The clinical applications of multifocal electroretinography: a systematic review

Multifocal Electroretinography Changes after UBX1325 (Foselutoclax) Treatment in Neovascular Age-Related Macular Degeneration

Background/Objectives: The objective of this study was to determine the treatment effect of foselutoclax in neovascular age-related macular degeneration (AMD) by multifocal electroretinography (mfERG) and evaluate mfERG as a potential clinical endpoint in AMD studies. Methods: A total of five subjects were included in the study who had active choroidal neovascularization and a history of at least two anti-vascular endothelial growth factor (VEGF) injections in the last 6 months. Subjects received a 50 µL intravitreal injection of foselutoclax at the baseline visit and Weeks 4, 24, and 28 of the study period. Results: After foselutoclax treatment, the largest improvement in the mfERG N1-P1 response density occurred at Week 8 as three of five subjects achieved a ≥20% gain. In addition, three of five subjects demonstrated a BCVA improvement of ≥5 ETDRS letters over baseline at Weeks 4, 8, and 24. The mean change in BCVA demonstrated statistical significance in Weeks 4 and 8, showing increases of 5 (p = 0.02) and 6.2 (p = 0.02) letters, respectively. Conclusions: Foselutoclax treatment was shown to have the potential to recover outer retinal function as determined by mfERG and BCVA at approximately Week 8 of treatment.

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.

A simplification of intricate multifocal electroretinogram understanding: A mini-review

Variation of multifocal electroretinogram (mfERG) data presentation in existing scientific publications is a challenge for eye care practitioners to apply the scientific information for evidence-based practice in patient management. This review offers an overview of the mfERG data presentation types. Eight types of data presentation in the form of a table, scatter plot, line graph, bar graph/box plot, single waveform/a group of waveforms, trace array topography, three-dimensional topography, and two-dimensional topography are identified. The table format is used to provide the exact values. Line graphs, scatter, and box plots offer information about the relationship of mfERG values. Waveforms are helpful for comparison between groups or conditions. Topographies outline the retinal, especially the specific localized retinal abnormalities. An infographic of fundamental mfERG electrical response with definitions and clinical indications is provided to bridge the gap between researchers and clinicians to facilitate efficient clinical application.

[Multimodal topographically oriented approach to the study of full-thickness macular holes]

PURPOSE

This article studies the relationship between structural changes according to the findings of optical coherence tomography (OCT) and OCT angiography (OCTA), microperimetry (MP), multifocal electroretinography (mfERG) parameters in topographically corresponding areas of the macular region in idiopathic full-thickness macular holes (FTMH).

MATERIAL AND METHODS

OCT, OCTA, MP and mfERG were performed in 14 eyes with FTMH stages I-IV according to Gass. In 13 points at a distance of 0-2.5°, 2.5-5.0°, and 5.0-10.0° from the fixation point, the light sensitivity (LS), amplitude and latency of the P1 component were compared with the size of the hole, the area of cystic changes (CC) at the level of the inner nuclear layer (INL) and the outer plexiform layer and Henle fiber layer complex (OPL+HFL), vessel density in the superficial and deep capillary plexus (SCP and DCP).

RESULTS

LS and P1 component amplitude were significantly reduced at a distance of up to 5.0° from the fixation point. LS correlates with the apical and basal diameter of the hole (R> -0.53), the area of CC in the INL (R> -0.62) and the OPL+HFL complex (R> -0.55), the density of vessels in the SCP at a distance of up to 2.5° from the fixation point (R>0.51) and in the DCP at a distance of up to 5° from the fixation point (R>0.49). The P1 amplitude correlates with the basal diameter of the hole (R= -0.38), the area of CC in the INL and the OPL+HFL complex (R> -0.33) and vessel density in the SCP (R=0.37) at a distance of up to 2.5° from the fixation point, as well as vessel density in the DCP at a distance of up to 5° from the fixation point (R=0.47). Vessel density in the DCP is significantly lower in the presence of CC in the retina (p<0.001).

CONCLUSION

In FTMH, there is a relationship between bioelectrical activity and LS, and structural disorders, capillary perfusion in different layers of the retina. A multimodal topographically oriented approach allows studying the relationship between structural and functional parameters in individual points of the retina and can be used in monitoring of FTMH after surgical treatment.

Multifocal Electroretinography Changes over 12 Months after Resolution of Central Serous Chorioretinopathy: Prospective Observational Study

INTRODUCTION

This prospective observational study aimed to evaluate the changes in retinal function after the anatomical resolution of central serous chorioretinopathy by multifocal electroretinography.

METHODS

Thirty-two eyes of 32 patients with unilaterally resolved central serous chorioretinopathy were prospectively studied. Serial multifocal electroretinography examinations were performed at the initial visit for active central serous chorioretinopathy, the time of anatomical resolution (resolved central serous chorioretinopathy), and 3, 6, and 12 months after resolution. The peak amplitudes of the first kernel responses were analysed and compared with those in 27 age-matched normal controls.

RESULTS

Compared with controls, the N1 amplitudes of rings 1-4 and P1 amplitudes of rings 1-3 showed statistically significant reductions at 12 months after the resolution of central serous chorioretinopathy (p < 0.05). The multifocal electroretinography amplitude substantially increased at the time of resolution and gradually improved until 3 months after the resolution of central serous chorioretinopathy.

CONCLUSION

Serial examinations with multifocal electroretinography showed that retinal responses increased mostly after the resolution of central serous chorioretinopathy, and this improvement slowly progressed until 3 months; however, the multifocal electroretinography amplitudes remained statistically reduced 12 months after the anatomical resolution of central serous chorioretinopathy, indicating the residual functional deficits detected by multifocal electroretinography.

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.

Diabetes mellitus associated neurovascular lesions in the retina and brain: A review

Diabetes mellitus (DM) is now recognized as a system-wide, autoimmune, inflammatory, microvascular disorder, which, in the retina and brain results in severe multifocal injury now recognized as a leading cause, world-wide, of progressive vision loss and dementia. To address this problem, resulting primarily from variations in glycemia in the prediabetic and overt diabetic states, it must be realized that, although some of the injury processes associated with diabetes may be system wide, there are varying responses, effector, and repair mechanisms that differ from organ to organ or within varying cell structures. Specifically, within the retina, and similarly within the brain cortex, lesions occur of the "neurovascular unit", comprised of focal microvascular occlusions, inflammatory endothelial and pericyte injury, with small vessel leakage resulting in injury to astrocytes, Müller cells, and microglia, all of which occur with progressive neuronal apoptosis. Such lesions are now recognized to occur before the first microaneurysms are visible to imaging by fundus cameras or before they result in detectable symptoms or signs recognizable to the patient or clinician. Treatments, therefore, which currently are not initiated within the retina until edema develops or there is progression of vascular lesions that define the current staging of retinopathy, and in the brain only after severe signs of cognitive failure. Treatments, therefore are applied relatively late with some reduction in progressive cellular injury but with resultant minimal vision or cognitive improvement. This review article will summarize the multiple inflammatory and remediation processes currently understood to occur in patients with diabetes as well as pre-diabetes and summarize as well the current limitations of methods for assessing the structural and functional alterations within the retina and brain. The goal is to attempt to define future screening, monitoring, and treatment directions that hopefully will prevent progressive injury as well as enable improved repair and attendant function.

