Effects of disease-modifying therapies on remyelination in multiple sclerosis; evaluation via visual evoked potential test.

BACKGROUND: Assessment of the visual pathway, which is frequently affected by MS, provides the opportunity to measure the remyelination of acute and chronic MS lesions in vivo and non-invasively. VEP can be used in this context. Amplitude is a parameter of axonal loss, whereas latency is an in vivo biomarker of myelin repair. This study aimed to evaluate DMT's neuroprotective and pro-remyelinating potential by evaluating VEP latency and amplitude in MS patients. MATERIALS AND METHODS: A total of 74 patients with relapsing MS who had no evidence of optic neuritis were included in the study. Patient data were retrospectively analyzed and recorded. In the VEP test, latency above 118 ms and amplitude below 5.0 µV were considered abnormal. Classified according to DMTs (injectables, teriflunomide, dimethyl fumarate, fingolimod, cladribine, and alemtuzumab). Visual evoked potential tests, clinical features, and cerebrospinal fluid examinations were evaluated by three independent neurologists and one clinical neurophysiologist. RESULTS: The mean age at diagnosis was 29.2 ± 9.01, and the mean age at first VEP was 34.97 ± 10.64. In women, latency was lower, and amplitude was higher. The mean differences in latency and amplitude were, respectively, latency prolonged by 0.7 ms on the right and 0.5 ms on the left, and amplitude increased by 0.6 µV on the right and 0.37 µV on the left. However, these changes were not statistically significant. Latency worsening was more prominent in those with longer disease duration (p = 0.011). Those with amplitude or latency worsening had higher EDSS (p = 0.016 and 0.013, respectively). DMTs did not affect these changes. CONCLUSION: Prolonged latency is associated with a long disease duration. Deterioration in both amplitude and latency is evident in high EDSS. These results may be an indirect consequence of axonal degeneration dominating remyelination. DMTs do not ameliorate impaired remyelination and neurodegeneration but seem to be sufficient for short-term maintenance of the current state.

Study of Visual Evoked Potentials in Schoolchildren: A Promising Aid to Pediatric Ophthalmology.

Background Visual evoked potential (VEP) is a noninvasive investigation conducted to identify abnormalities in the visual system. It is especially suitable for young children who are unable to express visual symptoms or participate in conventional vision tests. This study was undertaken to examine the VEP among schoolchildren to assess the functionality of their optic pathway. Methodology This short-term observational study was performed in the Clinical Neurophysiology Unit of the Physiology Department of a rural medical college. The study population consisted of 60 schoolchildren aged 7-12. Both eyes were examined for transient pattern reversal VEP recordings using a Recorders & Medicare Systems Electromyography-Evoked Potential recorder (RMS EMG-EP MARK-II Pvt. Ltd., Chandigarh, India). Results VEPs were analyzed for latency and amplitude of the main components, namely P100, N70, and N155. The results showed markedly extended P100 latency in 33.33%, i.e., eight out of 24 eyes of standard (std.) III children. Similar latency prolongation was obtained in 36.36% (eight out of 22) eyes of std. IV, 30% (six of 20 eyes) of std. V, 13.63% (three of 22 eyes) of std. VI, and 50% (eight of 16 eyes) in std. VII and VIII children. A markedly reduced P100 amplitude was observed in two of 20 eyes (10%) of std. V, two of 16 eyes (12.5%) in std. VII and VIII children, amounting to a P100 amplitude abnormality in 5% eyes in toto. The interocular differences in all VEP parameters among the subjects were statistically insignificant. Conclusion In schoolchildren in whom normal latencies and amplitudes were obtained, the presence of reproducible VEPs indicated the normal functional status of their visual pathway. On the other hand, in those children where altered VEP findings were found, it hinted toward complementary information that they may have underlying ocular disorders that were yet to be diagnosed. Hence, this study provides insight into the assessment of visual system function, which is primarily difficult in young children.

