Visual Evoked Potentials Latency Research Articles

Longitudinal effects of prenatal alcohol exposure on visual neurodevelopment over infancy.

Prenatal alcohol exposure (PAE) affects neurodevelopment in over 59 million individuals globally. Prior studies using dichotomous categorization of alcohol use and comorbid substance exposures provide limited knowledge of how prenatal alcohol specifically impacts early human neurodevelopment. In this longitudinal cohort study from Cape Town, South Africa, PAE is measured continuously-characterizing timing, dose, and drinking patterns (i.e., binge drinking). High-density electroencephalography (EEG) during a visual-evoked potential (VEP) task was collected from infants aged 8 to 52 weeks with prenatal exposure exclusively to alcohol and matched on sociodemographic factors to infants with no substance exposure in utero. First trimester alcohol exposure related to altered timing of the P1 VEP component over the first 6 months postnatally, and first trimester binge drinking exposure altered timing of the P1 VEP components such that increased exposure was associated with longer VEP latencies while increasing age was related to shorter VEP latencies (n = 108). These results suggest alcohol exposure in the first trimester may alter visual neurodevelopmental timing in early infancy. Exploratory individual-difference analysis across infants with and without PAE tested the relation between VEP latencies and myelination for a subsample of infants with usable magnetic resonance imaging (MRI) T1w and T2w scans collected at the same time point as EEG (n = 47). Decreased MRI T1w/T2w ratios (an indicator of myelin) in the primary visual cortex (n = 47) were linked to longer P1 VEP latencies. Results from these two sets of analyses suggest that prenatal alcohol and postnatal myelination may both separately impact VEP latency over infancy. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Bexarotene leads to durable improvements in visual evoked potential latency: A follow-up study of the Cambridge Centre for Myelin Repair One trial.

The Cambridge Centre for Myelin Repair One (CCMR-One) trial showed that 6 months of bexarotene reduces visual evoked potential (VEP) latency in people with relapsing-remitting multiple sclerosis (MS). In a single-centre follow-up study of these participants, we re-examined full-field VEP and clinical assessments. Twenty participants (12 bexarotene and 8 placebo) were seen on average 27 months after their trial involvement. In an analysis of all eyes with recordable signal (24 bexarotene and 14 placebo), the adjusted bexarotene-placebo treatment difference in P100 latency was -7.79 (95% confidence interval (CI) = -14.76, -0.82) ms, p = 0.044. We conclude that there were durable improvements in VEP latency, suggesting long-term benefits from exposure to a remyelinating drug.

Knocking out the LRRK2 gene increases sensitivity to wavelength information in rats

Leucine-rich repeat kinase 2 (LRRK2) is a gene related to familial Parkinson’s disease (PD). It has been associated with nonmotor symptoms such as disturbances in the visual system affecting colour discrimination and contrast sensitivity. This study examined how deficiency of LRRK2 impacts visual processing in adult rats. Additionally, we investigated whether these changes can be modelled in wild-type rats by administering the LRRK2 inhibitor PFE360. Visual evoked potentials (VEPs) and steady-state visual evoked potentials (SSVEPs) were recorded in the visual cortex and superior colliculus of female LRRK2-knockout and wild-type rats to study how the innate absence of LRRK2 changes visual processing. Exposing the animals to stimulation at five different wavelengths revealed an interaction between genotype and the response to stimulation at different wavelengths. Differences in VEP amplitudes and latencies were robust and barely impacted by the presence of the LRRK2 inhibitor PFE360, suggesting a developmental effect. Taken together, these results indicate that alterations in visual processing were related to developmental deficiency of LRRK2 and not acute deficiency of LRRK2, indicating a role of LRRK2 in the functional development of the visual system and synaptic transmission.

Investigation of optic nerve function in Behçet's patients with optic disc hyperfluorescence in fundus fluorescein angiography.