The Effect of Dietary Supplementations on Delaying the Progression of Age-Related Macular Degeneration: A Systematic Review and Meta-Analysis

Purpose: Age-related macular degeneration (AMD) is a neurodegenerative ophthalmic disease. The purpose of this systematic review (SR) and meta-analysis was to evaluate if dietary supplementation alone or in combinations might delay the progression of any of the stages of AMD. Methods: A SR and meta-analysis identifying cohort studies and randomized controlled trials (RCTs) evaluating the effect of supplements in patients diagnosed with AMD. PubMed, Scopus, Web of Science, CINAHL, and Cochrane were searched through 8th October 2021. Results: Twenty studies, examining 5634 participants ranging from 55 to 80 years, were included in the SR. Eight studies were selected for meta-analysis (414 and 216 subjects in the intervention and control groups). Lutein and zeaxanthin plus n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) supplementation showed significant improvements in best-corrected visual acuity (BCVA) (SMD: -1.99, 95% CI: -3.33, -0.65) compared to the control group. Multifocal electroretinogram results (mfERG) were significantly improved overall (SMD: 4.59, 95% CI: 1.75, 7.43) after lutein plus zeaxanthin supplementation. Conclusions: Combinations of lutein and zeaxanthin with n-3 LC-PUFA might be beneficial in preventing AMD progression and deterioration of visual function. Our results encourage initiating further studies with combinations of n-3 LC-PUFA, lutein, and zeaxanthin especially in early AMD patients.

Electroretinogram responses in myopia: a review

The stretching of a myopic eye is associated with several structural and functional changes in the retina and posterior segment of the eye. Recent research highlights the role of retinal signaling in ocular growth. Evidence from studies conducted on animal models and humans suggests that visual mechanisms regulating refractive development are primarily localized at the retina and that the visual signals from the retinal periphery are also critical for visually guided eye growth. Therefore, it is important to study the structural and functional changes in the retina in relation to refractive errors. This review will specifically focus on electroretinogram (ERG) changes in myopia and their implications in understanding the nature of retinal functioning in myopic eyes. Based on the available literature, we will discuss the fundamentals of retinal neurophysiology in the regulation of vision-dependent ocular growth, findings from various studies that investigated global and localized retinal functions in myopia using various types of ERGs.

From the PnTx2-6 Toxin to the PnPP-19 Engineered Peptide: Therapeutic Potential in Erectile Dysfunction, Nociception, and Glaucoma

The venom of the “armed” spider Phoneutria nigriventer comprises several potent toxins. One of the most toxic components from this venom is the neurotoxin PnTx2-6 (LD50 = ∼ 0.7 μg/mouse, 48 residues, five disulfide bridges, MW = 5,289.31 Da), which slows down the inactivation of various Na+ channels. In mice and rats, this toxin causes priapism, an involuntary and painful erection, similar to what is observed in humans bitten by P. nigriventer. While not completely elucidated, it is clear that PnTx2-6 potentiates erectile function via NO/cGMP signaling, but it has many off-target effects. Seeking to obtain a simpler and less toxic molecule able to retain the pharmacological properties of this toxin, we designed and synthesized the peptide PnPP-19 (19 residues, MW = 2,485.6 Da), representing a discontinuous epitope of PnTx2-6. This synthetic peptide also potentiates erectile function via NO/cGMP, but it does not target Na+ channels, and therefore, it displays nontoxic properties in animals even at high doses. PnPP-19 effectively potentiates erectile function not only after subcutaneous or intravenous administration but also following topical application. Surprisingly, PnPP-19 showed central and peripheral antinociceptive activity involving the opioid and cannabinoid systems, suggesting applicability in nociception. Furthermore, considering that PnPP-19 increases NO availability in the corpus cavernosum, this peptide was also tested in a model of induced intraocular hypertension, characterized by low NO levels, and it showed promising results by decreasing the intraocular pressure which prevents retinal damage. Herein, we discuss how was engineered this smaller active non-toxic peptide with promising results in the treatment of erectile dysfunction, nociception, and glaucoma from the noxious PnTx2-6, as well as the pitfalls of this ongoing journey.

Functional Optical Coherence Tomography for Intrinsic Signal Optoretinography: Recent Developments and Deployment Challenges

Intrinsic optical signal (IOS) imaging of the retina, also termed as optoretinogram or optoretinography (ORG), promises a non-invasive method for the objective assessment of retinal function. By providing the unparalleled capability to differentiate individual retinal layers, functional optical coherence tomography (OCT) has been actively investigated for intrinsic signal ORG measurements. However, clinical deployment of functional OCT for quantitative ORG is still challenging due to the lack of a standardized imaging protocol and the complication of IOS sources and mechanisms. This article aims to summarize recent developments of functional OCT for ORG measurement, OCT intensity- and phase-based IOS processing. Technical challenges and perspectives of quantitative IOS analysis and ORG interpretations are discussed.

Longitudinal multimodal functional macular analysis after half-dose photodynamic therapy for central serous chorioretinopathy

BACKGROUND

Half-dose photodynamic therapy (HD-PDT) has been widely used for central serous chorioretinopathy (CSC) with good anatomical results. However, long-term functional outcomes after this treatment remain uncertain. This study aimed a longitudinal multimodal macular assessment, correlating functional and anatomical outcomes.

METHODS

This is a retrospective study performed in a tertiary referral center including 111 eyes from 95 CSC patients. Data on best corrected visual acuity (BCVA), central macular thickness (CMT), central retinal sensitivity (CRS) using microperimetry (MP) and multifocal electroretinography (mfERG) at baseline and 3, 6, 12, 18, 24, 36, 48 and 60 months after treatment were registered. A correlation analysis was performed.