Analysis of visual evoked potentials in patients with neurofibromatosis type 1: new concepts.

Introduction: Neurofibromatosis type 1 (NF type 1) is an autosomal dominant disease with typical clinical manifestations, such as skin lesions, Lisch nodules, optic pathway gliomas, and neurofibromas, caused by the mutation of the NF1 gene. Visual evoked potentials (VEP) present a measure of the electrophysiological response of visual cortex to a visual stimulus. The role of VEP in the pathophysiology of NF type 1 is very complex and requires additional research. The Aim: We examined the differences between NF type 1 patients with normal and altered VEP and analyzed the correlation between the prolongation of P100 latency and disease severity. Materials and methods: Two groups were formed: a control group and a study group with NF type 1 patients. Based on the control group analysis, a threshold value for a normal VEP finding of 116 ms was obtained, and it was used to divide the study group into subgroups with normal and altered VEP. We proceeded with examining the differences in clinical manifestations of the disease between the subgroups, after which we checked if there is a correlation between the prolongation of the P100 latency and the severity of the clinical picture according to the Riccardi scale. Statistical analysis was performed using the Pearson chi-square test and the Spearman correlation test in the program SPSS 28.0, with levels of statistical significance p = 0.05 and p = 0.001. Results: In the group with the abnormal VEP we found a statistically significant more frequent occurrence of optic tract glioma (p = 0.008), tumors (p = 0.032), epilepsy (p = 0.043), and cognitive disorders (p = 0.028), while the other clinical signs had an equal prevalence in both groups. A moderately strong correlation (r s = 0.665) was observed between the prolongation of P100 latency and the severity of the clinical picture. Conclusion: Our results showed the important role of VEP in the description of clinical phenotypes of NF type 1. The authors of the study propose VEP to be included in the diagnostic algorithms designed for patients with NF type 1.

Utility of Visual Evoked Potentials (VEPs) study in the evaluation of visual pathway dysfunction in diabetics without retinopathy: correlations with diabetic peripheral neuropathy and other clinical findings.

Aim and objectives: Visual dysfunction in diabetes mellitus (DM) is multifactorial and can be due to vascular disease, and metabolic abnormalities that can affect the retina, optic nerve, and visual pathways. Visual evoked potential (VEP) is an electrophysiological test that can quantify the functional integrity of the visual pathways from the retina via the optic nerves, and optic tracts to the visual cortices. In this study, we aimed to investigate the visual pathway dysfunction among diabetics without retinopathy compared with healthy controls and to look for any correlation with diabetic neuropathy, duration of diabetes, or HbA1c level. Methods: The study included 75 diabetic patients and 75 age and sex-matched controls. VEPs were recorded using the pattern reversal stimulation method on the Medtronic EMG EP machine, and P100 latency and N75-P100 amplitude were recorded in both diabetic patients and healthy controls. Results: Mean P100 latency was significantly prolonged and N75-P100 amplitude significantly reduced among diabetic cases compared to healthy controls (p < 0.001). Among diabetics with peripheral neuropathy, P100 latency was significantly prolonged and N75-P100 amplitude was significantly reduced compared to diabetics without peripheral neuropathy. A significant positive correlation of VEP P100 latency (p < 0.001) and a negative correlation with N75-P100 amplitude (p < 0.001) with duration of disease were also found. Conclusion: VEP changes are observed in diabetics before the development of retinopathy or peripheral neuropathy indicating optic pathway dysfunction, which precedes the development of these complications. Early preclinical visual pathway dysfunction can warrant taking the necessary measures to reduce diabetic complications. Abbreviations: DM = Diabetes Mellitus, VEP = Visual Evoked Potential, HbA1c = Hemoglobin A1 c, MRI = Magnetic Resonance Imaging, EEG = Electroencephalography, P100 = Positive wave peak at latency 100 ms (millisecond), N75 = Negative wave peak at latency 75 ms (millisecond), N145 = Negative wave peak at latency 145 ms (millisecond), OCT = Optical coherence tomography, PRVEP = Pattern Reversal Visual Evoked Potential, NCS = Nerve Conduction Study, SSR = Sympathetic Skin Response, IL1 = Interleukin-1, LIF = Leukemia inhibitory factor, CNTF = Ciliary neurotrophic factor, TNF alpha = Tumor necrosis factor-alpha, TGF-beta = Transforming growth factor-beta.

