Visual Evoked Potentials Examination Research Articles

Optic nerve involvement in patients with Lyme neuroborreliosis: an electrophysiological study.

The aim of this neurophysiological study was to retrospectively analyze visual evoked potentials (VEPs) acquired during an examination for diagnosing optic nerve involvement in patients with Lyme neuroborreliosis (LNB). Attention was focused on LNB patients with peripheral facial palsy (PFP) and optic nerve involvement. A total of 241 Czech patients were classified as having probable/definite LNB (193/48); of these, 57 were younger than 40 years, with a median age of 26.3 years, and 184 were older than 40 years, with a median age of 58.8 years. All patients underwent pattern-reversal (PVEP) and motion-onset (MVEP) VEP examinations. Abnormal VEP results were observed in 150/241 patients and were noted more often in patients over 40 years (p = 0.008). Muscle/joint problems and paresthesia were observed to be significantly more common in patients older than 40 years (p = 0.002, p = 0.030), in contrast to headache and decreased visual acuity, which were seen more often in patients younger than 40 years (p = 0.001, p = 0.033). Peripheral facial palsy was diagnosed in 26/241 LNB patients. Among patients with PFP, VEP peak times above the laboratory limit was observed in 22 (84.6%) individuals. Monitoring of patients with PFP and pathological VEP showed that the adjustment of visual system function occurred in half of the patients in one to more years, in contrast to faster recovery from peripheral facial palsy within months in most patients. In LNB patients, VEP helps to increase sensitivity of an early diagnostic process.

Clinical features of 6 children with uridine-responsive developmental epileptic encephalopathy 50 caused by CAD gene variants

Objective: To analyze the clinical features of children with uridine responsive developmental epileptic encephalopathy 50 (DEE50) caused by CAD gene variants. Methods: A retrospective study was conducted on 6 patients diagnosed with uridine-responsive DEE50 caused by CAD gene variants at Beijing Children's Hospital and Peking University First Hospital from 2018 to 2022. The epileptic seizures, anemia, peripheral blood smear, cranial magnetic resonance imaging (MRI), visual evoked potential (VEP), genotype features and the therapeutic effect of uridine were descriptively analyzed. Results: A total of 6 patients, including 3 boys and 3 girls, aged 3.5(3.2,5.8) years, were enrolled in this study. All patients presented with refractory epilepsy, anemia with anisopoikilocytosis and global developmental delay with regression. The age of epilepsy onset was 8.5 (7.5, 11.0) months, and focal seizures were the most common seizure type (6 cases). Anemia ranged from mild to severe. Four patients had peripheral blood smears prior to uridine administration, showing erythrocytes of variable size and abnormal morphology, and normalized at 6 (2, 8) months after uridine supplementation. Two patients suffered from strabismus, 3 patients had VEP examinations, indicating of suspicious optic nerve involvement, and normal fundus examinations. VEP was re-examined at 1 and 3 months after uridine supplementation, suggesting significant improvement or normalization. Cranial MRI were performed at 5 patients, demonstrating cerebral and cerebellar atrophy. They had cranial MRI re-examined after uridine treatment with a duration of 1.1 (1.0, 1.8) years, indicating significant improvement in brain atrophy. All patients received uridine orally at a dose of 100 mg/(kg·d), the age at initiation of uridine treatment was 1.0 (0.8, 2.5) years, and the duration of treatment was 2.4 (2.2, 3.0) years. Immediate cession of seizures was observed within days to a week after uridine supplementation. Four patients received uridine monotherapy and were seizure free for 7 months, 2.4 years, 2.4 years and 3.0 years respectively. One patient achieved seizure free for 3.0 years after uridine supplementation and had discontinued uridine for 1.5 years. Two patients were supplemented with uridine combined with 1 to 2 anti-seizure medications and had a reduced seizure frequency of 1 to 3 times per year, and they had achieved seizure free for 8 months and 1.4 years respectively. Conclusions: The clinical manifestations of DEE50 caused by CAD gene variants present a triad of refractory epilepsy, anemia with anisopoikilocytosis, and psychomotor retardation with regression, accompanied by suspected optic nerve involvement, all of which respond to uridine treatment. Prompt diagnosis and immediate uridine supplementation could lead to significant clinical improvement.