RESULTS

Mean follow-up was 34.5 ± 26.3 months. A significant improvement in BCVA and CMT was registered in all the visits. CRS significantly improved until 24 months (p<0.001 at 12 months, p<0.05 at 24 months), worsening afterwards. The mfERG amplitude of N1 and P1 waves significantly improved in the first 12 months, aggravating afterwards. The implicit time improved until 24 months, deteriorating after 48 months. This long-term decline was also described in some inactive untreated fellow eyes CONCLUSIONS: : A multimodal longitudinal analysis of CSC patients after HD-PDT shows that, after the first 12 to 24 months, the significant sustained improvement in BCVA and CMT is not paired by a sustained improvement in macular sensitivity or electrical response. This long-term functional deterioration might result from the disease itself and not directly from the treatment.

Toward a clinical optoretinogram: a review of noninvasive, optical tests of retinal neural function

The past few years have witnessed rapid development of the optoretinogram-a noninvasive, optical measurement of neural function in the retina, and especially the photoreceptors (Ph). While its recent development has been rapid, it represents the culmination of hundreds of experiments spanning decades. Early work showed measurable and reproducible changes in the optical properties of retinal explants and suspensions of Ph, and uncovered some of the biophysical and biochemical mechanisms underlying them. That work thus provided critical motivation for more recent work based on clinical imaging platforms, whose eventual goal is the improvement of ophthalmic care and streamlining the discovery of novel therapeutics. The first part of this review consists of a selective summary of the early work, and identifies four kinds of stimulus-evoked optical signals that have emerged from it: changes in light scattered from the membranous discs of the Ph's outer segment (OS), changes in light scattered by the front and back boundaries of the OS, rearrangement of scattering material in and near the OS, and changes in the OS length. In the past decade, all four of these signals have continued to be investigated using imaging systems already used in the clinic or intended for clinical and translational use. The second part of this review discusses these imaging modalities, their potential to detect and quantify the signals of interest, and other factors influencing their translational promise. Particular attention is paid to phase-sensitive optical coherence tomography (OCT) with adaptive optics (AO), a method in which both the amplitude and the phase of light reflected from individual Ph is monitored as visible stimuli are delivered to them. The record of the light's phase is decoded to reveal a reproducible pattern of deformation in the OS, while the amplitude reveals changes in scattering and structural rearrangements. The method has been demonstrated in a few labs and has been used to measure responses from both rods and cones. With the ability to detect responses to stimuli isomerizing less than 0.01% of photopigment, this technique may prove to be a quick, noninvasive, and objective way to measure subtle disease-related dysfunction at the cellular level, and thus to provide an entirely new and complementary biomarker for retinal disease and recovery.

Multifocal Electroretinogram in Keratoconus Patients without and with Scleral Lenses

Purpose: To investigate changes in the multifocal electroretinogram (mfERG) response in eyes with keratoconus when corrected with scleral lenses (SL) compared with the best correction in glasses.Methods: The mfERG responses in 10 eyes with keratoconus were recorded with the best correction using both a trial frame (baseline) and a hexafocon A SL using an electrophysiological diagnostic system. Electrophysiologic measurements were performed with the pupils fully dilated with instillation of 1% phenylephrine. The implicit time (milliseconds), amplitude (nV), and response density (nV/deg²) of the peaks (N1, P1, and N2) were analyzed for the total mfERG response, six rings and four quadrants of the retina, and compared between the two conditions.Results: All eyes had a significant improvement in visual quality with the SL compared with baseline (mean differences, 0.26 ± 0.17 and 0.22 ± 0.13 logarithm of the minimum angle of resolution for high- and low-contrast visual acuity, respectively). The peaks implicit times of the mfERG responses did not show significant differences (p > .05). The P1 amplitude decreased in all the retinal areas with the SL. Only the total retinal response and the nasal quadrants reached significance (p ≤ 0.044). The P1 response density in ring 1 was on average higher with the SL, but not significantly so. The decline in P1 response density from the center to the periphery was more abrupt with the SL, and was more similar to the response density distribution of a typical subject, without a corneal pathology.Conclusions: mfERG did not show any change associated with retinal disease in young patients with keratoconus. Although the improved visual performance was not associated with changes in the mfERG response, the correction of irregular astigmatism with the SL helps exclude the optical effect induced by keratoconus.

[Performance evaluation of multifocal electroretinography for monocular and binocular stimulation in anisochromoartiphakia]

Multifocal electroretinography (mfERG) helps evaluate the electrical potential of the retina in a set of points within 30 degrees. There is a significant number of factors affecting the value of mfERG data, which should be taken into account in research studies.

PURPOSE

To evaluate the difference and nature of changes in the amplitude (P1) and latency (P1, L1) parameters of mfERG in monocular (MS) and binocular stimulation (BS) in individuals with anisochromoartiphakia.

MATERIAL AND METHODS

The study included 24 patients aged 76.3±7.9 years with anisochromoartiphakia [one eye - IOL with yellow spectrum SN60AT (yIOL); the other is a transparent IOL - Rayacryl (trIOL)] comprising the main group, and 16 patients without artiphakia aged 51.6±4.6 years in the control group [one eye with the addition of a yellow light filter (YF) ZHS1 - a spectral analog of SN60AT, the other - without YF]. Recording of mfERG was done with MS and BS. Parameters under evaluation were DP1 (nV/deg²), amplitude P1 (mV) and latency LP1, LN1 (ms) in rings R1-R5.

RESULTS

In general, when switching from one ring to another under both types of stimulation and spectral correction, all indicators decrease. DP1 and P1 in MS and BS in the control group (49.2±17.7 and 53.6±17.5 nV/deg²) compared to the main group were higher (42.9±15.0 and 47.7±17.3 nV/deg²), LP1 and LN1 were shorter (41.2±5.0 and 44.8±4.3 ms in the control group, 44.0±4.1 and 50.7±21.1 ms in the main group). There was a significant difference between DP1R3 and DP1R4 in the control group (p≤0.003-0.050). In the control group without YF, P1R2 under MS was statistically significantly higher than under BS (p≤0.028). LP1 of R1, R3, R5 in the intergroup comparison was statistically significantly shorter in the control group without YF and MS (p≤0.033) and with YF in R1-R3, R5 (p≤0.003-0.023). LP1R2, LP1R4 were statistically significantly higher with trIOL in the main group under MS (p≤0.015; 0.047) and with yIOL in LP1R1, LP1R4, and LR5 (p≤0.053). The intergroup comparison showed that in the main group with yIOL, LP1R5 was statistically significantly lower under MS than BS (p≤0.032). When comparing LN1 between the groups, the statistically significant difference under MS without YF was observed in R5 (p≤0.002), while the difference under BS was insignificant. For YF, the increase in LN1 was statistically significant for MS in R2 and R3 (p≤0.010; 0.037) and for BS - in R1, R2 and R4 (p≤0.037; 0.003; 0.020). The intergroup comparison revealed that in the control group without YF, LN1R2 was statistically significantly lower under MS than BS (p≤0.028), and in the main group with trIOL, LN1R3 under MS was statistically significantly lower than under BS (p≤0.041).