Prognostic Role of Visual Evoked Potentials in Non-Neuritic Eyes at Multiple Sclerosis Diagnosis.

Introduction: This study aimed to assess the prognostic role of visual evoked potentials (VEPs) of the non-neuritic eye at the diagnosis of multiple sclerosis (MS). Patients and methods: We enrolled 181 MS patients (62% females, mean age at diagnosis: 38 years, standard deviation: 12) at the time of the first diagnostic work-up, including VEPs. We collected P100 latency and N75-P100 amplitude of non-neuritic eyes at diagnosis, and then we calculated the mean values in 127 patients with no history of optic neuritis (ON) or considered the unaffected eye in the remaining. At last follow-up (minimum: one year), disability was evaluated according to MS Severity Score or MSSS (median: 2.44, range: 0.18-9.63). Statistical analysis included Mann-Whitney descriptive analysis, Spearman correlation for independent samples, and linear regression for significant predictors of MSSS. Results: 38/181 patients had P100 latency >115 ms, and 63/181 showed N75-P100 amplitude < 5 microV in the unaffected eyes at MS diagnosis. At last follow-up, MSSS correlated with P100 latency (rho = 0.21, p = 0.004) and N75-P100 amplitude (rho = 0.19, p = 0.009) collected at diagnosis. P100 latency (not N75-P100 amplitude) resulted in a predictor for disability over time (MSSS) in the regression model (along with age at onset, MS course, and disease-modifying treatments). Conclusions: Our study showed a prognostic value of VEPs in clinically unaffected eyes at MS diagnosis to predict future disability, independently from a history of ON.

Evaluation of VEP parameters in patients before and after cardiopulmonary by-pass surgery.

PURPOSE: Coronary bypass surgery is emphasized in aetiology of ischemic optic neuropathy. Our aim in this study was to investigate the pattern visual evoked potentials (PVEP) in patients before and after coronary bypass surgery. METHODS: Thirty-one patients were included in the study. After a full ophthalmological evaluation, PVEP was assesed in the pre and postoperative periods. Operative times, hematological parameters, blood pressures, number of transfusions, body temperatures, anaesthetic drugs and systemic illnesses were recorded for each patient. RESULTS: The mean age of the patients were 59 ± 10.4 years. There was 22 men and 9 women in the study. Only 3 of them needed transfusion during the surgery. The mean duration of the surgery was 3.2 ± 0.7 h. None of the patients had a history of visual disturbance or postoperative ischemic optic neuropathy. The mean VEP P100 amplitude was not statistically significantly different but the mean VEP P100 latency showed statistically significant difference between the preoperative and postoperative periods. (p = 0.014) This significance was more appereant in patients with systemic illnesses. (p = 0.023) There was a positive correlation between the age and VEP P100 latency (r = 0.402, p < 0.05). CONCLUSIONS: Although surgical techniques and equipments are developing each day in the field of cardiopulmonary bypass surgery, the contributing factors such as hypothermia, anemia and diabetes still seem to affect neurophysiological functions even after a noncomplicated surgery.

The relationship between cognitive impairment, cognitive fatigue, and visual evoked potential latency in people with multiple sclerosis.