The aim was to investigate the changes in optic nerve function that may help in the diagnosis of subclinical optic nerve involvement in patients with Behçet's disease (BD) and isolated optic disc (OD) hyperfluorescence in fluorescein angiography (FA). Three groups were formed; BD patients with isolated OD hyperfluorescence in FA, BD patients without ocular involvement (normal FA) and control group. A total of 88 eyes of 45 patients were included. The groups were compared in terms of OCT-RNFL, contrast sensitivity and VEP latency. When the OCT-RNFL values were compared, there was a significant difference between the control group and Behçet's patients with normal FA. Contrast sensitivity values differed significantly among the groups, and the lowest mean contrast sensitivity was observed in the group with OD hyperfluorescence (p < 0.05). As far as we know, this is the first publication that investigates optic nerve function in BD patients with isolated OD hyperfluorescence in FA. Assessment with FA of asymptomatic BD patients with visual complaints and low contrast sensitivity may be helpful at early detection of inflammatory optic neuropathy by close follow-up in patients with OD hyperfluorescence.

The Effect of Ethambutol Therapy in terms of Visual Evoked Potential, Color Vision Test, and Contrast Sensitivity Test at the Subclinical Level

Abstract&#x0D; Introduction &amp; Objectives : Ethambutol is one of the first-line drugs in the treatment of tuberculosis and known to induce optic neuropathy. However, there are unknown protocols for detecting subclinical level of toxicity. The aim of this study was to assess the difference in amplitude and latency of visual evoked potential (VEP), color vision, and contrast sensitivity in tuberculosis patients before and after taking ethambutol for 1 and 2 months.&#x0D; Methods : This was a prospective observational cohort study of 38 eyes of 19 newly diagnosed patients with category-1 tuberculosis being treated with ethambutol. All patients were given ethambutol for 2 months at a dose of 15 - 20 mg/kg body weight/day. The participants underwent complete eye and visual function examination including pattern-reversal VEP, color vision with Farnsworth Munsell D-15 test, and contrast sensitivity with LEA Low Contrast Flip Chart before and after 1 and 2 months of treatment. Wilcoxon test was employed for data analysis.&#x0D; Results : During the study, no changes in visual acuity was observed. The results showed that the latencies of VEP after 1 month (p = 0.000) and 2 months (p = 0.000) of treatment were significantly delayed. There was a significant difference in contrast sensitivity after 2 months (p = 0.014) of treatment. However, no significant difference was found in color vision and amplitude of VEP.&#x0D; Conclusion : Latency of VEP and contrast sensitivity test could prove useful in detecting subclinical and hence very useful for monitoring patients under ethambutol therapy for ocular toxicity.

Evoked potentials after autologous hematopoietic stem cell transplantation for multiple sclerosis

ObjectiveTo investigate the effect of autologous hematopoietic stem cell transplantation (AHSCT) on functional aspects of the nervous system assessed by visual (VEP), somatosensory (SEP), and motor (MEP) evoked potentials in patients with relapsing-remitting multiple sclerosis. BackgroundSeveral studies have demonstrated the efficacy of AHSCT on inflammatory activity and disability progression in patients with multiple sclerosis. However, the impact of AHSCT on evoked potentials has not been evaluated before. MethodsTwelve AHSCT-treated patients from Uppsala University Hospital were consecutively recruited. Evoked potentials (EP) were collected at baseline and two follow-up visits, 3 and 12 months post-AHSCT. We calculated a composite EP score for each participant and compared it between different time points. ResultsThe median total EP score decreased from 5 at baseline, to 2.5 at 12 months post-ASHCT (p = 0.008). A significant improvement in tibial SEP (tSEP) latencies was observed (42.7 vs 41.5 ms, p < 0.001), with a similar trend for MEP latencies 12 months post-ASHCT. No significant changes in median SEP or VEP latencies were observed. ConclusionsTreatment with AHSCT was associated with improved transmission in some central nervous system pathways in multiple sclerosis patients.

