Functional Evaluation of the Visual Pathway in Patients with Multiple Sclerosis Using a Multifunction Stimulator Monitor

Abstract

Objectives. To assess the capability of the vision monitor unit Monpack One of detecting visual function alterations in patients with multiple sclerosis (MS) and to evaluate the correlation between structural retinal parameters and functional measurements obtained with this device. Methods. Forty-eight patients with MS and 46 healthy controls were included in a cross-sectional study. All participants underwent a complete functional evaluation of the visual pathway, which included low-contrast visual acuity (LCVA), contrast sensitivity vision (CSV), automated perimetry, multifocal visual evoked potentials (mfVEPs), and pattern electroretinogram (ERG). All tests were performed using the vision monitor unit Monpack One (Metrovision, France), a multifunction stimulator device. Retinal structural measurements were obtained in all subjects using Triton swept source optical coherence tomography (Topcon, Japan). Results. Patients with MS presented reduced low-contrast VA (p<0.001) and reduced CSV at medium (p=0.001, p=0.013) and low (p=0.001, p=0.002) spatial frequencies. All visual field parameters were found to be altered in MS patients compared with controls (≤0.001). Patients with MS presented lower amplitude of the P100 waveform of the mfVEP in areas corresponding to central (p<0.001), inferonasal (p=0.001), and inferotemporal (p=0.003) retina. The pattern ERG did not show significant differences. Significant correlations were observed between structural retinal measurements and functional parameters, especially between the inner macular areas and measurements corresponding to contrast sensitivity and perimetry indexes. Conclusions. Patients with MS present visual dysfunction detectable with the vision monitor unit Monpack One. This device may be a fast and useful tool to provide a full evaluation of axonal damage in patients with multiple sclerosis.

Comparison of CSV-1000 and Metrovision contrast sensitivity tests in normal eyes

“…A magnocellular-based system is activated at a low spatial frequency and contrast, while in a parvocellular-based system, the opposite is true [24]. In Metrovision, the contrast and spatial frequency initially involves low-contrast gratings, which progressively increases to a higher level until the patient can detect the shape of gratings [2,14,25]. It can be postulated that the magnocellularbased system initially functions until it gradually reaches saturation, and then, with increasing contrast and spatial frequency, the parvocellular-based system takes over [24].…”

“…This interaction between screen brightness and contrast stimuli may result in higher CS scores in CSV-1000. In contrast, Metrovision uses a stimulus with an incremental contrast, and sine-wave gratings are displayed at each contrast level for a short period [2,14,25], while luminance can be set from 0.08 to 80 cd/m 2 [27]. Although a short time (5 s) was used in the CSV-1000 in the current study, to compensate for this discrepancy between the two methods, this display period was higher than the duration of the Metrovision stimuli.…”

“…Stimulus detection can be affected by adaptation and perceptual fading [28,29], which can reduce CS scores. Metrovision shows sine-wave gratings vertically, with a progressive increase in contrast from low to high, until the shape of the grating can be detected by the observer [2,14,25]. In contrast, the CSV-1000 uses stepped contrast, such that the contrast for a given frequency decreases in steps [15,30].…”

“…The CS function (CSF) curve was plotted for the right and left eyes of all participants using the Metrovision CS test. Because CS was assessed on a CSV-1000 chart for the 3, 6, 12, and 18 cpd spatial frequencies, the CS scores of these spatial frequencies were extracted from the CSF diagram provided by the Metrovision device [2,14].…”