Assessment of Macular Function by Multifocal Electroretinogram in Patients with Multiple Sclerosis Treated with Fingolimod

Effects of medications on the human electroretinogram: A comprehensive review

The electroretinogram (ERG) is a well-established method to investigate retinal function and can often provide critical diagnostic information for underlying retinal disorders. ERG responses rely on the neuronal activity of retinal cells which, like neurons elsewhere, are subject to perturbation by a wide spectrum of neuromodulating substances. These agents have the potential to confound electrophysiologic recordings used to evaluate visual function. We provide a comprehensive literature review of studies that have examined the impact of pharmacologic agents on human electrophysiologic testing of retinal function. This review is focused primarily on full-field ERG data, but also includes a limited number of studies examining effects of medications on pattern ERG and visual evoked potential recordings. The studies reviewed are categorized by medication class and evidence level according to the strength of the supporting data; for example, some included studies have a lower evidence level because they included a small number of subjects or did not use international electrophysiology testing standards. We identified numerous widely-used medications and some recreational substances that have been shown to alter ERG responses, underscoring the need to take a complete medical and medication history for each patient undergoing ERG testing.

Effect of Different Treatments on Retinal Thickness Changes in Patients With Multiple Sclerosis: A Review

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disorder affecting the central nervous system, with varying clinical manifestations such as optic neuritis, sensory disturbances, and brainstem syndromes. Disease progression is monitored through methods like MRI scans, disability scales, and optical coherence tomography (OCT), which can detect retinal thinning, even in the absence of optic neuritis. MS progression involves neurodegeneration, particularly trans-synaptic degeneration, which extends beyond the initial injury site. This review focuses on the impact of different MS treatments on retinal thickness as assessed by OCT.

RESULTS

Injectable drugs, such as interferon beta and glatiramer acetate (GA), have a relatively modest impact on retinal atrophy. Oral medications like Fingolimod, Teriflunomide, and Dimethyl fumarate also have different impacts on retinal thickness. Fingolimod has been shown to protect against retinal thinning but may lead to macular edema. DMF-treated patients had less ganglion cell-inner plexiform layer thinning than GA-treated patients but more thinning compared to natalizumab-treated patients and healthy controls. Teriflunomide's impact on retinal layers remains unexplored in human studies. Monoclonal antibodies, including Alemtuzumab, Rituximab, Ocrelizumab, and Natalizumab, had protective effects on retinal layer atrophy. Alemtuzumab-treated patients showed significantly less atrophy compared to interferon- and GA-treated patients. Rituximab initially increased atrophy rates in the first months but subsequently demonstrated potential neuroprotective effects. Ocrelizumab slowed the rate of inner nuclear layer thinning in progressive forms of the disease. Natalizumab is considered the most effective in reducing retinal layer atrophy, particularly the peripapillary retinal nerve fiber layer.

CONCLUSIONS

It's important to note that the effectiveness of these treatments may vary depending on MS subtype and individual factors. Future research should explore the long-term effects of these treatments on retinal layers and their correlations with overall disease progression and disability in MS patients.

Topographical Correlation between Structural and Functional Impairment of the Macular Inner Retinal Layers in Multiple Sclerosis Eyes with a History of Optic Neuropathy

We investigated the potential correlation between morphological and functional parameters describing the rarefaction and dysfunction of retinal ganglion cells (RGCs), located in the macula, in multiple sclerosis eyes with a history of optic neuritis (MS-ON). A total of 19 MS-ON eyes from 19 MS patients (mean age: 44.16 ± 4.66 years; 11 females and 8 males), with a mean disease duration of 10.06 ± 6.12 years and full recovery of visual acuity, and 30 age-similar (mean age: 45.09 ± 5.08 years) healthy eyes were submitted for ophthalmological evaluation using swept-source optical coherence tomography (SS-OCT) and multifocal photopic negative response (mfPhNR) to study the structural and functional features of localized RGCs. Both GCL+ thickness (via SS-OCT) and response amplitude density (RAD) (via mfPhNR) measurements were obtained from annular regions and ETDRS sectors. Morphological and electrophysiological data from the control and MS groups were compared by using an ANOVA test. GCL+ values were correlated with the corresponding RADs derived from almost superimposable areas using Pearson's tests (p < 0.01). In MS-ON eyes, the mean values of macular GCL+-T and mfPhNR RAD detected in all rings and ETDRS sectors were significantly reduced (p < 0.01) when compared with control ones. In addition, when plotting the GCL+-T and mfPhNR RAD individual data from MS-ON eyes, we found statistically significant linear correlations (p < 0.01) when considering responses from both rings and sectors. In conclusion, in MS-ON eyes, a topographical correlation between structural and functional impairment of macular RGCs occurs.

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.