BACKGROUND: Fatigue in people with multiple sclerosis (PwMS) can impact physical, cognitive, and psychosocial domains of daily life. The experience of fatigue in PwMS is thought to originate from the central nervous system, particularly for the domain of cognitive fatigue. Here, we tested the hypothesis that fatigue scores in PwMS would be significantly associated with an index of neural activity - the latency of the P100 of the visual evoked potential (VEP) - in line with the notion of a centralized origin of fatigue. We predicted that prolonged VEP latency would be associated with greater fatigue, and that this relationship would be the most pronounced within the domain of cognitive fatigue. METHODS: PwMS (n=249) completed the Modified Fatigue Impact Scale (Global, Physical, Cognitive, and Psychosocial scales of the MFIS) and Fatigue Severity Scale. VEP latency was obtained using an alternating checkerboard paradigm. We also examined the influence of depression (Beck Depression Inventory, second edition, BDI-II) and cognitive functioning (NeuroTrax testing battery) on the VEP/fatigue relationship. RESULTS: Surprisingly, we observed that earlier (not later) VEP latency was significantly associated with higher MFIS Cognitive score. The negative relationship between VEP latency and cognitive fatigue was evident in PwMS that had poor cognitive performance as measured by a latent variable that reflected attention, executive function, information processing speed, and motor skills; but a significant relationship was not observed in PwMS that exhibited good performance on this measure. CONCLUSIONS: These findings can be interpreted within a metacognitive framework - greater fatigue may be perceived when neural performance and the level of mental effort expended does not translate to efficient cognitive performance. Cognitive fatigue may be particularly salient in PwMS when neural resources are unable to compensate for cognitive difficulties. The mismatch between the expectation of what ought to occur and what does occur during cognitive performance may be a key feature of the experience of cognitive fatigue for some PwMS.

The usefulness of visual evoked potentials in the assessment of the pediatric multiple sclerosis.

BACKGROUND: To evaluate the significance of visual evoked potentials (VEP) in the early diagnosis of optic neuritis (ON) and detecting clinically silent lesions in pediatric multiple sclerosis (PedMS). This study represents one of the largest series of PedMS which evaluated characteristics of VEP in PedMS patients. METHODS: This was a retrospective study on 52 PedMS patients, aged 7-17 years. VEP analysis were done for all patients, after the first attack of disease and were compared to control subjects according to the pattern-reversal VEP findings. RESULTS: The mean age of patients was 15.65 ± 1.89 years with male to female ratio of 16 (30.8%): 36 (69.2%). All of the patients had a relapsing-remitting course of the disease. ON was discovered on the initial attack in 18 (34.6%) patients, while 30 (57.7%) patients had ON in the second attack. Pathological VEP findings were present in 40 (76.9%) patients, of which 22 (42.3%) PedMS patients had clinically silent lesions. Prolonged latency of P100 waves in the PedMS group was statistically significant when compared to control subjects. The amplitude N1P1 showed a correlation with residual visual deficit. CONCLUSION: Our results show that ON is a common initial manifestation of PedMS in the Serbian PedMS population. The prolonged P100 latency is the main indicator of ON. VEP is an objective, fast and accessible diagnostic method for detecting clinical and subclinical lesions. Thus, VEP deserves evaluation to be considered as an additional criterion for PedMS diagnosis.

Normative values of visual evoked potentials in Northeastern of Iran.

PURPOSE: Visual evoked potentials (VEPs) provide important diagnostic information related to the functional integrity of the visual pathways. The aim of this study was to establish normative values of different components of pattern reversal VEPs on Iranian normal adult subjects. METHODS: Monocular and binocular pattern reversal VEPs were recorded on 59 healthy participants (22.55±3.79 years old) using the Roland RETI system for two check sizes of 15 and 60min of arc. The measured VEP components were the latencies of N75, P100, N135 and amplitude of N75-P100. RESULTS: Repeated measures ANOVA showed that viewing eye condition has a significant impact on the amplitude of N75-P100 (P<0.001, F=13.89). Also, the effect of check size on the latencies of N75, P100, N135, amplitude of N75-P100 (P≤0.010), as well as the intraocular difference of P100 latency and amplitude N75-P100 (P=0.007) was significant. More specifically, the amplitude of N75-P100 in both check sizes significantly differed between gender groups (P<0.023). CONCLUSION: According to the results of this study, VEPs components are affected by the stimulus size, monocular and binocular recording conditions and gender. Therefore, it is necessary to determine the normative values of VEPs in each population, so that the results could be used in clinical studies.

