two different days. MfERGs were analyzed for Amps and ITs for the fovea and whole eye.

RESULTS

There was no correlation between the mfERG metrics and BCEAs with repeat testing. There were also no differences between the experienced and novice subjects for mfERG Amps, ITs or BCEAs. Eye movements between visits were highly correlated (multiple r = 0.67). BCEAs were larger during mfERGs (1.04 ± 0.8 deg²) than those observed in previous literature using brief viewing tasks (< 0.3 deg²). The proportion of time spent fixating within 1.0 and 2.0 degrees of the central hexagon was 68 and 93%, respectively.

CONCLUSIONS

This study is the first to evaluate the stability of the retina while recording a mfERG in healthy subjects and indicates that the center of fixation during a mfERG stays within the central hexagon. Eye stability during an initial recording is the best indicator of stability on the second recording. The amount of movement during these recordings did not seem to affect the mfERG Amps or ITs. These data suggest clinical confidence with mfERGs when recording novice patients.

Looking Ahead: Visual and Anatomical Endpoints in Future Trials of Diabetic Macular Ischemia

Diabetic macular ischemia (DMI) is a common complication of diabetic retinopathy that can lead to progressive and irreversible visual loss. Despite substantial clinical burden, there are no treatments for DMI, no validated clinical trial endpoints, and few clinical trials focusing on DMI. Therefore, generating consensus on validated endpoints that can be used in DMI for the development of effective interventions is vital. In this review, we discuss potential endpoints appropriate for use in clinical trials of DMI, and consider the data required to establish acceptable and meaningful endpoints. A combination of anatomical, functional, and patient-reported outcome measures will provide the most complete picture of changes that occur during the progression of DMI. Potential endpoint measures include change in size of the foveal avascular zone measured by optical coherence tomography angiography and change over time in best-corrected visual acuity. However, these endpoints must be supported by further research. We also recommend studies to investigate the natural history and progression of DMI. In addition to improving understanding of how patient demographics and comorbidities such as diabetic macular edema affect clinical trial endpoints, these studies would help to build the consensus definition of DMI that is currently missing from clinical practice and research.

Role of multifocal electroretinogram in assessment of early retinal dysfunction in hypertensive patients

PURPOSE

To investigate localized retinal dysfunction in hypertensive patients using multifocal electroretinogram (mfERG) and to assess its sensitivity as an early predictor for the development of retinopathy in hypertensive patients.

METHODS

Ninety-eight eyes were included in this case-control study. Twenty-eight eyes of healthy subjects served as a control group (group I). Seventy eyes belonged to patients with systemic hypertension assigned into two groups; group II including 39 eyes of hypertensive patients with normal fundus and group III including 31 eyes of patients with signs of hypertensive retinopathy. All participants were subjected to complete ophthalmic and electrophysiological examination using mfERG. N1 and P1 wave amplitudes and implicit times from the central hexagon and four concentric rings across the visual field were analyzed.

RESULTS

mfERG amplitudes were significantly reduced in hypertensive group with retinopathy than in controls. N1 amplitude was significantly reduced in the most eccentric ring in eyes of hypertensive patients with normal fundus.

CONCLUSION

mfERG is a sensitive objective tool for assessment of retinal dysfunction in hypertensive patients. mfERG amplitude is a promising predictor for early development of retinopathy in systemic hypertension.

Management of retinitis pigmentosa by Wharton's jelly derived mesenchymal stem cells: preliminary clinical results

PURPOSE

The aim of this study is to determine if umbilical cord Wharton's jelly derived mesenchymal stem cells implanted in sub-tenon space have beneficial effects on visual functions in retinitis pigmentosa patients by reactivating the degenerated photoreceptors in dormant phase.

MATERIAL AND METHODS

This prospective, open-label, phase-3 clinical trial was conducted between April of 2019 and October of 2019 at Ankara University Faculty of Medicine, Department of Ophthalmology. 32 RP patients (34 eyes) were included in the study. The patients were followed for 6 months after the Wharton's jelly derived mesenchymal stem cell administration, and evaluated with consecutive examinations. All patients underwent a complete routine ophthalmic examination, and best corrected visual acuity, optical coherens tomography angiography, visual field, multifocal and full-field electroretinography were performed. The quantitative results were obtained from a comparison of the pre-injection and final examination (6th month) values.

RESULTS

The mean best corrected visual acuity was 70.5 letters prior to Wharton's jelly derived mesenchymal stem cell application and 80.6 letters at the 6th month (p = 0.01). The mean visual field median deviation value was 27.3 dB before the treatment and 24.7 dB at the 6th month (p = 0.01). The mean outer retinal thickness was 100.3 μm before the treatment and 119.1 μm at 6th month (p = 0.01). In the multifocal electroretinography results, P1 amplitudes improved in ring1 from 24.8 to 39.8 nv/deg2 (p = 0.01), in ring2 from 6.8 to 13.6 nv/deg2 (p = 0.01), and in ring3 from 3.1 to 5.7 nv/deg2 (p = 0.02). P1 implicit times improved in ring1 from 44.2 to 32.4 ms (p = 0.01), in ring2 from 45.2 to 33.2 ms (p = 0.02), and in ring3 from 41.9 to 32.4 ms (p = 0.01). The mean amplitude improved in 16 Tds from 2.4 to 5.0 nv/deg2 (p = 0.01) and in 32 Tds from 2.4 to 4.8 nv/deg2 (p = 0.01) in the full-field flicker electroretinography results. Full field flicker electroretinography mean implicit time also improved in 16 Tds from 43.3 to 37.9 ms (p = 0.01). No ocular or systemic adverse events related to the two types of surgical methods and/or Wharton's jelly derived mesenchymal stem cells itself were observed during the follow-up period.