VEP examination with new portable device

IntroductionWe developed a new portable device called “VEPpeak” for the examination of visual evoked potentials (VEPs) to extend VEP examination beyond specialized electrophysiological laboratories and to simplify the use of this objective, noninvasive, and low-cost method for diagnostics of visual and central nervous system dysfunctions.MethodsVEPpeak consists of a plastic headset with a total weight of 390 g containing four EEG amplifiers, an A/D converter, a control unit, and a visual LED stimulator built in the front, vertically adjustable peak. The device is powered and controlled via USB connection from a standard PC/notebook using custom software for visual stimuli generation and for VEP recording and processing. Up to four electrodes can be placed at any scalp location or in combination with two dry electrodes incorporated into the headset. External visual stimulators, such as a tablet, can be used with synchronization. Feasibility and validation studies were conducted with 86 healthy subjects and 76 neuro-ophthalmological patients including 67 who were during the same session also tested with a conventional VEP system.ResultsVEPpeak recordings to standard (pattern-reversal) and non-standard (motion-onset, red-green alternation) were robust and repeatable and obtained also in immobilized patients. Good comparability of results was achieved between VEPpeak and standard examination. Some systematic differences in peak latencies and amplitudes are consistent with differences in stimulus characteristics of the two compared systems.DiscussionVEPpeak provides an inexpensive system for clinical use requiring portability. In addition to ISCEV standard VEP protocols, free choice of stimuli and bio-signal recordings make the device universal for many electrophysiological purposes.

OCT and VEP correlate to disability in secondary progressive multiple sclerosis

BackgroundThe afferent visual pathway provides a unique opportunity to monitor clinical and subclinical optic neuritis and features of neuroaxonal degeneration in secondary progressive MS. ObjectiveTo investigate the usefulness of visual evoked potentials (VEP) and optical coherence tomography (OCT) in evaluating SPMS, and the association between these modalities and clinical course and lesion load on the magnetic resonance imaging (MRI) in patients with SPMS with or without a history of optic neuritis (ON). MethodsSPMS patients (n = 27) underwent clinical assessment with Expanded Disability Status Scale (EDSS) grading, visual acuity, OCT, and VEP examination. MRI of the brain and spinal cord were evaluated. Ordinal scores of VEP and MRI findings were used in the statistical analyses. ResultsThe ganglion cell and inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) thickness correlated with VEP latency. VEP P100 score correlated with EDSS. Linear regression showed an association between GCIPL thickness and EDSS as well as VEP P100 latency and EDSS. The MRI analyses were negative. ConclusionVEP latency and GCIPL thickness correlated with disability measured as EDSS in patients with SPMS and are useful in monitoring SPMS patients.

Role of high dose intravenous methylprednisolone and visual evoked potential (VEP) in the management of methyl alcohol poisoning: A case series report

To study the effectiveness of high dose intravenous methylprednisolone and to discuss the role of visual evoked potential (VEP) as a marker of severity and of improvement in methyl alcohol poisoning.In an outbreak of methanol poisoning, a total of six patients presented to JNMCH, AMU. Meticulous history was taken followed by examination. They were treated with high dose IV methyl prednisolone and later underwent visual evoked potential testing. The patients were examined daily till the time of discharge and then followed up at 1 month.Following treatment with high dose IV methyl prednisolone, 100% of cases showed improvement in vision which was judged on the basis of visual acuity and visual evoked potential assessment at the time of presentation. As recorded by VEP, 4 patients (66.6%) had prolonged P100 latency while no response was recorded in 2 patients (33.3%). In 3 (50%) of the 6 cases, improvement in visual acuity of at least two lines of Snellen chart was observed at 1 month follow-up while two patients (33.3%) improved from doubtful light perception to counting fingers at least 2 metres and one patient (16.6%) improved from perception of light present to counting finger at least 2 metres.Early presentation and timely intervention improves visual outcome in methanol poisoning. High-dose IV methylprednisolone seems to have benefits in the treatment of methanol optic neuropathy. The VEP examination appears to be a sensitive marker for diagnosis and prognosis of even subclinical impairment of the optic system due to methanol poisoning.

Serial cases: visual evoked potentials (VEP) in demyelinating disease

Optic neuritis (NO) is an acute inflammatory demyelinating disease of the optic nerve. The optic nerve's demyelination is the most common symptom found in Multiple Sclerosis (MS) and Neuromyelitis Optica (NMO). Visual Evoked Potentials (VEP) can provide additional information regarding the integrity of the anterior visual pathway from the retina to the visual cortex. Until now, VEP examination is still rarely performed, so further research is needed on the characteristics of demyelinating disease with optic neuritis.

Normative values of visual evoked potential in adults.