Visual Evoked Potentials: Normative Values and Gender Differences.

INTRODUCTION: Visual evoked potentials (VEP) are used to assess the visual pathways through the optic nerves and brain. A normal VEP response to a pattern-reversal stimulus is a positive mid occipital peak that occurs at a mean latency of 100 ms. VEP may be affected by variety of physiological factors including age, sex, visual acuity and pupillary size. AIMS AND OBJECTIVES: The present study was performed on healthy medical students to determine the normative values and to investigate the effect of sex and anthropometric parameters on visual evoked potentials. MATERIALS AND METHODS: The study was conducted on 100 healthy medical students of Government Medical College, Patiala in the age group of 17-20 years, in which there were 50 males and 50 females. The anthropometric parameters including age, height, weight, BMI, BSA and Head circumference were recorded in all the subjects. VEP was recorded with a PC based, 2 channel, RMS EMG EP mark II machine and standard silver-silver chloride disc electrodes. A VEP monitor displaying checker board was used to give the pattern reversal stimulus. The VEP parameters recorded were latencies to N70, P100 and N155 waves, and peak to peak amplitude of P100 wave. RESULTS: Our results showed that the latencies of N70, P100 and N155 waves were significantly longer in males as compared to females. The amplitude of P100 wave was higher in females in both left and right eye as compared to males. No significant correlation was found between VEP parameters and head circumference in both male and female subjects in our study. CONCLUSION: Gender is an important variable affecting the VEP. The exact reason of gender difference is not clear, but it may be related to anatomical or endocrinal differences in the two sexes.

Influence of visual angle on pattern reversal visual evoked potentials.

PURPOSE: The aim of this study was to find whether the visual evoked potential (VEP) latencies and amplitude are altered with different visual angles in healthy adult volunteers or not and to determine the visual angle which is the optimum and most appropriate among a wide range of check sizes for the reliable interpretation of pattern reversal VEPs (PRVEPs). MATERIALS AND METHODS: The present study was conducted on 40 healthy volunteers. The subjects were divided into two groups. One group consisted of 20 individuals (nine males and 11 females) in the age range of 25-57 years and they were exposed to checks subtending a visual angle of 90, 120, and 180 minutes of arc. Another group comprised of 20 individuals (10 males and 10 females) in the age range of 36-60 years and they were subjected to checks subtending a visual angle of 15, 30, and 120 minutes of arc. The stimulus configuration comprised of the transient pattern reversal method in which a black and white checker board is generated (full field) on a VEP Monitor by an Evoked Potential Recorder (RMS EMG. EPMARK II). The statistical analysis was done by One Way Analysis of Variance (ANOVA) using EPI INFO 6. RESULTS: In Group I, the maximum (max.) P100 latency of 98.8 ± 4.7 and the max. P100 amplitude of 10.05 ± 3.1 µV was obtained with checks of 90 minutes. In Group II, the max. P100 latency of 105.19 ± 4.75 msec as well as the max. P100 amplitude of 8.23 ± 3.30 µV was obtained with 15 minutes. The min. P100 latency in both the groups was obtained with checks of 120 minutes while the min. P100 amplitude was obtained with 180 minutes. A statistically significant difference was derived between means of P100 latency for 15 and 30 minutes with reference to its value for 120 minutes and between the mean value of P100 amplitude for 120 minutes and that of 90 and 180 minutes. CONCLUSION: Altering the size of stimulus (visual angle) has an effect on the PRVEP parameters. Our study found that the 120 is the appropriate (and optimal) check size that can be used for accurate interpretation of PRVEPs. This will help in better assessment of the optic nerve function and integrity of anterior visual pathways.

