Electroretinogram findings in unilateral optic neuritis

Electrodiagnostic tests of the visual pathway and applications in neuro-ophthalmology

This article describes the main visual electrodiagnostic tests relevant to neuro-ophthalmology practice, including the visual evoked potential (VEP), and the full-field, pattern and multifocal electroretinograms (ffERG; PERG; mfERG). The principles of electrophysiological interpretation are illustrated with reference to acquired and inherited optic neuropathies, and retinal disorders that may masquerade as optic neuropathy, including ffERG and PERG findings in cone and macular dystrophies, paraneoplastic and vascular retinopathies. Complementary VEP and PERG recordings are illustrated in demyelinating, ischaemic, nutritional (B12), and toxic (mercury, cobalt, and ethambutol-related) optic neuropathies and inherited disorders affecting mitochondrial function such as Leber hereditary optic neuropathy and dominant optic atrophy. The value of comprehensive electrophysiological phenotyping in syndromic diseases is highlighted in cases of SSBP1-related disease and ROSAH (Retinal dystrophy, Optic nerve oedema, Splenomegaly, Anhidrosis and Headache). The review highlights the value of different electrophysiological techniques, for the purposes of differential diagnosis and objective functional phenotyping.

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

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

B cell-dependent EAE induces visual deficits in the mouse with similarities to human autoimmune demyelinating diseases

BACKGROUND

In the field of autoimmune demyelinating diseases, visual impairments have extensively been studied using the experimental autoimmune encephalomyelitis (EAE) mouse model, which is classically induced by immunization with myelin oligodendrocyte glycoprotein peptide (MOG35-55). However, this model does not involve B cells like its human analogs. New antigens have thus been developed to induce a B cell-dependent form of EAE that better mimics human diseases.

METHODS

The present study aimed to characterize the visual symptoms of EAE induced with such an antigen called bMOG. After the induction of EAE with bMOG in C57BL/6J mice, visual function changes were studied by electroretinography and optomotor acuity tests. Motor deficits were assessed in parallel with a standard clinical scoring method. Histological examinations and Western blot analyses allowed to follow retinal neuron survival, gliosis, microglia activation, opsin photopigment expression in photoreceptors and optic nerve demyelination. Disease effects on retinal gene expression were established by RNA sequencing.

RESULTS

We observed that bMOG EAE mice exhibited persistent loss of visual acuity, despite partial recovery of electroretinogram and motor functions. This loss was likely due to retinal inflammation, gliosis and synaptic impairments, as evidenced by histological and transcriptomic data. Further analysis suggests that the M-cone photoreceptor pathway was also affected.

CONCLUSION

Therefore, by documenting visual changes induced by bMOG and showing similarities to those seen in diseases such as multiple sclerosis and neuromyelitis optica, this study offers a new approach to test protective or restorative ophthalmic treatments.

Comparison of the Structure and Function of the Retina and the Optic Nerve in Patients with a History of Multiple Sclerosis-Related Demyelinating Retrobulbar Optic Neuritis Treated and Not Treated with Systemic Steroid Therapy

Purpose

To compare the structure and function of the retina and the optic nerve in patients with a history of multiple sclerosis (MS)-related demyelinating retrobulbar optic neuritis treated and not treated with systemic steroid therapy.

Patients and Methods

Thirty-two eyes of 32 MS patients with a past single episode of MS-related demyelinating retrobulbar ON were divided into 2 groups: S(+) consisting of 16 patients treated with intravenous methylprednisolone at a dose of 1g/day for 3 days during the acute stage of ON and S(-) consisting of 16 patients who did not receive any treatment. The following examinations were performed: distance best-corrected visual acuity (DBCVA) (Snellen), slit-lamp examination of the anterior and posterior segment of the eye (90D Volk lens), visual field analysis (Carl Zeiss Humphrey 750 Visual Field Analyzer, 24-2, W-W), macular thickness in the foveal (RT1) and parafoveal region (RT2), as well as peripapillary retinal nerve fiber layer thickness (RNFL) in the temporal, superior, nasal and inferior quadrants (Carl Zeiss Cirrus HD-OCT), assessment of the bioelectrical function of the visual pathway with an emphasis on the optic nerve - pattern visual evoked potentials (PVEP) and of macular ganglion cells and cone photoreceptors - pattern electroretinogram (PERG) (Roland Consult).