Purpose:Visual evoked potentials (VEP) are used to determine the function of visual pathway from the optic nerve to visual cortex. Various factors may affect VEP response, viz., technical and environmental. The aim of this study is to obtain the normative value of VEP latency and amplitude parameters in adulthood in Indonesia, as well as the relationship of height, weight, body mass index (BMI), head circumference, and visual acuity with the variety of latency and amplitude values of VEP parameters.Methods:It is a cross-sectional study on 120 healthy subjects consisting of 60 males and 60 females between 18 and 65 years old. Height, weight, BMI, head circumference, and visual acuity were measured and continued with VEP examination using a 26′ checkerboard pattern on the left and right eyes alternately. All data were collected and analyzed with the Shapiro–Wilk test using statistical software R version 3.5.2.Results:Mean value of P100 latency (interocular latency) of left and right eye were 104.6 ± 3.4 ms and 104.1 ± 3.4 ms, respectively, as well as 9.8 ± 4.7 μV and 10.3 ± 5.4 μV for the amplitude. There was no significant difference between the male and female group, as well as on the age group. Female significantly exhibited a higher P100 amplitude than male. The greater the age, the lower amplitude of P100 significantly.Conclusion:Gender and age do not affect the P100 latency value but only affect P100 amplitude. Height, weight, BMI, head circumference, and visual acuity also do not affect the P100 latency and amplitude.

Need for Visual Pathway Examination of the Patient Prior to Bone Marrow Transplantation

Aim: Bone Marrow Transplantation is a treatment procedure usually applied for the patients suffering from leukemia. It is observed that some of these patients complain from partial vision loss few months after the operation whereas the routine visual examination of these patients are normal, therefore the aim of present work is to examine the visual pathway of these patients to search for the probable visual pathway degeneration of these patients using visual evoked potential (VEP). Method: 10 patients following bone marrow transplantation were selected randomly. These patients had this operation for at least one year before. Routine ophthalmological examination of them was normal or at most they had refractive error problem which could be corrected by suitable spectacles. Visual evoked potential was recorded in these patients. Latency (msec) and amplitude (μv) of VEP, P100 Peak was noted for each patient. Beside these patients, 10 people with healthy visual system were selected to compare the result of VEP in patients with healthy group following VEP recording. Result: It is observed that 4 patients had abnormal VEP pattern which was reflected either in latency or amplitude of VEP, P100 Peak. Conclusion: From the result of present work, one can conclude that VEP examination of patients following bone marrow transplantation is necessary prior to operation so that if any unexplained visual loss is observed after operation, the medical staff can follow the case for the probable reason for this malfunction.

Study on the variation of visual evoked potential and its diagnostic value in children with optic neuritis

Objective To investigate the characteristics and clinical value of visual evoked potentials(VEP) in children with optic neuritis. Methods The VEP of 33 children with optic neuritis were tested by NICOLET evoked potential instrument.The results were compared with those of cranial and/or orbital MRI and fundus examination, and the consistency with visual performance was analyzed.The correlation between visual sensitivity and VEP results was analyzed. Results Among 33 children with optic neuritis, the abnormal rate of VEP in 52 abnormal eyes was 88.5%; the abnormal rate of cranial and/or orbital MRI was 38.5%; the abnormal rate of fundus examination was 62.2%; the abnormal rate of VEP examination was significantly higher than that of cranial and/or orbital MRI and fundus examination (P<0.05); the consistency rate between VEP examination and visual acuity was 84.8%.The consistency rate between pattern reversal visual evoked potential (P-VEP) and visual acuity was 86.8%, and that between flash visual evoked potential (F-VEP) and visual acuity was 82.1%.With the increase of visual impairment, the percentage of P100 wave loss increased gradually.There was no correlation between visual acuity and the prolongation of P100 wave latency. Conclusion There are significant differences between VEP and fundus examination and MRI, the sensitivity of VEP is superior to both.P-VEP is more consistent with visual acuity than F-VEP.VEP has certain value in evaluating the degree of visual impairment in children with optic neuritis.It can not be used to evaluate the level of optic sensitivity when the latency of P100 wave is prolonging. Key words: Optic neuritis; Visual evoked potentials; Visual; Children