CONCLUSION

In anisochromoartiphakia, spectral differences in the optical environment of the eye lead to changes in the parameters of mfERG in the form of a decrease in DP1 and elongation of LP1 and LN1 in comparison with healthy eye and non-spectral intraocular correction. MS or BS in mfERG does not have a significant impact on the character and value of these parameters. The use of a single-stage binocular recording of mfERG reduces the duration of the study, which is especially important when examining elderly patients.

[Multifocal electroretinography in the study of focal and diffuse damage to the rabbit retina]

PURPOSE

To evaluate the possibility of using the system "Neuro-ERG" (with a module for multifocal ERG) in the study of focal and diffuse pathology in laboratory animals (rabbits).

MATERIAL AND METHODS

Focal retinal damage was modelled in 5 eyes of 5 rabbits by singular laser pulses (532 nm, 100 ms, power 30, 60, 100, 150 and 200 mW) and diffuse retinal damage was modelled in 5 eyes of 5 rabbits by exposure to polychromatic light for 14 days (9500 lm, 6400 K, 230 mW/cm2, 8 h/day). The pair of eyes and areas of intact retina in the eyes with focal retinal damage were used for control. Multifocal electroretinography (mfERG) was recorded using the «Neuro-ERG» system (Neurosoft, Russia) before exposure, after 1 hour (in focal damage model), and 1, 7 and 14 days after exposure. In addition, three-time recording of mfERG was made before and after the experiments. Analysis included the amplitude and time characteristics of mfERG components, as well as the level of reproducibility of mfERG at each recording.

RESULTS

In the modeling of focal damage of the rabbit retina, significant changes in mfERG (pattern stimulus consisted of 61 hexagons) were detected when the retinal damage area was more than 170 µm in diameter or more than 35% of the hexagon area in the pattern-stimulus. A significant moderate inverse correlation (0.52<r<0.71, p<0.01) was found between the damage area and the amplitude P1 and density of the bioelectric response of the P1 component. When modeling diffuse damage, significant changes in mfERG (an increase of implict-time of P1 and a decrease in the amplitude and density of the bioelectric response of the P1 component) were detected on the 7th day after the beginning of exposure. Variability of mfERG recording on each registration averaged 5%.

CONCLUSION

Multifocal ERG registration systems, including «Neuro-ERG» (Neurosoft, Russia), can be used in experimental studies of vitreoretinal pathology with rabbits as biological objects.

A review of electroretinography waveforms and models and their application in the dog

Electroretinography (ERG) is a commonly used technique to study retinal function in both clinical and research ophthalmology. ERG responses can be divided into component waveforms, analysis of which can provide insight into the health and function of different types and populations of retinal cells. In dogs, ERG has been used in the characterization of normal retinal function, as well as the diagnosis of retinal diseases and measuring effects of treatment. While many components of the recorded waveform are similar across species, dogs have several notable features that should be differentiated from the responses in humans and other animals. Additionally, modifications of standard protocols, such as changing flash frequency and stimulus color, and mathematical models of ERG waveforms have been used in studies of human retinal function but have been infrequently applied to visual electrophysiology in dogs. This review provides an overview of the origins and applications of ERG in addition to potential avenues for further characterization of responses in the dog.

Diagnostic ability of multifocal electroretinogram in early multiple sclerosis using a new signal analysis method

PURPOSE

To determine if a novel analysis method will increase the diagnostic value of the multifocal electroretinogram (mfERG) in diagnosing early-stage multiple sclerosis (MS).

METHODS

We studied the mfERG signals of OD (Oculus Dexter) eyes of fifteen patients diagnosed with early-stage MS (in all cases < 12 months) and without a history of optic neuritis (ON) (F:M = 11:4), and those of six controls (F:M = 3:3). We obtained values of amplitude and latency of N1 and P1 waves, and a method to assess normalized root-mean-square error (FNRMSE) between model signals and mfERG recordings was used. Responses of each eye were analysed at a global level, and by rings, quadrants and hemispheres. AUC (area under the ROC curve) is used as discriminant factor.

RESULTS

The standard method of analysis obtains further discrimination between controls and MS in ring R3 (AUC = 0.82), analysing N1 waves amplitudes. In all of the retina analysis regions, FNRMSE value shows a greater discriminating power than the standard method. The highest AUC value (AUC = 0.91) was in the superior temporal quadrant.

CONCLUSION

By analysing mfERG recordings and contrasting them with those of healthy controls it is possible to detect early-stage MS in patients without a previous history of ON.

Current perspectives in Bietti crystalline dystrophy

Bietti crystalline dystrophy (BCD) is a rare-inherited disease caused by mutations in the CYP4V2 gene and characterized by the presence of multiple shimmering yellow-white deposits in the posterior pole of the retina in association with atrophy of the retinal pigment epithelium (RPE) and chorioretinal atrophy. The additional presence of glittering dots located at the corneal limbus is also a frequent finding. The CYP4V2 protein belongs to the cytochrome P450 subfamily 4 and is mainly expressed in the retina and the RPE and less expressed in the cornea. The disease has its metabolic origin in the diminished transformation of fatty acid substrates into n-3 polyunsaturated fatty acids due to a dysregulation of the lipid metabolism. In this review, we provide updated insights on clinical and molecular characteristics of BCD including underlying mechanisms of BCD, genetic diagnosis, progress in the identification of causative genetic and epigenetic factors, available techniques of exploration and development of novel therapies. This information will help clinicians to improve accuracy of BCD diagnosis, providing the patient reliable information regarding prognosis and clinical prediction of the disease course.

Multifocal electroretinogram in eyes with intravitreal silicone oil and changes following silicone oil removal

PURPOSE

To determine the effect of intravitreal silicone oil (SO) on multifocal electroretinogram (mfERG) and the changes in mfERG following SO removal.

METHODS

Twelve eyes of 12 patients with SO in vitreous cavity with corrected distance visual acuity (CDVA) > 20/200 were prospectively enrolled as cases over a period from July 2016 to June 2018. The fellow normal eyes served as control. The eyes were evaluated with P1 and N1 wave amplitude and implicit time on mfERG at baseline, 1 and 4 weeks after SO removal.