Correlation of pattern reversal visual evoked potential parameters with the pattern standard deviation in primary open angle glaucoma.

AIM: To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation (PSD) of Humphrey visual field could be associated with visual evoked potential (VEP) parameters of patients having primary open angle glaucoma (POAG). METHODS: Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential (PRVEP) were assessed in 100 patients with POAG. The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated (full field) and displayed on VEP monitor (colour 14″) by an electronic pattern regenerator inbuilt in an evoked potential recorder (RMS EMG EP MARK II). RESULTS: The results of our study indicate that there is a highly significant (P<0.001) negative correlation of P100 amplitude and a statistically significant (P<0.05) positive correlation of N70 latency, P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student's t-test. CONCLUSION: Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values. Conversely, as PSD increases the magnitude of VEP excursions were found to be diminished.

Visual evoked potentials in neuromyelitis optica and its spectrum disorders.

Optic neuritis (ON) is a key feature of neuromyelitis optica (NMO). Recently, NMO patients of predominantly Afro-Brazilian origin were evaluated by visual evoked potentials (VEPs) and showed marked amplitude reductions. Here, we analyzed VEPs in a predominantly Caucasian cohort, consisting of 43 patients with definite NMO, 18 with anti-aquaporin (AQP) 4 antibody-seropositive NMO spectrum disorders and 61 matched healthy controls. We found reduced amplitudes in only 12.3%, prolonged latencies in 41.9% and a lack of response in 14.0% of NMO eyes. Delayed P100 latencies in eyes without prior ON suggested this was a subclinical affection. The data indicate heterogenous patterns in NMO, warranting further investigation.

Pattern Visual Evoked Potential as a Predictor of Occlusion Therapy for Amblyopia

PURPOSE: This study was conducted to investigate the role of the pattern visual evoked potential (pVEP) as a predictor of occlusion therapy for patients with strabismic, anisometropic, and isometropic amblyopia. The secondary aim was to compare the characteristics of pVEP between strabismic and anisometropic amblyopia. METHODS: This retrospective comparative case series included 120 patients who had received occlusion therapy or a glasses prescription for correction of strabismic, anisometropic, and isometropic amblyopia (20 patients had strabismic amblyopia, 41 patients had anisometropic amblyopia, and 59 patients had isometropic amblyopia). For each patient, the value of the P100 latency on pVEP at the time of the initial diagnosis of amblyopia was collected. Subsequently, the P100 latency was compared according to types of amblyopia. Fifty of 120 patients (7 patients with strabismic amblyopia, 21 patients with anisometropic amblyopia, and 22 patients with isometropic amblyopia) who were followed-up for longer than 6 months were divided into two groups based on the value of their P100 latency (Group 1, P100 latency 120 msec or less; Group 2, P100 latency longer than 120 msec.) The amount of visual improvement after occlusion therapy or glasses was compared between two study groups. RESULTS: The mean P100 latency was 119.7+/-25.2 msec in eyes with strabismic amblyopia and 111.9+/-17.8 msec in eyes with non-strabismic (anisometropic or isometropic) amblyopia (p=0.213). In Group 1, the mean visual improvement after occlusion therapy or glasses was 3.69+/-2.14 lines on Dr. Hahn's standard test chart; in Group 2, the mean improvement was 2.27+/-2.21 lines (p=0.023). CONCLUSIONS: The P100 latency on pVEP at the time of initial diagnosis was significantly related to the visual improvement after occlusion therapy or glasses in patients with strabismic, anisometropic, and isometropic amblyopia. Therefore, it was presumed that patients with a delayed P100 latency might have less visual improvement after occlusion therapy or glasses. In addition, there was no apparent difference in P100 latency between patients with strabismic and non-strabismic (anisometropic or isometropic) amblyopia.