CONCLUSION

RP is a genetic disorder that can result in blindness with outer retinal degeneration. Regardless of the type of genetic mutation, sub-tenon Wharton's jelly derived mesenchymal stem cell administration appears to be an effective and safe option. There are no serious adverse events or ophthalmic / systemic side effects for 6 months follow-up. Although the long-term adverse effects are still unknown, as an extraocular approach, subtenon implantation of the stem cells seems to be a reasonable way to avoid the devastating side effects of intravitreal/submacular injection. Further studies that include long-term follow-up are needed to determine the duration of efficacy and the frequency of application.

TRIAL REGISTRATION

SHGM56733164. Redistered 28 January 2019 https://shgm.saglik.gov.tr/organ-ve-doku-nakli-koordinatorlugu/56733164/203 E.507.

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.

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.

Objective Measurement of Local Rod and Cone Function Using Gaze-Controlled Chromatic Pupil Campimetry in Healthy Subjects

Purpose

We introduce a new approach for functional mapping of rod and cone activity by measuring pupillary responses to local stimulation via gaze-controlled chromatic pupil campimetry (CPC).

Methods

Pupillary constriction amplitude and latency to constriction onset to local photopic and scotopic light stimuli at different locations within the 30° central visual field were analyzed in 14 healthy subjects (4 males, 34 ± 11 years, mean ± standard deviation [SD]). All subjects were measured twice for evaluating the test–retest variability and reproducibility of the method.

Results

For the cone-favoring protocol (ConeProt), the relative maximal constriction amplitude was most pronounced in the center (26.8% ± 6.3%) with a hill-shaped decrease from the fovea to the periphery. For the rod-favoring protocol (RodProt), it was smaller (center, 13.5% ± 4.5%) with a profile lacking the central peak. Mean latency to constriction onset was faster for cones (277 ± 25 ms) than for rods (372 ± 13 ms). Mean intraclass correlation at the different stimulus locations was 0.84 ± 0.08 for RodProt and 0.75 ± 0.11 for ConeProt; mean coefficients of repeatability value of all stimulus locations was 5.9% ± 1.2% and 8.6% ± 1.7%, respectively.

Conclusions

CPC provides an objective evaluation of local rod and cone function within the central 30° visual field. It shows a photoreceptor-specific profile in healthy subjects. Due to its easy, noncontact, gaze-controlled character, it is a clinically applicable method and may fill the gap of functional diagnostics of rods and cones of the human retina.

Translational Relevance

Chromatic pupil campimetry provides information about the local rod and cone function of the human retina with distinct pattern of distributions in an objective manner.

Central mfERG amplitude ratio as a predictor for visual outcome of macular hole surgery

PURPOSE

To investigate whether visual acuity improvement achieved after surgical treatment for macular hole (MH) can be predicted by preoperative multifocal ERG (mfERG) central/peripheral amplitude ratio.

METHODS

Thirty patients with unilateral MH were included. Evaluations with comprehensive ophthalmological examination including best-corrected visual acuity (BCVA) were performed at baseline and 1, 3, 8, 24 and 48 weeks after surgery, while mfERG (Diagnosys LLC; 61 hexagons-30°) and spectral-domain optic coherence tomography (sOCT-Heidelberg Engineering) were performed at baseline and 2 months after surgery. mfERG results are shown by means of the ratio between the amplitudes' average from rings 1 and 2 (central) and rings 4 and 5 (peripheral): the P1 ratio. mfERG data from 20 normally sighted age-matched subjects was used for comparison. A macular hole index (MH index) was defined as the quotient between hole height and base measured on OCT.

RESULTS

Twenty-six patients finished the 48-week follow-up. Mean ± SE (logMAR) preoperative BCVA was 0.93 ± 0.22 and improved in 0.25 ± 0.07 at 48 weeks. mfERG P1 ratio was reduced at baseline and increased significantly after surgery. A significant correlation was observed between preoperative P1 ratio and BCVA gain at week 8 (r = -0.42; P = 0.033). There was no significant correlation between preoperative MH index and postoperative BCVA (P > 0.05).

CONCLUSION

Retinal function assessed using the ratio between central and peripheral mfERG responses might be used as predictor of visual acuity outcome after macular surgery for MH.

Multifocal electroretinogram findings in sickle cell maculopathy

BACKGROUND

The aim of the present work was to describe and compare multifocal electroretinogram findings (mfERG) between patients with sickle cell disease (SCD) without clinical sign of maculopathy and controls (HbAA).

METHODS

Both HbSS (homozygous SCD) and HbSC (compound heterozygous SCD) patients, the two most frequent SCD genotypes, were included. All individuals underwent a full ophthalmologic examination (with a fundoscopy), a spectral domain ocular coherence tomography (SD-OCT) and a mfERG.