RESULTS

The mean age was 44.9 ± 18.9 (range 18-74) years. The indication for SO injection was retinal detachment (n = 9, three macula-on eyes, six macula-off eyes) and endophthalmitis (n = 3). The median (range) LogMAR CDVA at baseline was 0.54 (0.18-0.78) in cases and did not change post-SO removal (p = 0.29). There was a significant decrease in average P1 and N1 wave amplitude (p = 0.0001 and 0.0001, respectively) and delay in average P1 and N1 wave implicit time (p = 0.0002 and 0.021, respectively) in cases as compared to controls. The macular status and duration of SO tamponade did not have a significant correlation with mfERG parameters. There was a significant increase in average P1 and N1 wave amplitude (p = 0.009 and 0.003, respectively) at 1 week following SO removal but no change in average P1 and N1 wave implicit time (p = 0.41 and 0.37, respectively).

CONCLUSION

mfERG may be reliably performed for the assessment of macular function in SO-filled eyes. Intravitreal SO exerts an insulating effect on the density of the electric potentials.

Five-Year Trends in Multifocal Electroretinogram for Patients With Birdshot Chorioretinopathy

PURPOSE

The aim of this study is to investigate temporal trends in multifocal ERG (mfERG) parameters and analyze their relationships with anatomic and functional markers in patients with birdshot chorioretinopathy (BSCR).

DESIGN

Prospective observational case series.

METHODS

Sixteen BSCR patients were include and underwent 2 standardized follow-up (FU) visits within 5 years following a baseline examination, including mfERG, visual acuity (VA), visual field (VF), Lanthony desaturated panel D-15 test for color vision, quality of life (QoL), fluorescein and indocyanine green angiography, and optical coherence tomography (OCT).

RESULTS

A significant trend toward a decrease in absolute N1 amplitude values was observed over the follow-up period (P < .001) while N1 implicit time remained unchanged. In contrast, P1 amplitude decreased (P < .001) and P1 implicit time increased (P < .001) over the same period. No significant temporal change was found for VA, color vision score, foveal threshold, mean deviation of VF, and QoL. After adjusting for time to FU, increasing N1 and P1 IT were both associated with decreasing values of logMAR, foveal threshold, and QoL and with increasing color vision score and mean deviation of VF. A significant relationship was observed between decreasing P1 amplitude values and increasing mean deviation of VF. Lower absolute values of N1 amplitude were associated with venous vasculitis, whereas lower P1 amplitude values correlated with alteration of the outer retina in OCT.

CONCLUSIONS

Progressive deterioration in mfERG during a 5-year period is detected in BSCR, whereas classical functional test results were unchanged. This study suggests a better sensitivity of mfERG in monitoring the retinal function of BSCR patients.

Human embryonic stem cell-derived retinal pigment epithelium transplants as a potential treatment for wet age-related macular degeneration

Stem cell therapy may provide a safe and promising treatment for retinal diseases. Wet age-related macular degeneration (wet-AMD) is a leading cause of blindness in China. We developed a clinical-grade human embryonic stem cell (hESC) line, Q-CTS-hESC-2, under xeno-free conditions that differentiated into retinal pigment epithelial cells (Q-CTS-hESC-2-RPE). A clinical trial with three wet-AMD patients was initiated in order to study the safety and tolerance to Q-CTS-hESC-2-RPE cell transplants. The choroidal neovascularization membrane was removed and then a suspension of 1 × 10⁶ Q-CTS-hESC-2-RPE cells were injected into a subfoveal pocket. The patients were followed for 12 months during which no adverse effects resulting from the transplant were observed. Anatomical evidence suggested the existence of new RPE-like cell layer in the previously damaged area. Visual and physiological testing indicated limited functional improvement, albeit to different degrees between patients. This study provides some promising early results concerning the use of transplanted hESC-RPE cells to alleviate wet-AMD.

Facilitating the analysis of the multifocal electroretinogram using the free software environment R

Purpose:

The large amount of data rendered by the multifocal electroretinogram (mfERG) can be analyzed and visualized in various ways. The evaluation and comparison of more than one examination is time-consuming and prone to create errors. Using the free software environment R we developed a solution to average the data of multiple examinations and to allow a comparison of different patient groups.

Methods:

Data of single mfERG recordings as exported in .csv format from a RETIport 21 system (version 7/03, Roland Consult) or manually compiled .csv files are the basis for the calculations. The R software extracts response densities and implicit times of N1 and P1 for the sum response, each ring eccentricity, and each single hexagon. Averages can be calculated for as many subjects as needed. The mentioned parameters can then be compared to another group of patients or healthy subjects. Application of the software is illustrated by comparing 11 patients with chloroquine maculopathy to a control group of 7 healthy subjects.

Results:

The software scripts display response density and implicit time 3D plots of each examination as well as of the group averages. Differences of the group averages are presented as 3D and grayscale 2D plots. Both groups are compared using the t-test with Bonferroni correction. The group comparison is furthermore illustrated by the average waveforms and by boxplots of each eccentricity.

Conclusions:

This software solution on the basis of the programming language R facilitates the clinical and scientific use of the mfERG and aids in interpretation and analysis.

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.

Genetics of Bietti Crystalline Dystrophy

Bietti crystalline dystrophy (BCD) is an inherited retinal degenerative disease characterized by crystalline deposits in the retina, followed by progressive atrophy of the retinal pigment epithelium (RPE), choriocapillaris, and photoreceptors. CYP4V2 has been identified as the causative gene for BCD. The CYP4V2 gene belongs to the cytochrome P450 superfamily and encodes for fatty acid ω-hydroxylase of both saturated and unsaturated fatty acids. The CYP4V2 protein is localized most abundantly within the endoplasmic reticulum in the RPE and is postulated to play a role in the physiological lipid recycling system between the RPE and photoreceptors to maintain visual function. Electroretinographic assessments have revealed progressive dysfunction of rod and cone photoreceptors in patients with BCD. Several genotypes have been associated with more severe phenotypes based on clinical and electrophysiological findings. With the advent of multimodal imaging with spectral domain optical coherence tomography, fundus autofluorescence, and adaptive optics scanning laser ophthalmoscopy, more precise delineation of BCD severity and progression is now possible, allowing for the potential future development of targets for gene therapy.