Atypical Optic Nerve Sheath Menengioma Mimics Like Optic Neuritis; A case report

A 40-years old female patient applied with complaining of a progressive vision loss for 3 months. Systemic symptoms were; headache, tingling in her hands and feet and pain during eye movements. Visual acuity was hand motion on the right eye, 20/20 on the Snellen chart on the left. There was relative afferent pupillary defect on the right eye. In fundoscopic examination, disc edema was met on the right eye and left eye’s fundus examination was normal. A prolongation of p100 wave latency in the Visual Evoked Potentials examination and total visual field defect on automated perimetry test were seen on the right eye. The patient was hospitalized with a pre-diagnosis of optic neuritis. Orbita Magnetic Rezonans was reported the optic nerve sheath menengioma (ONSM). Atypical clinical presentation of an ONSM case that mimiced as optic neuritis, extended to the optic chiasm and lead to a progressive visual loss in a period of 3 months is presented. It is crucial to recognize atypical ONSM cases by the guidence of imaging techniques.

Evaluation of visual pathways using visual evoked potentials in the patients with impaired fasting glucose and impaired glucose tolerance

Purpose: There are many studies on degeneration of the ganglion cells using visual evoked potential (VEP) in Diabetes mellitus (DM). The present study intended to investigate whether the retinopathy findings would be helpful for detecting the degeneration to develop or not in retinal ganglion cells with the VEP test before being detectable in ophthalmoscopic examination on prediabetic patients.Materials and methods: The present study was conducted prospectively after obtaining approval from the Ethics Committee. In our study, the subjects were divided into three groups as impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and normal patients. They also underwent physical, ophthalmological and VEP examination. Three main components of VEP obtained from these groups were N75, P100, and N145 latency and N75-P100 amplitude.Results: The study participants consisted of the IFG group (n: 30, female/male ratio: 21/9; mean age: 49.17 ± 10.52 years), the IGT group (n: 30, female/male ratio: 23/7; mean age: 47.00 ± 11.09 years), and the Control Group (n: 40, female/male ratio: 30/10; mean age: 48.03 ± 10.96 years). Difference in sex and age between the study groups (p > 0.05). P100 latency was found to increase significantly in comparison between the IGT and Control Group for both eyes (p right: 0.003, p left: 0.001) whereas it did not increase significantly in the comparison between the IFG and the Control Group (p right: 0.065, p left: 0.116).Conclusion: It was observed that VEP may be a parameter of predictive value that might be used in evaluating prediabetic cases in terms of retinopathies similar to DM.

The Objective Method of the Evaluation of the Visual Acuity

The paper presents the use of visual evoked potentials VEP to the objective assessment of visual acuity. Methods of using visual evoked potentials (VEP) rely on the assessment of changes of the electrical action potentials generated within the cortex. To diagnose the degree of weakening eyesight a series of studies on healthy people and visually impaired ones were made. Electrophysiological studies of the eye, using noninvasive VEP examination allow a noninvasive and objective assessment of visual acuity. The use of visual evoked potentials gives the objectivity in assessment of visual acuity what may be very important in ophthalmology. This particularly may concern children examination, people with mental retardation and suspected of simulation.

Evaluation of central and peripheral neuropathy in patients with chronic obstructive pulmonary disease.

BackgroundThe aim of the study was to investigate the frequency and characteristics of peripheral nervous system (PNS) and central nervous system (CNS) involvement in COPD.MethodsThe study included 41 COPD patients and 41 healthy volunteers. Electrophysiological studies were carried out: electromyography (EMG) and visual evoked potentials (VEPs). The median nerve, ulnar nerve, common peroneal nerve, and tibial nerve were evaluated for latency, amplitude, and conduction velocity.ResultsThe mean age of patients with COPD was 61.8 years and disease duration 10.3 years. There was no difference between patient and control groups in terms of age, BMI, smoking status, or biochemical parameters. Upon VEP examination, latencies were significantly prolonged and amplitudes shortened in the patient group compared to the control group. In EMG measurements, conduction velocity and amplitudes in all nerves were low in the patient group. Similarly, latencies in all nerves were higher in patients with COPD.ConclusionCentral and peripheral nervous system involvement could develop in patients with moderate–severe COPD, and these patients should be monitored for neuropathic changes in combination with neurological examination.