Results

No statistically significant differences were observed between the investigated groups in terms of DBCVA, mean deviation of visual field macular (RT1, RT2) and RNFL thickness in the temporal, superior, nasal and inferior quadrants, as well as of the bioelectrical function (PVEP, PERG).

Conclusion

The application of steroid therapy should be considered on an individual basis and not as a routine treatment for each patient.

Electrophysiology in neuro-ophthalmology

This chapter reviews common applications of visual electrophysiology relevant to neuro-ophthalmology practice. The use of standard tests and extended protocols are described including the cortical visual evoked potential and pattern and full-field electroretinogram (PERG; ERG) methods, the latter including the photopic negative response. Abnormalities of these recordings are rarely specific but provide valuable diagnostic guidance and an objective measure of visual pathway function, difficult or impossible to infer by other methods. The electrophysiological phenotypes associated with Leber hereditary optic neuropathy, OPA1- and SSBP1-associated dominant optic atrophy, and WFS1-related syndromes are described. Typical changes in retinal and optic nerve function tests associated with acquired disease are highlighted, including those related to demyelination, ischemic, compressive, nutritional and toxic, and nonorganic etiologies. The importance of complementary testing using different electrophysiological techniques is emphasized, for the purposes of differential diagnosis and in disorders that may masquerade as optic nerve pathology.

Chromatic visual evoked potentials indicate early dysfunction of color processing in young patients with demyelinating disease

PURPOSE

Chromatic visual evoked potentials (cVEP) primarily reflect the parvocellular visual pathway function, which has been shown to be predominantly affected in demyelinating disease (DD). The purpose of this study was to evaluate cVEP responses and to compare them with other structural and functional findings in young patients with DD.

METHODS

Thirty patients (8-28 years of age) with DD with or without a history of optic neuritis (ON) were investigated. Twenty-five eyes had at least one episode of ON (ON-group) and 35 eyes had no clinically evident episode of ON (nON-group). OCT imaging was performed using a high-resolution spectral-domain OCT (SD-OCT), measuring retinal nerve fiber layer (RNFL) thickness. Pattern reversal electroretinography (PERG) and visual evoked potentials (VEP) were recorded according to the ISCEV standard, and chromatic visual evoked potentials (cVEP) were recorded to isoluminant red-green (R-G) and blue-yellow (B-Y) 7° circle stimuli, composed of horizontal sinusoidal gratings with spatial frequency 2 cycles/°, 90% chromatic contrast and onset-offset (300:700 ms) mode of stimulation. Structural and functional measures were analyzed and compared between the groups.

RESULTS

Both general (G) and temporal (T) RNFL thicknesses were reduced below normal limits in most of the eyes. However, in the ON-group (G: 77.5 ± 20.6, T: 51.4 ± 23.4 µm), the thinning was more significant (p < 0.001) than in the nON-group (G: 95.4 ± 12.1, T: 70.1 ± 11.5 µm). PERG N95 was within normal limits in the nON-group, while it was significantly more affected in the ON-group (7.4 ± 1.0 vs. 5.1 ± 2.0 μV; p < 0.0001). Similarly, also VEP P100 latency and amplitude showed a greater percentage of abnormality in the ON-group, the latency being longer (117.2 ± 16.9 vs. 99.4 ± 4.6 ms; p < 0.0001) and the amplitude lower (9.1 ± 5.1 vs. 16.4 ± 7.5 μV; p < 0.0001). The cVEP N-wave amplitude to R-G and B-Y stimuli was reduced below normal limits in both ON- and nON-groups; however, cVEP to B-Y stimulation were slightly more affected in the ON-group (4.0 ± 3.8 vs. 5.9 ± 3.3 µm; p = 0.02). A positive correlation between cVEP amplitude and RNFL thickness and between cVEP amplitude and PERG N95 amplitude, as well as a strong negative correlation between cVEP amplitude and P100 latency was observed.

CONCLUSIONS

These findings demonstrate that cVEP indicate early abnormality of parvocellular pathway function in eyes with or without a history of optic neuritis and can be used together with other structural and functional parameters to evaluate visual pathway integrity of young patients with DD.