RESULTS

A total of 86 subjects were included: 54 SCD patients (107 eyes) with 32 HbSS (63 eyes) and 22 HbSC (44 eyes) and 32 controls (64 eyes). None of the eyes showed retinal clinical abnormalities. SD-OCT analysis showed that macular thickness was statistically lower in SCD eyes than in controls. mfERG analysis demonstrated a significant reduction of N1 (initial-negative deflection), and P1 (positive peak) response amplitude densities of HbSS eyes compared to HbAA eyes from the centre (<2°) and to the periphery (>15°). Implicit time response was also reduced in the centre (<2°). N1 and P1 response amplitude densities of HbSC eyes were significantly lower than those of HbAA eyes from the centre (<2°) to the periphery (>15°). N1 implicit time was statistically reduced in HbSS compared to HbSC eyes.

CONCLUSION

Our study is the first one to describe macular electrophysiological dysfunction in SCD patients. Moreover, we confirm that SCD maculopathy is equally frequent in HbSS and HbSC.

Multifocal Electroretinography in Assessment of Macular Function after Internal Limiting Membrane Peeling in Macular Hole Surgery

Purpose

Internal limiting membrane (ILM) peeling is important for macular hole (MH) surgery but may have secondary effects visible on spectral domain optical coherence tomography (OCT) and multifocal electroretinography (mfERG). We relate integrity of inner and outer macular layers with functional results with mfERG.

Methods

Nonrandomized prospective study of 33 consecutive eyes of 33 patients with macular hole who underwent vitrectomy with ILM peeling. Best-corrected visual acuity was assessed, and integrity of external layers was measured using OCT. Each component of mfERG, N1 and P1 amplitude and latency, was also measured.

Results

All eyes showed macular hole closure. Visual acuity improved from 20/400 to 20/40 in the Snellen visual acuity chart (P < 0.001), and OCT external lines were intact in 19 eyes and disrupted in 14 eyes. Postoperatively, N1 and P1 amplitudes in ring 1 increased compared to preoperative values (P < 0.001 for both). Latency remained delayed for both N1 and P1 wave. In the group of 19 eyes with integrity of outer retinal layers, N1 amplitude in ring 1 was superior to the group of 14 patients with disrupted outer retinal layers (P=0.042).

Conclusions

In macular hole surgery, structure analysis in OCT is one of the important outcomes for the retinal surgeon. Functional results are parallel with anatomic results, but visual gain is limited. The limited recovery in mfERG suggests an alteration of retinal physiology that could explain limited vision recover.

Revealing a retinal facilitatory effect with the multifocal ERG

PURPOSE

We have previously shown that the amplitude of the mfERG response obtained to a single (large) hexagon is significantly smaller than that obtained when summating all the mfERG responses evoked to an array of 7-61 hexagons covering the same retinal area. The purpose of this study was to confirm our initial findings in normal subjects of different ages and in selected patients.

METHODS

Binocular mfERGs (1, 7, 19, 37 and 61 hexagon arrays; Espion V6.0.54 Diagnosys LLC) were recorded from 40 normal subjects (25 aged 18-25, and 15 aged 3-12). Individual mfERG waveforms evoked in response to the multi-hexagon arrays (7, 19, 37 and 61) were summated, and the amplitude of the resulting composite mfERG waveform was compared to that measured in the response evoked to the single (large) hexagon stimulus to yield the amplitude ratio (i.e., 7:1 X100, 19:1X100, etc.).

RESULTS

In normal subjects, the 7:1 ratio was 119.5 ± 9.2%, a value that gradually decreased to reach 109.4 ± 20.6% with the 61:1 ratio and a finding that was similar across all ages.

CONCLUSION

The present study indicates a significant enhancement in amplitude of the summed mfERG composite waveform evoked to the 7 hexagon stimulus array (and to a lesser extent to the 19, 37 and 61 stimuli) compared to the 1 hexagon array, possibly mediated through the retinal lateral pathway (horizontal or amacrine cells), a claim that awaits confirmation. Preliminary results obtained from patients treated with Plaquenil suggest that this new method of mfERG analysis might probe a feature of macular function different from that investigated with the more usual method of mfERG ring ratio.

Cellular-scale evaluation of induced photoreceptor degeneration in the living primate eye

Progress is needed in developing animal models of photoreceptor degeneration and evaluating such models with longitudinal, noninvasive techniques. We employ confocal scanning laser ophthalmoscopy, optical coherence tomography (OCT) and high-resolution retinal imaging to noninvasively observe the retina of non-human primates with induced photoreceptor degeneration. Photoreceptors were imaged at the single-cell scale in three modalities of adaptive optics scanning light ophthalmoscopy: traditional confocal reflectance, indicative of waveguiding; a non-confocal offset aperture technique visualizing scattered light; and two-photon excited fluorescence, the time-varying signal of which, at 730 nm excitation, is representative of visual cycle function. Assessment of photoreceptor structure and function using these imaging modalities revealed a reduction in retinoid production in cone photoreceptor outer segments while inner segments appeared to remain present. Histology of one retina confirmed loss of outer segments and the presence of intact inner segments. This unique combination of imaging modalities can provide essential, clinically-relevant information on both the structural integrity and function of photoreceptors to not only validate models of photoreceptor degeneration but potentially evaluate the efficacy of future cell and gene-based therapies for vision restoration.