06-Diagnostic substantiation and current possibilities of VEPS examination

The aim of this introductory lecture is to point out that despite the intensive use of modern imagine techniques (MRI, OCT, etc.), the diagnostic applications of visual evoked potentials (VEPs) need not be obsolete, if not preferable in many cases. This objective, fully non-invasive, low-cost electrophysiological method can detect functional problems of the optic pathway and various brain cortical areas even before a development of the first displayable morphological changes. For the increased sensitivity of VEPs, it is necessary to use a larger spectrum of visual stimuli (activating quite selectively different subsystems of the visual pathway and visual cortex) compared to standards recommended by ISCEV or IFCN. It should include not only flash or pattern-related stimuli (pattern-reversal, pattern-on/off) but also motion-related (motion-onset VEPs) and cognitive visual stimulation. Then, not only the early diagnostics of a large spectrum of neuro-ophthalmological and neuro-psychiatric disorders is possible but also the physiological aging of visual information processing or a drug abuse is recognisable. For a better availability of VEPs examination and their long-term monitoring also in home conditions, we have just introduced a “Mobile (wearable), low-cost device for examination of visual evoked potentials (VEPs)”, the use of which will be demonstrated during the lecture. Acknowledgements: Supported by the project of Charles University “Progres Q40/07”.

Assessment of visual evoked potentials in patients eligible for penetrating keratoplasty.

Corneal opacities can obstruct ophthalmology examination in patients before penetrating keratoplasty (PK).To assess the usefulness of visual evoked potentials (VEPs) in estimating postoperative visual acuity (VA) in patients eligible for (PK) with opaque cornea in 1 eye and good VA in the fellow eye.In this observational study, the mean age of 52 males and 48 females was 57.17 ± 15.99 (21–87 years old). A total of 100 patients eligible for PK underwent an ophthalmological examination including VA and a VEP examination. The P2/P2 ratio was calculated. The correlation coefficient of the VA and the P2/P2 ratio was evaluated 1, 6, and 12 months after PK.A positive correlation of the P2/P2 ratio and VA 1, 6, and 12 months after PK were observed.VEPs including the P2/P2 ratio can be useful in estimating postoperative VA in patients eligible for PK.

Evoked potentials and other guiding factors of conversion from radiologically isolated syndrome to definite multiple sclerosis

Objective: Radiologically Isolated Syndrome (RIS) has become a popular subject recently with quite a number of follow-up and other clinical studies being done. A consensus on the approach to the patient with RIS is being tried to be established. The aim of our study was to assess the role of visual evoked potential (VEP) and somatosensory evoked potential (SEP) as a guiding factor for the conversion from Radiologically Isolated Syndrome (RIS) to definite Multiple Sclerosis (MS). Material and methods: 49 RIS patients who were referred to GATA Haydarpasa Training Hospital Neurology Department between 2011-2015. All of the patients fullfillied the 2009 Okuda criteria for RIS and other differential diagnosis were excluded accordingly. VEP and SEP examinations made during the pre-MS RIS period were scanned retrospectively. For the VEP examination, the P100 latency and amplitudes, for the SEP examination, the P40 latency and amplitude was analysed. Results: 49 patients were included in this study, the mean time of follow-up was 21,8 months. 63% of patients were female, while 37% were male. The mean age was 31,2 years. Among the four patients with abnormal SEPs, MS developed in three of them (75%) over time. This is statistically significant (p = 0.011). VEP and/or SEP was abnormal in 8 patients and MS developed in 4 (50%) of those (p=0.017). The following factors have a positive statistically significant correlation with conversion to MS: Presence of active plaques (r=0.461, p<0.001), presence of more than 9 plaques (r=0.287, p=0.046), VEP and/or SEP pathologies (r=0.402, p=0.004) and number of plaques (r=0.309, p=0.031). The most important factor for the transformation is the presence of active plaque which increases the risk 8.1-fold. The second important factor seems to be the presence of VEP and/or SEP abnormality, but this factor does not reach statistical significance. Conclusion: In the conversion to MS risk from RIS, VEP- SEP examinations are important and should take its place in the follow-up of these patients.

Evoked potential changes in patients with Parkinson's disease.

ObjectivePatients with Parkinson's disease (PD) may have sensory dysfunction, and it can be more easily demonstrated through electrophysiologic testing. We aimed to explore whether the impairment of brainstem visual and auditory passageway exists in PD patients using visual evoked potential (VEP) and brainstem auditory evoked potential (BAEP) examinations.MethodsForty‐two PD cases and thirty controls participated in the study. All subjects underwent the VEP and BAEP examinations. The N75, P100, N145 latencies and P100 amplitude of VEP, the latencies of waves I, III, V and the interpeak latencies (IPL) of waves I–III, III–V, I–V were measured.ResultsThe N75, P100, N145 latencies of VEP, but not the amplitude of P100, were significantly longer in patients with PD than the control group (p < .05). The latencies of wave III and wave V, the IPL of III–V and I–V were all significantly increased compared with control subjects while no significant difference was noted in waves I and I–III IPL.ConclusionOur results found that brainstem visual and auditory passageway may be impaired in PD patients.Significance VEP and BAEP can be served as sensitive measurements in helping prognosis and assessment the severity of the disease.