Outer Retinal Dysfunction on Multifocal Electroretinography May Help Differentiating Multiple Sclerosis From Neuromyelitis Optica Spectrum Disorder

Purpose: To evaluate the intermediate and outer retina of patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) using OCT and multifocal electroretinography (mf-ERG). Methods: Patients with MS (n = 30), NMOSD (n = 30), and healthy controls (n = 29) underwent visual field (VF), OCT, and mf-ERG testing. The eyes were distributed into 5 groups: MS with or without history of ON (MS+ON, MS-ON), NMOSD with or without ON (NMOSD+ON, NMOSD-ON), and controls. The thickness of the macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer, outer plexiform layer, outer nuclear layer, and photoreceptor layer was measured. mf-ERG P1 and N1 responses were registered and grouped in 3 sets of rings. The groups were compared using GEE models, and effect size (ES) calculated. Results: Compared to controls, GCL and IPL thickness was significantly smaller in MS+ON (both p < 0.01), MS-ON (p < 0.01 and p = 0.015, respectively), NMOSD+ON (both p < 0.01) and NMOSD-ON (p = 0.03 and p = 0.018, respectively). ES was >0.80. mRNFL was smaller in three of the above groups (p < 0.01, p < 0.001, and p = 0.028; ES > 0.80) but not in MS-ON eyes (p = 0.18). No significant difference was observed for the remaining layers. Compared to controls, P1 and N1 peak times were shorter in MS (p-values in the range 0.049-0.002, ES < 0.50; and 0.049-0.010; ES < 0.50, respectively) but not in NMOSD. These abnormalities were strongly correlated with intermediate and outer retinal layer thickness. Conclusions: mf-ERG data suggest outer retinal abnormalities in MS, but not in NMOSD. Our results may help understand how the two conditions differ regarding retinal damage.

Decoding PERG: A neuro-ophthalmic retinal ganglion cell function review

Purpose of review

Currently, the clinical evaluation of neuro-ophthalmologic diseases are mainly focused on identifying stages where structural or functional damage occur. Recognition of retinal ganglion cell (RGC) functional patterns as well as monitoring RGC dysfunction can be performed using steady-state pattern electroretinogram (PERG). The analysis of the amplitude and latency shift aid on providing information on early damage or monitoring of the RGC, allowing for prompt clinical intervention and management modification, potentially changing the natural history of the disease. The purpose of this article is to review the latest findings in PERG, in early manifest glaucoma, non arteritic ischemic optic neuropathy, multiple sclerosis with unilateral recovered optic neuritis and its fellow eyes.

Recent Findings

The steady-state PERG responses provide new and early specific information in neuro-ophthalmic diseases affecting the inner retina.

Summary

Steady state PERG presents specific amplitude and latency outcomes based on the neuro-ophthalmic disease affecting the inner retina, allowing early recognition of changes at the level of RGC and the degree of RGC dysfunction. In addition, PERG alterations may be induced in healthy subjects as well as susceptible eyes using different stress tests such as head down tilting or water drinking tests.

Neuroprotection and visual function after optic neuritis

PURPOSE OF REVIEW

This article discusses the advantages and pitfalls of testing neuroprotective treatment strategies in patients suffering from optic neuritis.

RECENT FINDINGS

Spectral domain optical coherence tomography now permits for automated segmentation of individual retinal layers. The peripapillary retinal nerve fibre layer (pRNFL) has been used in 13 of the 15 trials reviewed. Twelve trials also made use of electrophysiology. Overestimation of good visual recovery in the past has recently been recognized. Assessment of low contrast visual acuity and colour vision are now mainstream.

SUMMARY

The availability of highly accurate and robust trial outcome measures has facilitated research on this topic. A single long-term structural outcome measurement of the pRNFL is sufficient. For shorter term, assessments of the ganglion cell/inner plexiform layer and axonal birefringence are promising. Longitudinal blood levels of neurofilament proteins permit to recognize axonal loss at presentation and monitor changes longitudinally. Inner nuclear layer volume changes relate to inflammatory disease activity.Pitfalls are related to the timing of events. Hyperacute recruitment is needed for future trials. The onset of demyelination is not known, which complicates timing of electrophysiological recordings. Optic disc oedema precludes the use of the pRNFL from the affected eye as a baseline variable. The concomitant use of corticosteroids complicates interpretation of trial data.