The Role of Multifocal Electroretinography in the Assessment of Drug-Induced Retinopathy: A Review of the Literature

Multifocal electroretinography (mfERG) is an objective, noninvasive examination for the assessment of visual function. It enables the stimulation of multiple retinal areas simultaneously and recording of each response independently, providing a topographic measure of retinal electrophysiological activity in the central 40-50° of the retina. A clinical application of mfERG represents the assessment of retinal toxicity associated with systemic medications. Drug-induced retinopathy represents a disease that, although not common, requires early recognition: if not detected early, it may progress and cause irreversible retinal dysfunction with subsequent visual impairment. This review aims to evaluate the use of mfERG in the assessment of retinal dysfunction associated with various systemic pharmacological agents based on the currently available literature. The most commonly recognized systemic medications affecting retinal function are included, such as chloroquine and hydroxychloroquine, vigabatrin, deferoxamine, ethambutol, interferon-α, tamoxifen, digoxin, sildenafil, canthaxanthin, amiodarone and nefazodone. The role of mfERG in the early diagnosis of retinal toxicity and the evaluation of disease severity is reviewed, as well as its clinical value in monitoring disease progression or recovery after drug cessation.

Local Relationship between Global-Flash Multifocal Electroretinogram Optic Nerve Head Components and Visual Field Defects in Patients with Glaucoma

Purpose. To investigate the local relationship between quantified global-flash multifocal electroretinogram (mfERG) optic nerve head component (ONHC) and visual field defects in patients with glaucoma. Methods. Thirty-nine patients with glaucoma and 30 normal controls were enrolled. The ONHC amplitude was measured from the baseline to the peak of the second positive deflection of the induced component. The ONHC amplitude was normalized by dividing ONHC amplitude by the average of seven largest ONHC amplitudes. The ONHC amplitude ratio map and ONHC deficiency map were constructed. The local relationship between the ONHC measurements and visual field defects was evaluated by calculating the overlap between the ONHC deficiency maps and visual field defect plots. Results. The mean ONHC amplitude measurements of patients with glaucoma (6.01 ± 1.91 nV/deg²) were significantly lower than those of the normal controls (10.29 ± 0.94 nV/deg²) (P < 0.001). The average overlap between the ONHC deficiency map and visual field defect plot was 71.4%. The highest overlap (75.0%) was between the ONHC ratios less than 0.5 and the total deviations less than 5%. Conclusions. The ONHC amplitude was reduced in patients with glaucoma compared to that in normal controls. Loss of the ONHC amplitude from the global-flash mfERG showed a high local agreement with visual field defects in patients with glaucoma.

Multifocal electroretinogram contributes to differentiation of various clinical pictures within a family with Bardet-Biedl syndrome

PURPOSE

To demonstrate the use of the multifocal electroretinogram (mfERG) in addition to the full-field electroretinogram (ERG) in defining varying clinical pictures in children within a family with Bardet-Biedl syndrome (BBS).

METHODS

All members from a family generation underwent a detailed history and examination before proceeding to a detailed ERG in accordance with the International Society of Clinical Electrophysiology for Vision protocol and a rapid, low-resolution mfERG. Of the sibling pair, the 13-year-old boy showed reduced vision and atypical maculopathy and the 10-year-old sister showed normal vision and atrophic maculopathy. Parents had normal ocular examination.

RESULTS

The male sibling had reduced rod and cone full-field ERG responses with a relatively spared central response from the mfERG suggesting central macular sparing. In contrast, for the female sibling, the ERG was normal for the cone pathway although reduced for rod pathway, with mfERG showing central involvement. The mother had rod responses at the lower end of normal range, a normal cone pathway, and a normal mfERG. The father showed a normal ERG and mfERG.

CONCLUSION

The mfERG is a useful adjunct to full-field ERG in the paediatric population and in family studies.

Early diagnosis of Stargardt disease with multifocal electroretinogram in children

To present two pediatric cases where multifocal electroretinogram (mfERG) was able to establish an earlier diagnosis compared to full field electroretinogram (ERG) Case 1: an 11-year-old boy with reduced visual acuity, pale discs, macular pigmentation with white dots bilaterally. Case 2: a 12-year-old girl with reduced vision in her right eye, slight pallor of the right optic disc, intense pigmentation at both maculae and scattered punctate lesions throughout the peripheral fundi. Both had been investigated with electrodiagnostic tests according to the International Society of Clinical Electrophysiology for Vision protocol. Full-field ERGs for both children showed normal responses. Case 1: mfERG revealed a severe reduction in function in the inner 20°. Case 2: mfERG showed attenuated responses in each eye. Clinical examination and mfERG were consistent with Stargardt disease. mfERG is applicable to children and is a sensitive tool for early diagnosis of retinal dystrophies.

Hydrochloroquine retinopathy: characteristic presentation with review of screening

Hydroxychloroquine (HCQ), an antimalarial drug in use since 1955, is still used with great success in the treatment of systemic lupus erythematosis and other rheumatological diseases. HCQ is generally well tolerated and its side effect profile confers many advantages over many other immunosuppressive agents. However, HCQ is known to induce retinopathy. Unfortunately, HCQ-induced retinopathy can present insidiously with subtle color vision changes and paracentral scotoma, which makes early detection difficult. Moreover, cessation of HCQ does not typically result in resolution of the visual loss, and vision loss may actually continue to progress even after HCQ is stopped. Therefore, identifying those patients most at risk for development of retinopathy is of the utmost importance, and adequate screening of patients taking HCQ is recommended. A brief case presentation of a patient who has developed retinal toxicity from hydroxychloroquine is provided along with a discussion regarding the characteristic retinopathy and review of current screening recommendations.

Prospects of Stem Cells for Retinal Diseases

Retinal diseases, including glaucoma, retinitis pigmentosa, diabetic retinopathy, and age-related macular degeneration, are the leading causes of irreversible visual impairment and blindness in developed countries. Traditional and current treatment regimens are based on surgical or medical interventions to slow down the disease progression. However, the number of retinal cells would continue to diminish, and the diseases could not be completely cured. There is an emerging role of stem cells in retinal research. The stem cell therapy on retinal diseases is based on 2 theories: cell replacement therapy and neuroprotective effect. The former hypothesizes that new retinal cells could be regenerated from stem cells to substitute the damaged cells in the diseased retina, whereas the latter believes that the paracrine effects of stem cells modulate the microenvironments of the diseased retina so as to protect the retinal neurons. This article summarizes the choice of stem cells in retinal research. Moreover, the current progress of retinal research on stem cells and the clinical applications of stem cells on retinal diseases are reviewed. In addition, potential challenges and future prospects of retinal stem cell research are discussed.

mfERG_LAB: Software for processing multifocal electroretinography signals

The multifocal electroretinography technique consists of performing sectorized light excitation of the retina and capturing the resulting evoked potential. This provides functional localized information about the state of the retinal neurons. Analysis of multifocal electroretinography signals can be used for diagnosing different types of optic neuropathies (glaucomatous, demyelinating and ischemic ethiology). In order to obtain a reliable diagnosis, it is necessary to apply advanced processing algorithms (morphological, frequency and time-frequency analysis, etc.) to the multifocal electroretinography signal. This paper presents a software application developed in MATLAB(®) (MathWorks Inc., MA) designed to perform advanced multifocal electroretinography signal analysis and classification. This intuitive application, mfERG_LAB, is used to plot the signals, apply various algorithms to them and present the data in an appropriate format. The application's computational power and modular structure make it suitable for use in clinical settings as a powerful and innovative diagnostic tool, as well as in research and teaching settings as a means of assessing new algorithms.