Combination among VEP, OCT and TCD data in patients with relapsing-remitting multiple sclerosis during attack-free period

Aims Multiple sclerosis (MS) is characterized by inflammation, demyelination, glial cell pathology and axonal injury in the central nervous system, and also progressive axonal loss of the optic nerve in cases with optic neuritis (ON). The previous transcranial Doppler (TCD) investigations suggest cortical hyperreactivity in patients with relapsing-remitting Multiple sclerosis (RRMS). We investigated the effect of ON involvement on visual reactivity. Material and methods One hundred thirty patients with RRMS during attack-free period and 12 healthy subjects were enrolled to the study. Visual evoked potential (VEP), optic coherence tomography (OCT) and TCD examinations of all subjects were performed. Results Cerebrovascular reactivity measured with breath holding (BH) test was found to be normal. VEP amplitude, visual reactivity and peripapillary retinal nerve fibre layer (pRNFL) measurements were found to be low in patients with ON involvement, whereas VEP latencies were long. Visual reactivity was negatively correlated with VEP amplitude and RFNL measurements, and positively correlated with VEP latency. Conclusions The present study supports that cerebrovascular reactivity is preserved in patients with RRMS except for attacks, and neurovascular reactivity is increased in patients without ON involvement.

Simultaneous Dry and Gel-Based High-Density Electroencephalography Recordings.

Evaluations of new dry, high-density EEG caps have only been performed so far with serial measurements and not with simultaneous (parallel) measurements. For a first comparison of gel-based and dry electrode performance in simultaneous high-density EEG measurements, we developed a new EEG cap comprising 64 gel-based and 64 dry electrodes and performed simultaneous measurements on ten volunteers. We analyzed electrode-skin impedances, resting state EEG, triggered eye blinks, and visual evoked potentials (VEPs). To overcome the issue of different electrode positions in the comparison of simultaneous measurements, we performed spatial frequency analysis of the simultaneously measured EEGs using spatial harmonic analysis (SPHARA). The impedances were 516 ± 429 kOhm (mean ± std) for the dry electrodes and 14 ± 8 kOhm for the gel-based electrodes. For the dry EEG electrodes, we obtained a channel reliability of 77%. We observed no differences between dry and gel-based recordings for the alpha peak frequency and the alpha power amplitude, as well as for the VEP peak amplitudes and latencies. For the VEP, the RMSD and the correlation coefficient between the gel-based and dry recordings were 1.7 ± 0.7 μV and 0.97 ± 0.03, respectively. We observed no differences in the cumulative power distributions of the spatial frequency components for the N75 and P100 VEP peaks. The differences for the N145 VEP peak were attributed to the different noise characteristics of gel-based and dry recordings. In conclusion, we provide evidence for the equivalence of simultaneous dry and gel-based high-density EEG measurements.

Exaggerated response to pattern reversal visual evoked potential among migraineurs

Objective Visual evoked potential recording has reported ambiguous results among migraineurs, thus the present study explored the association of check-size and reversal rates on the latency and amplitude of pattern reversal VEP among migraineurs. Method and material Monocular VEP responses for both eyes were recorded in 133 migraineurs and 111 controls. Checkerboard pattern with phase reversal frequency of 0.5, 1, 2 and 4 Hz and check-size of 16 × 16, 32 × 32, 64 × 64 and 128 × 128, i.e. spatial frequency of 0.475, 1.029, 2.056 and 4.112 cycle per degree (cpd) were used to record 100 responses each. Three-minutes gap was given after change of reversal frequency to a higher rate for next cycle of 4 check-size records. Result A linear increase in latencies was observed with decreasing check-size in both groups, but migraineurs had significantly higher latencies at a given reversal rate. Amplitudes A1 and A2 were higher among migraineurs and amplitude A2 showed an inverted ‘U’ shaped trend with maximum amplitude at 32 × 32 check size (1.029 cpd) in both groups, with an exaggerated response among migraineurs. Check-size 32 × 32 i.e. spatial frequency of 1.029 behaves differently than other larger or smaller check-sizes. Conclusion Variable VEP response for different visual stimuli may be due to differential activation of respective retinocortical pathways and cortical areas. The highest amplitude at modest check-size suggests a contributory role of foveal-parafoveal fibres in migraineurs. Exaggerated physiological response to visual stimuli may be responsible for higher amplitudes and prolonged latencies among migraineurs.