Progressive inner nuclear layer dysfunction in non-optic neuritis eyes in MS

OBJECTIVE

To investigate primary retinal functional changes in non-optic neuritis (ON) eyes of patients with MS by full-field electroretinography (ERG).

METHODS

Seventy-seven patients with relapsing-remitting MS with no history of clinical ON in at least 1 eye and 30 healthy controls were recruited in the cohort study. Full-field ERGs were recorded, and retinal optical coherence tomography scans were performed to assess the thicknesses of peripapillary retinal nerve fiber layer (RNFL) and retinal ganglion cell layer-inner plexiform layer (GCL-IPL). Annual MRI scans were also carried out to evaluate the disease activity in the brain. Patients were followed up for 3 years.

RESULTS

At baseline, a delayed b-wave peak time was observed in the cone response (p < 0.001), which was associated with the thicknesses of RNFL and GCL-IPL. The peak time of the delayed b-wave also correlated with the Expanded Disability Status Scale, T2 lesion volume, and disease duration. During the 3-year follow-up, progressive ERG amplitude reduction was observed (both a- and b-waves, p < 0.05). There was a correlation between the b-wave amplitude reduction and longitudinal RNFL loss (p = 0.001). However, no correlation was found between longitudinal ERG changes and disease activity in the brain.

CONCLUSIONS

This study demonstrated progressive inner nuclear layer dysfunction in MS. The borderline a-wave changes suggested some outer retinal dysfunction as well. The correlation between full-field ERG changes and retinal ganglion cell loss suggested that there might be subclinical retinal pathology in MS affecting both outer and inner retinal layers.

Efferent influences on the bioelectrical activity of the retina in primates

PURPOSE

The existence of retinopetal (sometimes referred to as "efferent" or "centrifugal") axons in the mammalian optic nerve is a topic of long-standing debate. Opposition is fading as efferent innervation of the retina has now been widely documented in rodents and other animals. The existence and function of an efferent system in humans and non-human primates has not, though, been definitively established. Such a feedback pathway could have important functional, clinical, and experimental significance to the field of vision science and ophthalmology.

METHODS

Following a comprehensive literature review (PubMed and Google Scholar, until July 2016), we present evidence regarding a system that can influence the bioelectrical activity of the retina in primates.

RESULTS

Anatomical and physiological evidences are presented separately. Improvements in histological staining and the advent of retrograde nerve fiber tracers have allowed for more confidence in the identification of efferent optic nerve fibers, including back to their point of origin.

CONCLUSION

Even with the accumulation of more modern anatomical and physiological evidence, some limitations and uncertainties about crucial details regarding the origins and role of a top-down, efferent system still exist. However, the summary of the evidence from earlier and more modern studies makes a compelling case in support of such a system in humans and non-human primates.

Amiloride Clinical Trial In Optic Neuritis (ACTION) protocol: a randomised, double blind, placebo controlled trial

INTRODUCTION

Neurodegeneration is a widely accepted contributor to the development of long-term disability in multiple sclerosis (MS). While current therapies in MS predominantly target inflammation and reduce relapse rate they have been less effective at preventing long-term disability. The identification and evaluation of effective neuroprotective therapies within a trial paradigm are key unmet needs. Emerging evidence supports amiloride, a licenced diuretic, as a neuroprotective agent in MS through acid sensing ion channel blockade. Optic neuritis (ON) is a common manifestation of MS with correlates of inflammation and neurodegeneration measurable within the visual pathways. Amiloride Clinical Trial In Optic Neuritis (ACTION) will utilise a multimodal approach to assess the neuroprotective efficacy of amiloride in acute ON.