Neuropeptide Y treatment induces retinal vasoconstriction and causes functional and histological retinal damage in a porcine ischaemia model

PURPOSE

To investigate the effects of intravitreal neuropeptide Y (NPY) treatment following acute retinal ischaemia in an in vivo porcine model. In addition, we evaluated the vasoconstrictive potential of NPY on porcine retinal arteries ex vivo.

METHODS

Twelve pigs underwent induced retinal ischaemia by elevated intraocular pressure clamping the ocular perfusion pressure at 5 mmHg for 2 hr followed by intravitreal injection of NPY or vehicle. After 4 weeks, retinas were evaluated functionally by standard and global-flash multifocal electroretinogram (mfERG) and histologically by thickness of retinal layers and number of ganglion cells. Additionally, the vasoconstrictive effects of NPY and its involved receptors were tested using wire myographs and NPY receptor antagonists on porcine retinal arteries.

RESULTS

Intravitreal injection of NPY after induced ischaemia caused a significant reduction in the mean induced component (IC) amplitude ratio (treated/normal eye) compared to vehicle-treated eyes. This reduction was accompanied by histological damage, where NPY treatment reduced the mean thickness of inner retinal layers and number of ganglion cells. In retinal arteries, NPY-induced vasoconstriction to a plateau of approximately 65% of potassium-induced constriction. This effect appeared to be mediated via Y1 and Y2, but not Y5.

CONCLUSION

In seeming contrast to previous in vitro studies, intravitreal NPY treatment caused functional and histological damage compared to vehicle after a retinal ischaemic insult. Furthermore, we showed for the first time that NPY induces Y1- and Y2- but not Y5-mediated vasoconstriction in retinal arteries. This constriction could explain the worsening in vivo effect induced by NPY treatment following an ischaemic insult and suggests that future studies on exploring the neuroprotective effects of NPY might focus on other receptors than Y1 and Y2.

Early and localized retinal dysfunction in patients with type 1 diabetes mellitus studied by multifocal electroretinogram

AIMS

To investigate the function of localized retinal areas in highly selected type 1 diabetes mellitus patients (DM1) with no or mild signs of diabetic retinopathy (NO DR and NPDR, respectively) and its correlation with age, diabetes duration and glycemic control.

METHODS

Multifocal electroretinograms (mfERG) were recorded in 35 eyes of 18 NO DR patients and 38 eyes of 19 NPDR patients. Thirty-one eyes of 17 normal subjects were enrolled as controls. N1-P1 response amplitude densities (RADs) and P1 implicit times (ITs) from isolated (R1: 0°-2.5°, R2: 2.5°-5°, R3: 5°-10°) and combined (R1 + R2, R2 + R3 and R1 + R2 + R3) annular rings and from four retinal sectors (nasal, N; temporal, T; superior, S and inferior, I) with increasing eccentricities up to 10° (S1, S2, S3, S1 + S2, S1 + S2 + S3) were measured. The statistical differences between DM1 groups and controls were tested by ANOVA. The electrophysiological data were correlated with age, duration of diabetes and glycated hemoglobin (HbA1c) level using the Pearson's test.

RESULTS

MfERG RADs, but not ITs, from all isolated and combined rings and sectors up to 10° of foveal eccentricity were statistically different between DM1 groups compared to controls. No significant differences were found between NO DR and NPDR patients. The mfERG abnormalities of the central retinal areas were correlated significantly with age in both DM1 groups and with diabetes duration mainly in NPDR group.

CONCLUSIONS

In DM1 patients, localized retinal dysfunction, described by reduced mfERG RAD, can be observed also in the absence of clinical signs of DR and it is related to aging.

Soft transparent graphene contact lens electrodes for conformal full-cornea recording of electroretinogram

Visual electrophysiology measurements are important for ophthalmic diagnostic testing. Electrodes with combined optical transparency and softness are highly desirable, and sometimes indispensable for many ocular electrophysiology measurements. Here we report the fabrication of soft graphene contact lens electrodes (GRACEs) with broad-spectrum optical transparency, and their application in conformal, full-cornea recording of electroretinography (ERG) from cynomolgus monkeys. The GRACEs give higher signal amplitude than conventional ERG electrodes in recordings of various full-field ERG responses. High-quality topographic mapping of multifocal ERG under simultaneous fundus monitoring is realized. A conformal and tight interface between the GRACEs and cornea is revealed. Neither corneal irritation nor abnormal behavior of the animals is observed after ERG measurements with GRACEs. Furthermore, spatially resolved ERG recordings on rabbits with graphene multi-electrode array reveal a stronger signal at the central cornea than the periphery. These results demonstrate the unique capabilities of the graphene-based electrodes for in vivo visual electrophysiology studies.

Effects of subtenon-injected autologous platelet-rich plasma on visual functions in eyes with retinitis pigmentosa: preliminary clinical results

PURPOSE

One of the main reasons for apoptosis and dormant cell phases in degenerative retinal diseases such as retinitis pigmentosa (RP) is growth factor withdrawal in the cellular microenvironment. Growth factors and neurotrophins can significantly slow down retinal degeneration and cell death in animal models. One possible source of autologous growth factors is platelet-rich plasma. The purpose of this study was to determine if subtenon injections of autologous platelet-rich plasma (aPRP) can have beneficial effects on visual function in RP patients by reactivating dormant photoreceptors.