The effect of different blood groups on visual evoked potentials

Introduction and aim. Purpose of the study is to determine whether it is required to use different standards when evaluating visual evoked potential (VEP) measurements of healthy individuals with different blood groups. Material and methods. The study consisted of healthy individuals with different blood groups who have applied to the ophthalmology and neurology outpatient clinic of Düzce University Medical Faculty from January to December 2022. The patients went through detailed ophthalmologic examination and VEP test and only the ones with normal results were included to the study. Results. The study consisted of 119 individuals, with a blood group distribution of 30 A, 29 B, 30 AB and 30 O. VEP latency and amplitude changes were compared and no significant difference was observed within 4 groups in terms of P100 and N70 latency and amplitudes. There was N70 latency prolongation in Rh- group and this difference was found to be statistically significant (p=0.009). Rh+ group was found to be high in terms of P100 amplitudes and this was considered statistically significant (both p=0.023). Conclusion. There was no statistically significant difference in the VEP parameters of the individuals with the ABO blood groups hence same VEP normal values can be used for ABO blood groups.

Electrophysiological and Histological Correlations of Optic Neuritis in the Dark Agouti Rat Model of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of Inflammatory central nervous system (CNS) disease. Dark agouti (DA) rats immunized with full-length myelin oligodendrocyte glycoprotein (MOG1-125) typically develop a relapsing-remitting EAE form characterized by predominant demyelinating involvement of the spinal cord and optic nerve. Visually evoked potentials (VEP) are a useful objective tool to assess the optic nerve function and monitor electrophysiological changes in optic neuritis (ON). The current study aimed to assess the VEP changes in MOG-EAE DA rats using a minimally invasive recording device and to correlate them with histological findings. Twelve MOG-EAE DA rats and four controls underwent VEP recording at day 0, 7, 14, 21, and 28 post-EAE induction. Tissue samples were obtained on days 14, 21, and 28 from two EAE rats and one control. The median VEP latencies were significantly higher on days 14, 21, and 28 compared to baseline, with maximal latencies observed on day 21. The histological analyses on day 14 demonstrated inflammation with largely preserved myelin and axonal structures. Inflammation and demyelination with largely preserved axons were evident on days 21 and 28, which correlated with prolonged VEP latencies. These findings suggest that VEPs may be a reliable biomarker reflecting the optic nerve involvement in EAE. Moreover, the use of a minimally invasive device enables observation of VEP changes over time in MOG-EAE DA rats. Our findings may have important implications for testing the potential neuroprotective and regenerative effects of new therapies for CNS demyelinating diseases.