METHODS AND ANALYSIS

46 patients will be recruited within 28 days from onset of ON visual symptoms and randomised on a 1:1 basis to placebo or amiloride 10 mg daily. Double-blinded treatment groups will be balanced for age, sex and visual loss severity by a random-deterministic minimisation algorithm. The primary objective is to demonstrate that amiloride is neuroprotective in ON as assessed by scanning laser polarimetry of the peripapillary retinal nerve fibre layer (RNFL) thickness at 6 months in the affected eye compared to the unaffected eye at baseline. RNFL in combination with further retinal measures will also be assessed by optical coherence tomography. Secondary outcome measures on brain MRI will include cortical volume, diffusion-weighted imaging, resting state functional MRI, MR spectroscopy and magnetisation transfer ratio. In addition, high and low contrast visual acuity, visual fields, colour vision and electrophysiology will be assessed alongside quality of life measures.

ETHICS AND DISSEMINATION

Ethical approval was given by the south central Oxford B research ethics committee (REC reference: 13/SC/0022). The findings from ACTION will be disseminated through peer-reviewed publications and at scientific conferences.

TRIAL REGISTRATION NUMBER

EudraCT2012-004980-39, ClinicalTrials.gov Identifier: NCT01802489.

Re-evaluating the treatment of acute optic neuritis

Clinical case reports and prospective trials have demonstrated a reproducible benefit of hypothalamic-pituitary-adrenal (HPA) axis modulation on the rate of recovery from acute inflammatory central nervous system (CNS) demyelination. As a result, corticosteroid preparations and adrenocorticotrophic hormones are the current mainstays of therapy for the treatment of acute optic neuritis (AON) and acute demyelination in multiple sclerosis.Despite facilitating the pace of recovery, HPA axis modulation and corticosteroids have failed to demonstrate long-term benefit on functional recovery. After AON, patients frequently report visual problems, motion perception difficulties and abnormal depth perception despite 'normal' (20/20) vision. In light of this disparity, the efficacy of these and other therapies for acute demyelination require re-evaluation using modern, high-precision paraclinical tools capable of monitoring tissue injury.In no arena is this more amenable than AON, where a new array of tools in retinal imaging and electrophysiology has advanced our ability to measure the anatomic and functional consequences of optic nerve injury. As a result, AON provides a unique clinical model for evaluating the treatment response of the derivative elements of acute inflammatory CNS injury: demyelination, axonal injury and neuronal degeneration.In this article, we examine current thinking on the mechanisms of immune injury in AON, discuss novel technologies for the assessment of optic nerve structure and function, and assess current and future treatment modalities. The primary aim is to develop a framework for rigorously evaluating interventions in AON and to assess their ability to preserve tissue architecture, re-establish normal physiology and restore optimal neurological function.

A phenotype-genotype correlation study of X-linked retinoschisis

PURPOSE

To compare the clinical phenotype and detailed electroretinographic parameters in X-linked retinoschisis (XLRS).

DESIGN

Retrospective, comparative study.

PARTICIPANTS

Fifty-seven patients (aged 1-67 years) with molecularly confirmed XLRS were clinically ascertained.

METHODS

Pattern electroretinography (PERG) and full-field electroretinography (ERG), incorporating international standard recordings, were performed in 44 cases. Thirteen patients, mostly pediatric, were tested using a simplified ERG protocol. On-Off and S-cone ERGs were performed in most adults. Fundus autofluorescence (FAF) imaging and optical coherence tomography (OCT) were available in 17 and 21 cases, respectively.

MAIN OUTCOME MEASURES

The clinical and electrophysiologic data associated with different types of mutation in the RS1 gene.

RESULTS

Forty-three patients had missense changes (group A), and 14 patients had nonsense, splice-site, or frame-shifting mutations in the RS1 gene (group B). The mean best-corrected visual acuity was better in group A than in group B (0.34 and 0.21, respectively). Fundus examination revealed foveal schisis in approximately half of both groups. The bright-flash dark-adapted (DA) ERG (11.0 candela.sec.m(-2)) waveform was electronegative in 62% of group A eyes and 100% of group B eyes. The photopic 30-Hz flicker ERG was delayed in all group B eyes and all except 6 group A eyes. On-Off ERG b-waves were subnormal in 39% of group A and 89% of group B eyes; d-waves were delayed in 14 eyes (group A = 10, group B = 4). S-cone ERGs were abnormal in 50% of both groups. The PERG was abnormal in 88% of group A and 100% of group B eyes. A spoke-wheel pattern of high and low intensity was the most common FAF abnormality observed. The OCT showed intraretinal schitic cavities in the majority of eyes.