MATERIAL AND METHODS

This prospective open-label clinical trial, conducted between September 2016 and February 2017, involved 71 eyes belonging to 48 RP patients with various degrees of narrowed visual field. Forty-nine eyes belonging to 37 patients were injected with aPRP. A comparison group was made up of 11 patients who had symmetrical bilateral narrowed visual field (VF) of both eyes. Among these 11 patients, one eye was injected with aPRP, while the other eye was injected with autologous platelet-poor plasma (aPPP) to serve as a control. The total duration of the study was 9 weeks: the aPRP or aPPP subtenon injections were applied three times, with 3-week intervals between injections, and the patients were followed for three more weeks after the third injection. Visual acuity (VA) tests were conducted on all patients, and VF, microperimetry (MP), and multifocal electroretinography (mfERG) tests were conducted on suitable patients to evaluate the visual function changes before and after the aPRP or aPPP injections.

RESULTS

The best-corrected visual acuity values in the ETDRS chart improved by 11.6 letters (from 70 to 81.6 letters) in 19 of 48 eyes following aPRP application; this result, however, was not statistically significant (p = 0.056). Following aPRP injections in 48 eyes, the mean deviation of the VF values improved from - 25.3 to - 23.1 dB (p = 0.0001). Results regarding the mfERG P1 amplitudes improved in ring 1 from 24.4 to 38.5 nv/deg² (p = 0.0001), in ring 2 from 6.7 to 9.3 nv/deg² (p = 0.0301), and in ring 3 from 3.5 to 4.5 nv/deg² (p = 0.0329). The mfERG P1 implicit times improved in ring 1 from 40.0 to 34.4 ms (p = 0.01), in ring 2 from 42.5 to 33.2 ms (p = 0.01), and in ring 3 from 42.1 to 37.9 ms (p = 0.04). The mfERG N1 amplitudes improved in ring 1 from 0.18 to 0.25 nv/deg² (p = 0.011) and in ring 2 from 0.05 to 0.08 nv/deg² (p = 0.014). The mfERG N1 implicit time also improved in ring 1 from 18.9 to 16.2 ms (p = 0.040) and in ring 2 from 20.9 to 15.5 ms (p = 0.002). No improvement was seen in the 11 control eyes into which aPPP was injected. In the 23 RP patients with macular involvement, the MP average threshold values improved with aPRP injections from 15.0 to 16.4 dB (p = 0.0001). No ocular or systemic adverse events related to the injections or aPRP were observed during the follow-up period.

CONCLUSION

Preliminary clinical results are encouraging in terms of statistically significant improvements in VF, mfERG values, and MP. The subtenon injection of aPRP seems to be a therapeutic option for treatment and might lead to positive results in the vision of RP patients. Long-term results regarding adverse events are unknown. There have not been any serious adverse events and any ophthalmic or systemic side effects for 1 year follow-up. Further studies with long-term follow-up are needed to determine the duration of efficacy and the frequency of application.

Combination of Multifocal Electroretinogram and Spectral-Domain OCT Can Increase Diagnostic Efficacy of Parkinson's Disease

Background

The retinal changes have been identified in morphology and function in Parkinson's disease (PD). However, the controversial results suggest that it is incredible that only using a single method for testing retinal change to evaluate Parkinson's disease. The aim of this study was to assess retinal changes and increase the diagnostic efficacy of Parkinson's disease with a combination of multifocal electroretinogram (mf-ERG) and spectral domain optical coherence tomography (SD-OCT) examinations.

Method

Fifty-three PD patients and forty-one healthy controls were enrolled. Subjects were assessed for retinal function using mf-ERG and retinal structure using SD-OCT.

Results

The PD patients had a significantly decreased amplitude density of P1 and a delayed implicit time of P1 in some regions. The macular retinal thickness, macular volume, and average RNFL thickness were decreased in PD. The AUC of a single parameter of either retinal function or structure was low. Both of them were higher in diagnostic value to discriminate PD patients.

Conclusion

The amplitude density of P1 combined with macular volume can get a high diagnostic efficacy to discriminate between participants with or without PD. It indicates that a combination of mf-ERG and SD-OCT provides a good clinical biomarker for diagnosis of PD.

Retinal dysfunction characterizes subtypes of dominant optic atrophy

PURPOSE

To assess preganglionic retinal function using multifocal electroretinogram (mfERG) in patients affected by dominant optic atrophy (DOA) stratified by OPA1 gene mutation.

METHODS

Multifocal electroretinogram (mfERG) was recorded in 18 DOA patients (DOA group, 35 eyes) and 25 age-matched healthy subjects (control group, 25 eyes). Patients were stratified in two groups based on gene mutation: missense mutation (DOA-M group, 11 eyes) and mutation causing haploinsufficiency (DOA-H group, 24 eyes). The mfERG N1-P1 response amplitude density (RAD) has been evaluated in five annular retinal areas with different eccentricity from the fovea (ring 1: 0-5 degrees, R1; ring 2: 5-10 degrees, R2; ring 3: 10-15 degrees, R3; ring 4: 15-20 degrees, R4; and ring 5: 20-25 degrees, R5) and in eight sectors on the basis of the retinal topography: temporal-superior (TS), temporal-inferior (TI), nasal-superior (NS) and nasal-inferior (NI), temporal (T), superior (S), nasal (N) and inferior (I).