Effects of Smoking on Pattern Visual Evoked Potentials

Aim: The aim of the study is to get a better understanding of the side effects of smoking by evaluating the effect of recently elevated smoking rate on Visual Evoked Potentials (VEP) and to determine whether it is necessary to use different normals when evaluating the VEP measurements of smoking patients. Material and Methods: The patients who have applied to our ophthalmology and neurology outpatient clinics during 2021-2022 are included to the study. Detailed ophthalmologic examination of the patients as well as their VEP test is completed followed by a dilated fundus examination assessment. The patients with normal results are included to the study. The smoking rate is calculated on pack/year basis. Pattern VEP (PVEP) recording is performed based on Keypoint (Dantec, Denmark) and International Society for Clinical Electrophysiology of Vision (ISCEV) criteria. Data obtained through the study are analyzed by SPSS 21.0 version software. Countable variables with normal distribution between two independent groups are analyzed with Independent Sample T test whereas variables without normal distribution are analyzed with Mann Whitney U test. Chi-square test is used for comparing categorical variables. Results: 71 patients were included to the study where 33 of them were placed in smoking group and 38 in non-smoking group (control group). Smoking group had a yearly cigarette package consumption of 5.20±8.93 (0.2-40). VEP latency and amplitude changes were compared and according to the obtained results; there was P100 latency prolongation in between left and right eye of the patients in the control group and smoking group but it did not have any statistical significance (p=0.910 and p=0.697 respectively). There was no statistically significant difference in either left nor right eye in terms of smoking and P100 and N70 latencies (p=0.707, p=0.838, p=0.717 and p=0.621 respectively). Similarly, there was no significant correlation between yearly package consumption and P100 and N70 latencies and amplitudes of left and right eyes (p=0.503, p=0.410, p=0.776 and p=0.940 respectively). Conclusion: No significant effect of smoking is found on VEP values thus leading us to believe that the same normal intervals can be used in the evaluation of VEP results of both smoking and non-smoking patients.

MWF of the corpus callosum is a robust measure of remyelination: Results from the ReBUILD trial

Myelin repair is an unrealized therapeutic goal in the treatment of multiple sclerosis (MS). Uncertainty remains about the optimal techniques for assessing therapeutic efficacy and imaging biomarkers are required to measure and corroborate myelin restoration. We analyzed myelin water fraction imaging from ReBUILD, a double-blind, randomized placebo-controlled (delayed treatment) remyelination trial, that showed a significant reduction in VEP latency in patients with MS. We focused on brain regions rich in myelin. Fifty MS subjects in two arms underwent 3T MRI at baseline and months 3 and 5. Half of the cohort was randomly assigned to receive treatment from baseline through 3mo, whereas the other half received treatment from 3mo to 5mo post-baseline. We computed myelin water fraction changes occurring in normal-appearing white matter of corpus callosum, optic radiations, and corticospinal tracts. An increase in myelin water fraction was documented in the normal-appearing white matter of the corpus callosum, in correspondence with the administration of the remyelinating treatment clemastine. This study provides direct, biologically validated imaging-based evidence of medically induced myelin repair. Moreover, our work strongly suggests that significant myelin repair occurs outside of lesions. We therefore propose myelin water fraction within the normal-appearing white matter of the corpus callosum as a biomarker for clinical trials looking at remyelination.

Amplitude and latency of visual evoked potential are un-correlated variables: A revelation from normative laboratory database of eastern India

To establish normative database andinvestigate whether VEP amplitude and latency have any correlation between them. Institution based cross-sectional observational study done in Electrophysiology of Vision Laboratory at a tertiary centre in Eastern India. 126 subjects of age group between 20 and 59 years of either sex with best corrected visual acuity 6/6 in both eyes and no other eye ailments (except error of refraction) on examination with informed consent were included. PVEP with pattern reversal stimulus with check element size 1° (60') was recorded with Retimax “Advanced” machine (manufactured by CSO s.r.l., (Firenze) Italy) and standard silver-silver chloride disc electrodes. The test parameters were customized in the machine by the manufacturer and designated to measure the N75-P100 amplitude and P100 latency.Normative values were established for our laboratory. Only the most reliable parameters for clinically significant alterations of visual pathway i.e. N75-P100 amplitude and P100 latency were included in the analysis. Results of uniocular, age group-wise and gender-wise values were obtained by descriptive statistics as per ISCEV guidelines. No linear co-relationship (ascertained by Spearman's rho Correlation Coefficient) was found between N75-P100 amplitude and P100 latency, in either of the eyes. PVEP amplitude and latency are uncorrelated variables. To the best of our knowledge, our study was the first study in literature on correlation between amplitude and latency of PVEP.

Visually Evoked Potential as Prognostic Biomarker for Neuroaxonal Damage in Multiple Sclerosis From a Multicenter Longitudinal Cohort.