Retinal neuropathy precedes vasculopathy in diabetes: a function-based opportunity for early treatment intervention?

Diabetes, now at epidemic levels, can have devastating effects on the eye and vision. Treatments of the ocular complications are currently focused on relatively advanced stages and are limited to the slowing down of the progressive sight-threatening retinal vasculopathy (diabetic retinopathy). Tiny signals from the neural retina have been shown to reveal early diabetic neuropathy prior to vascular retinopathy. These signals, in a clinical test format, are predictive, by precise retinal location, of impending vasculopathy in the retina within a year, including sight-threatening oedema. The discovery opens possibilities for the future development of treatments to prevent the onset of retinopathy and the more sight-threatening retinal oedema and changes patient management strategies.

Multifocal electroretinogram in normal emmetropic subjects: correlation with optical coherence tomography

Aim of the Study:

To establish the normative database for multifocal electroretinogram (mfERG) parameters in a normal emmetropic population. To correlate the data so obtained with the central macular thickness obtained using the optical coherence tomography (OCT) scan.

Materials and Methods:

mfERG data were obtained from 222 eyes of 111 emmetropic subjects. The amplitude (nv/deg²) and implicit times (ms) of the first-order kernel mfERG responses (N1, P1, and N2 waves) were obtained and grouped into five rings (Ring 1: Central 2°, Ring 2: 2–5°, Ring 3: 5–10°, Ring 4: 10–15°, Ring 5: >15°). The central macular thickness (CMT) was obtained using the macular thickness scan protocol of the OCT.

Results:

The mfERG data obtained were used to create a normative database. The amplitudes of the mfERG waves were maximum in the fovea and progressively decreased with increasing eccentricity (P = 0.0001). The latencies of the P1 and N2 waves were longest in the central ring and progressively shortened with eccentricity (P = 0.0001). No statistically significant correlations were observed between central ring 1 parameters and the CMT.

Conclusion:

This study establishes normative database for mfERG parameters in an emmetropic population. No statistically significant correlation was noted between CMT and mfERG parameters.

Macular structure and function and the development of retinopathy in diabetes

BACKGROUND

The aim of this study was to evaluate the relationship between structural and functional changes identified with the Rarebit fovea test (RFT) in diabetic patients over two years. In addition, we evaluated whether the RFT changes at baseline can predict vascular changes detectable by conventional screening methods four to six years later.

METHODS

Forty-two patients with diabetes and 42 age-matched healthy subjects underwent an initial examination. Two years later, 25 of the diabetic patients and 20 of the controls were re-examined in the same way. Four to six years later, 40 of the diabetic patients underwent a standard screening examination including fundus photography. After two years, all subjects were examined with the RFT and visual acuity (VA) was assessed. In addition, optical coherence tomography (OCT) and fundus photography were performed on the diabetic patients. At a screening examination of the diabetic patients after four to six years, fundus photographs were reviewed.

RESULTS

After two years, a marked difference in RFT results was observed between the 20 normal subjects and the 25 patients with diabetes. Results from other tests (VA and central retinal thickness, as measured with OCT) were unchanged compared with the initial examinations. Fundus photography four to six years later of 40 of the 42 diabetic patients showed an increased incidence of retinopathy unrelated to the RFT findings at baseline.

CONCLUSIONS

The findings in the current study indicate that the RFT might detect macular dysfunction in diabetic eyes without microvascular changes. This dysfunction increased during a two-year period and presumably reflects neural impairment in diabetes mellitus but did not predict development of retinopathy during the four to six year period.

Investigation of the temporal properties of the retina using the m-sequence

The mfERG provides a topographic map of function of the retina and has been used in numerous studies to identify macular, paramacular and peripheral retinal dysfunction. This study investigates the changes in response due to the presentation rate of the stimulus. Twenty subjects gave informed consent to take part in the study, which had local regional ethical committee approval. Only a single hexagon of 8° diameter was presented to reduce ambiguity when identifying the higher-order kernels (HOK). Six rates were tested using a 60-Hz CRT monitor by introducing blank (black ~0 cd/m2) filler frames (FF). The rates tested were 0FF; 1FF; 2FF; 4FF; 7FF; and 14FF. The first-order kernel had largest responses to the slower stimuli (4FF and above). HOK had largest amplitudes at faster rates with the second-order kernel peaking at 1FF. At rates with 4FF and slower, the higher-order kernels were indiscernible above the noise.

Application of multifocal visual evoked potentials in the assessment of visual dysfunction in macular diseases

PURPOSE

To evaluate the use of AccuMap multifocal visual evoked potentials (mfVEP) in visual dysfunction caused by macular diseases.

METHODS

Forty-eight eyes with known macular diseases underwent AccuMap mfVEP and microperimetry 1 (MP1) assessments. Evaluation of mfVEP abnormality was based on an amplitude deviation probability plot and the AccuMap Severity Index (ASI). Correlation analyses of the mean mfVEP amplitude corresponding to a radius of 2°, 5°, and 10° of the central visual field, minimum angle of resolution best-corrected visual acuity (BCVA), and MP1 mean sensitivity of the corresponding areas were performed.

RESULTS

Among the 48 affected eyes, AccuMap mfVEP detected an abnormality of the central visual field in 45 eyes, with a sensitivity of 93.8%. The mean mfVEP amplitudes within a radius of 2°, 5°, and 10° of the central visual field were found to be positively correlated with BCVA (P<0.01 for all groups). The mean amplitudes also positively correlated with the MP1 mean sensitivity value of the corresponding visual field (P<0.01 for all groups). In the group with stable fixation or predominantly central fixation, the mean mfVEP amplitudes did not correlate with the BCVA or the MP1 mean sensitivity value. Regardless of the fixation status, the ASI was found to correlate with both the BCVA and the total MP1 mean defect value.

CONCLUSION

Objective perimetry using AccuMap mfVEP might be applied in the assessment of macular function, with the ASI offering a potentially useful indicator for evaluating macular dysfunction.