RESULTS

Compared to controls, DOA group revealed a significant reduction in N1-P1 RADs values in R1-R4 rings and in TI, NS and N sectors [analysis of variance (ANOVA), p < 0.01). DOA-M group showed a significant reduction in N1-P1 RADs values in R1-R5 rings and in TI, NS, NI, T, N and I sectors (p < 0.01). Dominant optic atrophy-H (DOA-H) group displayed only a significant (p < 0.01) reduction in N1-P1 RADs values, exclusively in R1 and in the NS sector.

CONCLUSION

Preganglionic retinal impairment occurs in DOA with a clear genotype to retinal dysfunction association. Missense mutations are characterized by a far more severe functional impairment.

Association between Early Neuroretinal Dysfunction and Peripheral Motor Unit Loss in Patients with Type 1 Diabetes Mellitus

OBJECTIVES

It has been already confirmed that retinal neurodegeneration has a predictive value in the development of microvascular alterations in diabetic retinopathy. However, no data are available on the association between neuroretinal dysfunction and peripheral motor unit loss. Our study, therefore, was aimed at investigating the hypothesis that retinal neurodegeneration could be considered an early marker of diabetic peripheral neuropathy (DPN).

METHODS

20 T1DM patients with no symptoms/signs of peripheral polyneuropathy, without DR or with very mild nonproliferative DR, and 14 healthy controls (C) age- and gender-matched were enrolled. The following electrophysiological tests were performed: standard nerve conduction studies (NCS) and incremental motor unit number estimation (MUNE) from the abductor hallux (AH) and abductor digiti minimi (ADM). Neuroretinal function was studied by multifocal electroretinogram (MfERG) recordings, measuring response amplitude density (RAD) and implicit time (IT) from rings and sectors of superior (S)/inferior (I)/temporal (T)/nasal (N) macular sectors up to 10 degrees of foveal eccentricity.

RESULTS

MfERG RADs from rings and sectors were significantly reduced in T1DM (p < 0.05) vs. C. ADM MUNE and AH MUNE were significantly decreased in T1DM (p = 0.039 and p < 0.0001, respectively) vs. C. A positive correlation between mean MfERG RADs from the central 5 degrees of the four (S, I, T, and N) macular sectors and lower limb motor unit number (r = 0.50, p = 0.041; r = 0.64, p = 0.005; r = 0.64, p = 0.006; and r = 0.61, p = 0.010, respectively) was observed in T1DM patients. No abnormalities of NCS were found in any subject.

CONCLUSIONS

The motor unit loss on the one hand and neuroretinal dysfunction on the other hand are already present in T1DM patients without DPN. The relationship between neuroretinal dysfunction and motor unit decline supports the hypothesis that neuroretina may represent a potential "window" to track the early neurogenic damage in diabetes.

Multifocal electroretinography changes at the 1-year follow-up in a cohort of diabetic macular edema patients treated with ranibizumab

PURPOSE

To determine the changes in the multifocal electroretinogram (mfERG) at 1 year in a clinical series of diabetic macular edema (DME) patients treated with ranibizumab (RNBZ) using a pro re nata protocol.

METHODS

We analyzed a clinical series of 35 eyes of 35 patients with DME at baseline and after treating them with RNBZ over 1 year, in order to determine the change in the macular function, which was assessed by means of the response density and the implicit time of the first-order kernel (FOK) P1 wave of the mfERG at the foveola (R1), fovea (R2) and parafovea (R3). These electrophysiological parameters were studied taking into account different independent variables, such as DME type, degree of diabetic retinopathy (DR), level of preservation of both the ellipsoid zone (IS/OS) and the external limiting membrane (ELM) and changes in central retinal thickness (CRT) and total macular volume (TMV). We also studied the relationship between the response density and the best-corrected visual acuity (BCVA).

RESULTS

Eyes with cystic and spongiform DME showed better response density with respect to the serous type (p < 0.001) at baseline. Similarly, eyes with high IS/OS and ELM preservation rates showed higher initial response density compared to the others (p < 0.001). Eyes with moderate DR had better response density compared to those with severe and proliferative DR (p = 0.001). At the beginning of the study, those eyes with proliferative and severe DR showed longer implicit times with respect to those with moderate DR (p = 0.04). The response density significantly increased in eyes that anatomically restored the IS/OS and the ELM after being treated with RNBZ (both p < 0.001). Similarly, eyes with spongiform DME further improved the response density with respect to those with cystic and serous DME (p < 0.001). On the contrary, eyes with hard exudates showed less improvement in their response density at the end of the study (p < 0.001). We observed a significant relationship between BCVA and the response density achieved at the end of the study (p = 0.012). Eyes with severe and proliferative DR significantly shortened implicit time compared to those with moderate DR (p = 0.04).

CONCLUSIONS

The multifocal electroretinogram allowed us to differentiate groups of eyes with DME according to their electrophysiological profile, both initially and after being treated with RNBZ. Ranibizumab increased the response density in all DME types included in the study, with a maximum response in those eyes with spongiform type. Once treated with RNBZ, the macular electrophysiological activity improved in eyes that had a well-preserved ellipsoid zone and ELM. The presence of hard exudates was a limitation to the response density achieved at the foveola.