CONCLUSIONS

There is profound phenotypic variability in patients with XLRS. Most patients have DA bright-flash ERGs with a low b:a ratio in keeping with inner retinal dysfunction. Generalized cone system dysfunction is common and associated with an abnormal On-response and less frequent additional Off-response involvement. Nonsense, splice-site, or frame-shifting mutations in RS1 consistently caused electronegative bright-flash ERG, delayed flicker response, and abnormal PERG; missense mutations result in a wider range of ERG abnormalities.

Neuro-ophthalmology Annual Review

PURPOSE

To provide a clinical update of the neuro-ophthalmology literature over the last twelve months.

DESIGN

This is an annual review of current literature from August 1, 2011 to August 1, 2012.

METHODS

The authors conducted a one year English language neuro-ophthalmology literature search using PubMed from August 1, 2011 to August 1, 2012 using the following search terms: pupil abnormalities, eye movements, diseases of muscle and musculoskeletal junction, optic nerve disorders, optic neuritis and multiple sclerosis, chiasm and posterior primary visual pathway lesions, increased intracranial pressure and related entities, tumors (e.g., meningioma) and aneurysm affecting the visual pathways, vascular diseases, higher visual functions, advances in neuroimaging, and miscellaneous topics in neuro-ophthalmology. The authors included original articles, review articles, and case reports, which revealed the new aspects and updates in neuro-ophthalmology. Letters to the editor, unpublished work, and abstracts were not included in this annual literature review. We propose to update the practicing clinical ophthalmologist on the most clinically relevant literature from the past year. However, this review is not meant to be all-inclusive and highlights only the literature most applicable to the practicing clinical ophthalmologist.

RESULTS

We reviewed the literature over the past year in neuro-ophthalmology of potential interest and relevance to the comprehensive ophthalmologist.

CONCLUSION

This annual review provides a brief update on a number of neuroophthalmic conditions that might be of interest to the practicing clinical ophthalmologist.

The photopic negative response of the flash electroretinogram in multiple sclerosis

PURPOSE

To use the photopic electroretinogram (ERG) to evaluate retinal function in eyes of multiple sclerosis (MS) patients with and without a history of optic neuritis (ON) and to compare the functional and structural status of the inner retina.

METHODS

Full-field ERG responses to brief red flashes (0.04-2.8 cd · s/m²) on a rod-saturating blue background were recorded from 51 MS patients and 33 age-matched control subjects. In patients, perimetry was performed and peripapillary retinal nerve fiber layer thickness (RNFLT) was assessed by optical coherence tomography (OCT) and scanning laser polarimetry (SLP). MS eyes were separated into groups: "ON >6" months (n = 25), "ON <6" months (n = 29), and "no ON" (n = 33) based on positive or negative history of ON and time since the last episode. Thirteen ON<6 eyes were re-evaluated 1 year later.

RESULTS

PhNR amplitudes were lower in ON>6, ON<6, and no-ON eyes (mean ± SD, 17.3 ± 7.6, 16.0 ± 6.5, and 23.8 ± 9.3 μV, respectively), than in control eyes (29.8 ± 6.5 μV; P < 0.001) for a standard stimulus of 1.42 cd · s/m²; a- and b-wave amplitudes were unaffected. PhNR amplitudes correlated with visual fields mean deviation (MD) in ON>6 (r² = 0.43; P < 0.001) and no-ON eyes (r² = 0.10; P < 0.05), with similar results for weaker stimuli. PhNR amplitudes correlated with RNFLT in ON>6 eyes: OCT (r² = 0.52; P < 0.0001) and SLP (r² = 0.51; P < 0.01); and in no-ON eyes, OCT (r² = 0.21; P < 0.01) and SLP (r² = 0.17; P < 0.05). ON<6 amplitudes did not correlate significantly with other measures, but increased after 1 year by 5.1 ± 3.1 μV (P < 0.001), visual fields MD increased by 1.8 ± 2.3 dB (P < 0.05), and RNFL loss persisted.

CONCLUSIONS

Photopic ERG PhNR amplitudes in MS patients are significantly reduced in eyes with and without a history of ON.