Loss of the low-frequency component of the global-flash multifocal electroretinogram in primate eyes with experimental glaucoma

PURPOSE

To study relationships between glaucoma-sensitive components identified with frequency-domain analysis of global-flash multifocal electroretinogram (mfERG), regional retinal nerve fiber layer thickness (RNFLT), and local visual field sensitivity (VS).

METHODS

Eleven macaque monkeys, including four controls and seven with unilateral laser-induced trabecular meshwork scarification and ocular hypertension, were observed with optical coherence tomography (OCT), full-field light-adapted flash ERG, 103-hexagon global-flash mfERG (MFOFO), and static perimetry. The effects of experimental glaucoma on mfERG were assessed in the frequency domain. Relations between root mean square (RMS) amplitude of a glaucoma-sensitive frequency range and peripapillary RNFLT (standard 12° OCT circular scan), and between RMS amplitude and VS were studied.

RESULTS

Experimental glaucoma led to a dramatic and consistent power loss in the low-frequency (<25 Hz) band of mfERG. The RMS of this low-frequency component (LFC) correlated significantly with the regional RNFLT. The r(2) of linear fits was 0.39 (P < 0.001) for cross-sectional group data and 0.60 after correction for intersubject variability. The r(2) of linear fits for longitudinal data from individual animals was as high as 0.78 (P < 0.001). Local LFC RMS amplitude also correlated significantly with interpolated VS for hexagons. The r(2) for exponential fits of hexagon LFC RMS amplitudes (inner three rings) versus VS (dB) was 0.29 to 0.52 (P < 0.001) for the group and up to 0.95 in individuals.

CONCLUSIONS

The significant correlations between regional measures of global-flash mfERG, RNFLT, and VS suggest that LFC RMS amplitude provides a useful index for objective quantification of local RGC function and monitoring of early changes in glaucoma.

The neuro-ophthalmological examination

The neuro-ophthalmological examination constitutes one of the most refined and exact components of the clinical examination, often allowing precise diagnosis and formulation of a treatment plan even within the compass of the first visit. This chapter briefly highlights important features in the neuro-ophthalmological history and then presents detailed information on the important components of a comprehensive neuro-ophthalmological examination. Covered examination topics include visual acuity, visual field testing, color vision, external eye exam, pupils, ophthalmoscopy, and eye movements. The final section discusses ancillary tests that supplement the bedside neuro-ophthalmological examination, including formal visual field analysis, electroretinography, fluorescein angiography, ocular coherence tomography, visual-evoked potentials, neuroimaging, and quantitative eye movement recordings.

Multifocal electroretinography

Multifocal electroretinography (mfERG) provides functional and objective evidence of retinal dysfunction. We have found mfERG to be especially useful in the management of occult outer retinopathy and Stargardt's disease.

Correlation between functional and anatomical assessments by multifocal electroretinography and optical coherence tomography in central serous chorioretinopathy

To evaluate the correlation between functional and anatomical assessments with multifocal electroretinography (mfERG) and optical coherence tomography (OCT) in patients with acute central serous chorioretinopathy (CSC). Thirty-four eyes of 34 patients with acute CSC underwent mfERG and OCT examinations. First-order mfERG N1 and P1 response amplitudes and latencies were analyzed.OCT parameters measured included central subretinal fluid (SRF) thickness, central retinal thickness, total central foveal thickness, vertical, and horizontal diameters of SRF, and macular volume. Correlation analyses were performed between best-corrected visual acuity (BCVA), mfERG parameters, and OCT measurements. Correlation analysis showed that logMAR BCVA was significantly correlated with mfERG N1 amplitudes of rings 1 and 2 (P = 0.006), N1 latency of ring 4 (P = 0.012), and P1 latency of ring 1 (P = 0.036). No significant correlation was observed between logMAR BCVA and any of the OCT measurements. For the correlation between mfERG parameters and OCT measurements, mfERG N1 and P1 latencies of the paracentral rings were significantly correlated with the central SRF thickness (P < or = 0.024), diameters of the SRF (P < or = 0.018), and macular volume (P < or = 0.030). MfERG responses but not OCT measurements correlated with logMAR BCVA in patients with acute CSC. The amount of SRF nonetheless correlated with the mfERG N1 and P1 latencies of the paracentral rings, suggesting that impairment in the conduction of electrical responses in the paracentral macula is proportional to the severity of serous macular detachment in CSC. MfERG and OCT can complement each other in the functional and anatomical assessments in CSC.

Unilateral choroidal excavation in the macula detected by spectral-domain optical coherence tomography

PURPOSE

To report clinical findings of three patients with unilateral peculiar choroidal excavation in the macula detected by spectral-domain (SD) optical coherence tomography (OCT).

METHODS

Three cases with unilateral choroidal excavation in the macula detected by SD OCT. Fluorescein angiography (FA), indocyanine green angiography (IA), ultrasonography, visual field tests and multifocal electroretinography (mfERG) were performed.

RESULTS

Although all three patients complained of metamorphopsia, visual acuity and central visual field were normal in the affected eyes. SD OCT demonstrated choroidal excavation in the macula despite a normal foveal contour along the inner retinal surface. The excavation involved the outer retinal layers up to the external limiting membrane in cases 1 and 2, while only the retinal pigment epithelium was involved in case 3. The excavation corresponded to foveal pigment mottling in cases 1 and 2 and to a parafoveal yellowish fusiform lesion in case 3. The lesions appeared hypoautofluorescent and unremarkable in FA except for circumferential hyperfluorescence in case 3 and hypofluorescent in IA. B-scan ultrasonography was unremarkable. MfERG in cases 1 and 2 was normal.

CONCLUSIONS

SD OCT demonstrated two types of choroidal excavation in the macula. More case accumulation and a longer follow-up will elucidate the pathogenesis and prognosis of the lesions.

The electroretinogram: a useful tool for evaluating age-related macular disease?

With an ageing population, the number of age-related macular disease (ARMD) cases will inevitably rise. This gives greater impetus for the need to identify the disease earlier and assess treatments to slow disease progression. Differing electroretinogram (ERG) modalities have been reviewed in relation to the objective assessment of retinal function in ARMD and for monitoring the effectiveness of clinical interventions. Conflicting results have been found with regard to the efficacy of ERG findings in the investigation of ARMD in previous years. The newer multifocal ERG paradigm provides spatial topographical information about retinal function in ARMD. It has shown promising results in monitoring effectiveness of clinical interventions and studies are continuing in this area. Better knowledge of retinal function in ARMD may lead to enhanced treatments at each phase of the disease.