The Change of Visual Evoked Potential in Patients with Myopia in Correction of Refraction

OBJECTIVE: Multiple factors including age, sex, habituation, refraction, cooperation and technical variables are associated with P100 latency of Visual evoked potential (VEP). So we tried to evaluate the P100 latency of visual evoked potential according to refraction. METHOD: We studied 28 patients (12 males, 16 females) with myopia. Subjects were divided into 3 groups (mild, moderate, severe myopia) according to refraction and we evaluated the results of VEP studies. RESULTS: Mean values of refraction and latency (P100) of naked eyes were -4.27 D, 103.95 msec. and those of corrected eyes (in glasses) were -0.25 D, 100.59 msec. Respectively, in mild, moderate and severe myopia, the each P100 latency of naked eyes were 101.27 msec, 102.59 msec, 107.99 msec and those of corrected eyes were 98.33 msec, 100.58 msec, 102.19 msec respectively (p<0.05). There was significant negative correlation between refraction and P100 latency in myopia. CONCLUSION: Our results suggested that there were significant changes in VEP (P100 latency) according to refraction. In performing the VEP study, we should consider the refraction and visual acuity.

Effect of Refractive Error on the P100 Latency of Visual Evoked Response

OBJECTIVE: Absolute or relative increase in the latency of the major surface positive component is almost invariably found in patients with demyelination optic neuropathy. Using the pattern- reversal method, our study illustrates the significant changes in the latency of the P100 component when refractive errors are introduced to defocus in normal person. METHOD: Four women and ten men aged 20 to 27 years were selected after a thorough ophthalmological assessment. Visual acuity (VA) was 6/6 or better in all subject and none had dyschromatopsia or significant astigmatism. Refractive errors were created by the combined standard lenses. RESULTS: The mean value of P100 latency were as follows: 93.74 +/- 3.30 msec, naked eyes; 98.14 +/- 7.37 msec, the +2/+x 90 lens; 96.50 +/- 3.76 msec, the +1/ +1 x90 lens; 94.55 +/- 4.20 msec, the -1/ -1x90; 96.29 +/- 2.88 msec, the -2/ -2 x90 lens. The P100 latencies showed singnificant standard lens except with -1/ -1 x90 lens. The P100 latency was prolonged according to the progression of refractive error. CONCLUSION: Because a relative or absolute prolongation of P100 latency is often found in cases of suspected multiple sclerosis, and because of their similarity to the findings of our study, we would emphasize that refractive errors should be reduced or eliminated to minimize the false-positive results.

P100 Latency in Normal Persons by Pattern Reversal VEP and Flash VEP

The Flash Light Emitted Diode Flash Visual Evoked Potential(Flash VEP) is useful when patients are unable to cooperate sufficiently for a Pattern Reversal Visual Evoked Potential(RP-VEP). In order to evaluate the clinical utility of Flash VEP, we performed the PR-VEP and Flash VEP in 208 eyes of 104 normal persons. The average P100 latency(LaP100) was analyzed according to check size, age, sex, and the laterality of the eye. The LaP100 of PR-VEP stimulated with 8 X 8(120' X 96'), 16 X 16(60' X 48'), 32 X 32 (30' X 24') and 64 X 64(15' X 12') check size were 98.88 +/- 7.57msec(mean S.D msec) , 97.68 +/- 7.44msec, 96.31 +/- 7.21msec, 101.20 +/- 7.81msec, respectively. The LaP100 of PR-VEP stimulated with 32 X 32 check size at 3rd, 4th, 5th, 6th and 7th decades were 93.95 +/- 5.61msec, 94.70 +/- 7.71msec, 92.92 +/- 6.28msec, 97.78 +/- 6.24 msec, 102.79 +/- 5.27msec, respectively. The LaP100 of PR-VEP remained relatively stable until over 6th decade when it increased significantly (p0.05), and between male and female(p>0.05) in the LaP100 of both VEP. These results showed that LaP100 of PR-VEP changes according to the check size and patient's age. We should interprete the LaP100 of PR-VEP or Flash VEP after the processing of averaging its P100 according to the patient's.