With the increasing use of visually evoked potentials (VEPs) as quantitative outcome parameters for myelin in clinical trials, an in-depth understanding of longitudinal VEP latency changes and their prognostic potential for subsequent neuronal loss will be required. In this longitudinal multicenter study, we evaluated the association and prognostic potential of VEP latency for retinal neurodegeneration, measured by optical coherence tomography (OCT), in relapsing-remitting MS (RRMS). We included 293 eyes of 147 patients with RRMS (age [years, median ± SD] 36 ± 10, male sex 35%, F/U [years, median {IQR} 2.1 {1.5-3.9}]): 41 eyes had a history of optic neuritis (ON) ≥6 months before baseline (CHRONIC-ON), and 252 eyes had no history of ON (CHRONIC-NON). P100 latency (VEP), macular combined ganglion cell and inner plexiform layer volume (GCIPL), and peripapillary retinal nerve fiber layer thickness (pRNFL) (OCT) were quantified. P100 latency change over the first year predicted subsequent GCIPL loss (36 months) across the entire chronic cohort (p = 0.001) and in (and driven by) the CHRONIC-NON subset (p = 0.019) but not in the CHRONIC-ON subset (p = 0.680). P100 latency and pRNFL were correlated at baseline (CHRONIC-NON p = 0.004, CHRONIC-ON p < 0.001), but change in P100 latency and pRNFL were not correlated. P100 latency did not differ longitudinally between protocols or centers. VEP in non-ON eyes seems to be a promising marker of demyelination in RRMS and of potential prognostic value for subsequent retinal ganglion cell loss. This study also provides evidence that VEP may be a useful and reliable biomarker for multicenter studies.

Retinal sensitivity and gaze fixation evaluated by microperimetry in subjects with type 2 diabetes: two independent parameters that explore different neuronal circuits

Background and aimsRetinal sensitivity (RS) and gaze fixation (GF) assessed by retinal microperimetry are useful and complementary tools for identifying mild cognitive impairment (MCI) in patients with type 2 diabetes (T2D). The hypothesis is that RS and GF examine different neural circuits: RS depends only on the visual pathway while GF reflects white matter complex connectivity networks. The aim of the study is to shed light to this issue by examining the relationship of these two parameters with visual evoked potentials (VEP), the current gold standard to examine the visual pathway.Materials and methodsConsecutive T2D patients > 65 years were recruited from the outpatient clinic. Retinal microperimetry (MAIA 3rd generation) and visual evoked potentials (VEP) (Nicolet Viking ED). RS (dB), GF (BCEA63%, BCEA95%) (MAIA) and VEP (Latency P100ms, Amplitude75–100 uV) were analyzed.ResultsThirty three patients (45% women, 72.1 ± 4.6 years) were included. VEP parameters significantly correlated with RS but not with GF.ConclusionsThese results confirm that RS but not GF depends on the visual pathway, reinforcing the concept that they are complementary diagnostic tools. Used together can further increase the value of microperimetry as screening test for identifying T2D population with cognitive impairment.

Visually evoked potentials (VEPs) across the visual field in hearing and deaf cats.

Congenitally deaf cats perform better on visual localization tasks than hearing cats, and this advantage has been attributed to the posterior auditory field. Successful visual localization requires both visual processing of the target and timely generation of an action to approach the target. Activation of auditory cortex in deaf subjects during visual localization in the peripheral visual field can occur either via bottom-up stimulus-driven and/or top-down goal-directed pathways. In this study, we recorded visually evoked potentials (VEPs) in response to a reversing checkerboard stimulus presented in the hemifield contralateral to the recorded hemisphere in both hearing and deaf cats under light anesthesia. Although VEP amplitudes and latencies were systematically modulated by stimulus eccentricity, we found little evidence of changes in VEP in deaf cats that can explain their behavioral advantage. A statistical trend was observed, showing larger peak amplitudes and shorter peak latencies in deaf subjects for stimuli in the near- and mid-peripheral field. Additionally, latency of the P1 wave component had a larger inter-sweep variation in deaf subjects. Our results suggested that cross-modal plasticity following deafness does not play a major part in cortical processing of the peripheral visual field when the "vision for action" system is not recruited.