Structural and functional assessment after intravitreal injection of ranibizumab in diabetic macular edema

PURPOSE

To evaluate structure and function improvement in central retina by optical coherence tomography (OCT) and multifocal electroretinography (mf-ERG) in diabetic macular edema (DME) patients after intravitreal injection of ranibizumab (IVR) treatment.

METHODS

Twenty-seven eyes in 27 patients with DME received three consecutive monthly injections of IVR (0.05 ml, 10 mg/ml) and as needed thereafter. The clinical parameters of best-corrected visual acuity (BCVA), central foveal thickness (CFT) and mf-ERG were monitored for 6 months before and after IVR. The findings at baseline, 1, 3 and 6 months were analyzed. Correlation and regression analyses were performed on BCVA, CFT, mf-ERG amplitude and implicit time of the N1 and P1 waves.

RESULTS

IVR significantly improved visual acuity from the beginning of the treatment (P < 0.05). There were significant decreases in the CFT compared with the baseline after IVR (P < 0.05). The mean amplitude of P1 and N1 in the central ring at all examinations increased significantly compared with the baseline (P < 0.05). The mean P1 and N1 implicit times in the central ring were shortened, but not significantly (P > 0.05). There were significant correlations of BCVA with CFT, P1 and N1 amplitudes in the central retina (P < 0.05).

CONCLUSION

In addition to the improvement in BCVA and the reduction in CFT, IVR improved macular retinal function, as assessed by mf-ERG, in diabetic eyes. The combination of OCT and mf-ERG for macular evaluation may better assess DME.

Cellular origin of intrinsic optical signals in the rabbit retina

Optical imaging of retinal intrinsic signals is a relatively new method that provides spatiotemporal patterns of retinal activity through activity-dependent changes in light reflectance of the retina. The exact physiological mechanisms at the origin of retinal intrinsic signals are poorly understood and there are significant inter-species differences in their characteristics and cellular origins. In this study, we re-examined this issue through pharmacological dissection of retinal intrinsic signals in the rabbit with simultaneous ERG recordings. Retinal intrinsic signals faithfully reflected retinal activity as their amplitude was strongly associated with stimulation intensity (r²=0.85). Further, a strong linear relation was found using linear regression (r²=0.98) between retinal intrinsic signal amplitude and the ERG b wave, which suggests common cellular origins. Intravitreal injections of pharmacological agents were performed to isolate the activity of the retina's major cell types. Retinal intrinsic signals were abolished when the photoreceptors' activity was isolated with aspartate, indicative that they are not at the origin of this signal. A small but significant decrease in intrinsic response (20%) was observed when ganglion and amacrine cells' activity was inhibited by TTX injections. The remaining intrinsic responses were abolished in a dose-dependent manner through the inhibition of ON-bipolar cells by APB. Our results indicate that, in rabbits, retinal intrinsic signals reflect stimulation intensity and originate from the inner retina with a major contribution of bipolar cells and a minor one from ganglion or amacrine cells.

The Role of mf-ERG in the Diagnosis and Treatment of Age-Related Macular Degeneration: Electrophysiological Features of AMD

INTRODUCTION

Age-related macular cegeneration (AMD) is the leading cause of visual dysfunction worldwide, affecting 9-25% of individuals between 65 and 75 years old.

METHODS

We have reviewed the published articles investigating the role of multifocal electroretinogram (mf-ERG) in the diagnosis and treatment of AMD.

RESULTS

Visual evoked potentials have revealed decreased amplitudes and higher latencies in patients with AMD, while the degeneration of photoreceptors and abnormalities of retinal pigment epithelium can be identified by electro-oculogram recordings. Moreover, ERG can detect the functional abnormalities observed in AMD and evaluate each therapeutic approach. The record of local electrophysiological responses coming from different retinal areas can be accurately performed by mfERG.

CONCLUSION

The accuracy of mfERG in detecting the degeneration of photoreceptors, as well the disturbances of macular function, could be useful both in the early diagnosis of AMD and the assessment of treatment efficacy.

A late foveal response component of multifocal electroretinograms in healthy subjects

PURPOSE

To investigate the characteristics of the late foveal response component (lfrc) that presents on the first slice of the second-order kernel (K2.1) in multifocal electroretinograms (mfERGs).

METHODS

mfERGs with 37 hexagonal stimulus elements were obtained from 27 healthy subjects under a stimulus intensity of 2.67 cds/m², base rate of 75 Hz, and a net recording time of 1 min 49.2 s, using bipolar contact lens electrodes. The responses on the centermost hexagon (with a diameter of 4.5°-5.2°) were designated as foveal mfERGs.

RESULTS

The foveal mfERG of the first-order kernel (K1) was shaped similarly to the K1 of the surrounding mfERGs. The foveal mfERG of K2.1 differed from the K2.1s of the surrounding mfERGs. This difference varied among subjects; however, the potential (0.34 ± 0.10 µV: mean ± SD) of the lfrc acutely changed at approximately 50 ms (range 48.56 ± 1.02-56.86 ± 1.99 ms). Whereas the amplitudes of the other major components of K1 and K2.1 significantly decreased with increasing refractive error, the amplitude of lfrc was not significantly correlated with refraction in this cohort.