Pattern- and motion-related visual evoked potentials in HIV-infected adults.

The goal of the current study was to explore visual function in virally suppressed HIV patients undergoing combined antiretroviral therapy (cART) by using pattern-reversal and motion-onset visual evoked potentials (VEPs). The pattern-reversal and motion-onset VEPs were recorded in 20 adult HIV+ patients with a mean age of 38years and CD4 cell counts ≥230×106 cells/L of blood. Nine out of 20 patients displayed VEP abnormalities. Pattern-reversal VEPs pathology was observed in 20% of subjects, and 45% HIV patients had impaired motion-onset VEPs. Five out of 16 neurologically asymptomatic HIV patients had prolonged motion-onset VEP latencies in both eyes. Four neurologically symptomatic patients displayed simultaneously abnormal motion-onset and pattern-reversal VEP latencies: monocular involvement was observed in two patients with Lyme and cytomegalovirus unilateral optic neuritis. Binocular involvement was noted in two patients with cognitive deficits. Correlation analysis between disease duration, CD4 cell count, HIV copies in plasma, MoCA and electrophysiological parameters did not show any significant relationships. The functional changes of the visual system in neurologically asymptomatic virally suppressed HIV patients displayed higher motion-onset VEP sensitivity than in standard pattern-reversal VEP examinations. This promising marker, however, has no significant association with clinical conditions. Further exploration is warranted.

Examination and analysis of diabetic optic neuropathy after cataract surgery

Objective To analyse the characteristics of diabetic optic neuropathy (DON) in cataract patients with diabetes by using fluorescein fundus angiography (FFA), optical coherence tomography (OCT), visual evoked potential (VEP) and perimetry examination. Methods A total of 235 eyes of 125 cataract patients with diabetes were included in the study. These patients received cataract surgery and performed with FFA, OCT, VEP and perimetry examination postoperatively. The examination results and clinical characteristics of diabetic retinopathy (DR) and DON were analyzed. Results Seventy eyes (29.8%) were diagnosed with DR, 75 eyes(31.9%) were diagnosed with DON. FFA in DON patients showed macular edema, optic disc edema, filling defect and optic disc neovascularization. OCT mainly showed macular edema, thickening or atrophy. VEP mainly showed prolonged P100 wave latency or decreased wave amplitude. Perimetry examination showed various kinds of insults. Conclusion DR and DON show a high occurrence rate in diabetes mellitus patient with cataract. FFA plays a key role in the early diagnosis of DR and DON. Retinal ganglion cells are damaged in patients with early DR. Key words: Optic neuropathy, diabetic; Examination, postoperative, cataract; Fundus fluorescein angiography; Optical coherence tomography; Visual evoked potential

Visual evoked potentials in patients after methanol poisoning.

We report the results of the visual evoked potentials (VEP) examination in patients after severe poisoning by methanol. The group of 47 patients (38 males and 9 females) was assembled out of persons who survived an outbreak of poisoning by the methanol adulterated alcohol beverages, which happened in the Czech Republic in 2012-2013. The visual evoked potentials examination was performed using monocular checkerboard pattern-reversal stimulation. Two criteria of abnormality were chosen: missing evoked response, and wave P1 latency > 117 ms. Non-parametric statistical methods (median, range, and the median test) were used to analyze factors influencing the VEP abnormality. The visual evoked potential was abnormal in 20 patients (43%), 5 of them had normal visual acuity on the Snellen chart. The VEP abnormality did not correlate significantly with initial serum concentrations of methanol, formic acid or lactate; however, it showed statistically significant inverse relation to the initial serum pH: the subgroup with the abnormal VEP had significantly lower median pH in comparison with the subgroup with the normal VEP (7.16 vs. 7.34, p = 0.04). The abnormality was not related to chronic alcohol abuse. The visual evoked potentials examination appeared sensitive enough to detected even subclinical impairment of the optic system. Metabolic acidosis is likely to be the key factor related to the development of visual damage induced by methanol. The examination performed with a delay of 1-9 months after the poisoning documented the situation relatively early after the event. It is considered as a baseline for the planned long-term follow-up of the patients, which will make it possible to assess the dynamics of the observed changes, their reversibility, and the occurrence of potential late sequelae.