Function Evaluation of Diabetic Vitreous Hemorrhage After Vitrectomy

Purpose: The aim of this study is to evaluate electrophysiological changes before and after pars plana vitrectomy for diabetic vitreous hemorrhage Subject &amp; Method: This study included 30 eyes of 30 patients with diabetic vitreous hemorrhage undergoing pars plana vitrectomy. All subjects underwent complete ophthalmological examination, Ultrasonography, Visual evoked potential, Electroretinography before and after vitrectomy (at 1 week &amp;3 months) Results: There was a statistically significant improvement in the Uncorrected Visual Acuity (UCVA) and the Best Corrected Visual Acuity (BCVA) along the study period (p &lt;0.001). There was statistically significant improvement in the mean latency and mean amplitude of Flash VEP There was a statistically significant increase in the mean amplitude of all ERG parameters at 3 months postoperative. Conclusion: Electrophysiological test is an important tool in detection improvement of retinal function after vitrectomy

The Relationship between Visual-Evoked Potential and Optic Coherence Tomography and Clinical Findings in Parkinson Patients.

In Parkinson's disease (PD), dopamine deficiency is present not only in the nigrostriatal pathway but also in the retinal and visual pathways. Optic coherence tomography (OCT) can be used as morphological evidence of visual influence from early nonmotor symptoms. The aim of this study was to investigate the relationship of OCT and visual evoked potentials (VEPs) of eyes with the severity of clinical findings and ocular findings in PD. A group of 42 patients diagnosed with idiopathic PD and a control group of 29 people between the ages of 45-85 were included in our study. VEP was recorded in the patient and control groups. OCT measurement was made with the Optovue spectral-domain device. Foveal thickness and macular volume were measured in the foveal region and in the parafoveal and perifoveal regions in the temporal, superior, nasal, and inferior quadrants. RNFL (retinal nerve fiber layer) was measured in temporal, superior, nasal, and inferior quadrants. Ganglion cell complex (GCC) was evaluated in the superior and inferior quadrants. Using the UPDRS clinical scale, the relationship between measurements and the differences between the control group and the patient group were evaluated. Among the OCT values in our study, foveal, parafoveal, perifoveal thickness, macular volume, RNFL, and GCC measurements were performed for the right and left eyes, and no difference was found between the patient group and the control group. There was no difference in VEP amplitude and latency values between the patient and control groups. The relationships between UPDRS and modified Hoehn Yahr staging and OCT and VEP measurements in the patient revealed no correlation. Studies on whether OCT measurements can functionally be a marker or which segments are more valuable for disease progression in patients with PD are needed. Visual dysfunction in PD cannot be attributed only to retinal pathology; however, the retina may provide monitoring of the status of dopaminergic neurodegeneration and axonal loss in PD.

Evaluation of Diurnal Changes of Mental Fatigue Using a New Portable Device for Visual Cognitive Evoked Potentials.

In the age homogenous group of 13 healthy volunteers, we examined visual evoked potentials (VEP) visually evoked cognitive potentials (event-related potentials - ERP) and choice reaction time (CRT) five times during the day (from 10.00 a.m. up to midnight) to verify whether there are significant changes of the measured parameters of the cortical evoked potentials and CRT which might reflect the level of the mental fatigue. The electrophysiological testing was done with the use of a new portable VEP device named "VEPpeak" enabling to perform the examination outside standard labs in almost any conditions. It was found that the latency of ERP (P300 peak time) and CRT displayed significant prolongation toward midnight while VEP latency and all amplitudes did not change significantly. This pilot study supports our idea that the portable VEP device possibly might be used for the objective examination of mental fatigue that is needed in many situations. This should be confirmed in a larger study also including a comparison with non-electrophysiological fatigue testing.