CONCLUSIONS

The lfrc was obtained only on the centermost hexagon within an appropriate recording time (<2 min). This finding reflects the particular structure and peculiar adaptiveness of the fovea, a specialized area of the human retina, and enables the estimation of foveal function in clinical practice.

Fixation stability and implication for multifocal electroretinography in patients with neovascular age-related macular degeneration after anti-VEGF treatment

PURPOSE

To quantify fixation stability in patients with neovascular age-related macular degeneration (nAMD) at baseline, 3 and 6 months after anti-vascular endothelial growth factor (anti-VEGF) treatment and furthermore asses the implications of an unsteady fixation for multifocal electroretinography (mfERG) measurements.

METHODS

Fifty eyes of 50 nAMD patients receiving intravitreal anti-VEGF treatment with either bevacizumab or ranibizumab and eight eyes of eight control subjects were included. Fixation stability measurements were performed with the Eye-Link eyetracking system and the retinal area in degrees² (deg²) containing the 68 % most frequently used fixation points (RAF68) was calculated. MfERG P1 amplitude and implicit time were analyzed in six concentric rings and as a summed response. Patients were examined at baseline, 3 and 6 months. Four different mfERG recordings were performed for the control subjects to mimic an involuntary unstable fixation: normal central fixation, 2.4°, 4.8°, and 7.1° fixation instability.

RESULTS

For control subjects, a fixation instability of 2.4° (corresponding to the central hexagon) did not reduce mfERG ring amplitudes significantly, whereas 4.8° and 7.1° fixation instability reduced the amplitudes significantly in rings 1 and 2 (p < 0.001) as well as in the peripheral rings in the 7.1° instability condition (p < 0.001). Fixation stability improved non-significantly for patients at 3 and 6 months. The size of the retinal area of fixation was at baseline, 3 and 6 months negatively correlated to visual acuity (VA) (r_baseline = -0.65, r_{3 months} = -0.60, and r_{6 months} = -0.66 respectively, p < 0.001) and mfERG amplitudes of the three innermost rings (r_baseline = -0.29, p = 0.042, r_3 months = -0.43, p = 0.003 and r_6 months = -0.31, p = 0.042). The VA cutoff for a fixation area less than 5 deg² (approximately the central hexagon) was 65, 77, and 68 ETDRS letters (corresponding a maximal Snellen equivalent of 0.31) at baseline, 3 and 6 months, respectively.

CONCLUSIONS

MfERG amplitudes in recordings of nAMD patients are at substantial risk of being reduced due to poor fixation as a large number of patients may use a fixation area of more than 5 deg². Fixation monitoring during recording as well as interpretation of results should be performed with care, especially in patients with poor visual acuity.

The effect of nutritional supplementation on the multifocal electroretinogram in healthy eyes

BACKGROUND

Previous studies have demonstrated an increase in macular pigment optical density (MPOD) with lutein (L)-based supplementation in healthy eyes. However, not all studies have assessed whether this increase in MPOD is associated with changes to other measures of retinal function such as the multifocal ERG (mfERG). Some studies also fail to report dietary levels of L and zeaxanthin (Z). Because of the associations between increased levels of L and Z, and reduced risk of AMD, this study was designed to assess the effects of L-based supplementation on mfERG amplitudes and latencies in healthy eyes.

METHODS

Multifocal ERG amplitudes, visual acuity, contrast sensitivity, MPOD and dietary levels of L and Z were assessed in this longitudinal, randomized clinical trial. Fifty-two healthy eyes from 52 participants were randomly allocated to receive a L-based supplement (treated group), or no supplement (non-treated group).

RESULTS

There were 25 subjects aged 18-77 (mean age ± SD; 48 ± 17) in the treated group and 27 subjects aged 21-69 (mean age ± SD; 43 ± 16) in the non-treated group. All participants attended for three visits: visit one at baseline, visit two at 20 weeks and visit three at 40 weeks. A statistically significant increase in MPOD (F = 17.0, p ≤ 0.001) and shortening of mfERG ring 2 P1 latency (F = 3.69, p = 0.04) was seen in the treated group.

CONCLUSIONS

Although the results were not clinically significant, the reported trend for improvement in MPOD and mfERG outcomes warrants further investigation.

The effects of fundus photography on the multifocal electroretinogram

PURPOSE

To determine the effect of flash fundus photography (FFP) on the multifocal electroretinogram (mfERG).

METHODS

Ten subjects underwent mfERG testing on three separate dates. Subjects received either mfERG without FFP, mfERG at 5 and 15 min after FFP, or mfERG at 30 and 45 min after FFP on each date. The FFP groups received 10 fundus photographs followed by mfERG testing, first of the right eye then of the left eye 10 min later. Data were averaged and analyzed in six concentric rings at each time point. Average amplitude and implicit times of the N1, P1, and N2 peaks for each concentric ring at each time point after FFP were compared to baseline.

RESULTS

Flash fundus photography did not lead to a significant change of amplitude or implicit times of N1, P1, or N2 at 5 min after light exposure.

CONCLUSIONS

These findings suggest that it is acceptable to perform mfERG testing without delay after performance of FFP.