Interocular Latency Research Articles

Assessing the visual afferent pathway with the multifocal visual evoked potentials in the radiologically isolated syndrome

The early identification of individuals with radiologically isolated syndrome (RIS) who are at an elevated risk of progressing to multiple sclerosis (MS) is essential for making informed treatment decisions. This study aimed to evaluate the predictive potential of multifocal Visual Evoked Potentials (mfVEP) measures in individuals with RIS with respect to their conversion to MS. A prospective observational cohort study was conducted, involving 21 individuals with RIS recruited from a MS center. Baseline assessments, including mfVEP, magnetic resonance imaging (MRI), and clinical examinations, were performed, and participants were longitudinally followed for up to 24 months. The primary outcome measures were the conversion to MS. Over a clinical follow-up period of 24 months, five individuals (5/21) with RIS progressed to MS. MfVEP amplitude responses (interocular and monocular probability analysis) demonstrated abnormal cluster visual field defects in 47.6% of RIS eyes at baseline, whereas multifocal VEP latency analysis showed significant delays in 38.4%. A reduction in interocular amplitude [OR = 0.036, (95% CI 0.003–0.503); P = 0.014], monocular amplitude [OR = 0.083, (95% CI 0.007–0.982); P = 0.048], and a prolonged interocular latency [OR = 0.095, (95% CI 0.009–0.972); P = 0.047] were associated with a higher relative risk of clinical conversion at the 2-year follow-up. Multifocal VEP may serve as a novel and independent risk factor for predicting the conversion to MS in individuals with Radiologically Isolated Syndrome.

Is the prolongation latency of visual evoked potentials a pathological sign in children with Down’s syndrome without ocular abnormalities? Case–control study of children with Down’s syndrome

ObjectiveTo evaluate retino-cortical function in children with Down’s syndrome (DS) and no evident ocular abnormalities beyond mild refractive error, by recording visual evoked potentials (VEP) in response to pattern-reversal stimuli...

Prognosticators for Visual Outcome in Indirect Traumatic Optic Neuropathy: A Prospective Cohort Study.

Introduction Traumatic optic neuropathy (TON), with indirect TON as its more prevalent form, is a dreadful cause of severe visual dysfunctions. The condition is known to have a contentious treatment plan and poor visual sequelae; hence, the assessment of prognostic signs becomes valuable. Prospective studies evaluating important predictors of visual recovery after traumatic optic nerve injury can particularly be helpful in a longitudinal observation. The possible roles of clinical variables need to be assessed. Absent visual evoked potential (VEP) records as a crucial finding associated with TON has reportedly valuable prognostic significance. This also needs to be explored. Hence, the study sought to determine the role of prognosticators in the visual outcome of the patients, with a focus on evaluating the role of VEPs in the severity and prognosis of indirect TON. Methods A prospective observational study involving 40 patients with indirect TON was conducted. Ocular, neuro-ophthalmological, radiological, and neurophysiological variables, including flash VEP, were investigated at their initial visit and followed up until the end of six months. Final visual acuity was the primary outcome variable studied. Paired t-test was used to perform the comparison between the flash VEP variables for normal and affected eyes at the initial visit. Pearson correlation coefficient was computed for obtaining the association of initial visual acuity and flash VEP variables with the outcome variable. Relative risk was calculated and analysed for the prognosticators in univariate analysis. Statistical significance was defined as p < 0.05. Results Statistically significant variations in mean P100 latency, N75-P100, and P100-N145 amplitudes compared between normal and affected eyes in the patients at the initial visit were obtained (p < 0.0001; paired t-test). Pearson correlation coefficient for initial visual acuity and flash VEP variable as independent variables and final visual acuity as the dependent variable were statistically significant (p < 0.05). The relative risks for prognosticators with a statistically significant range of confidence intervals were poor initial visual acuity, greater relative afferent pupillary defect (RAPD) grades, deranged flash VEP variables (absent VEP, reduction in amplitude ratio (>50%), and increased interocular latency differences), loss of consciousness during injury, age greater than 40 years, and lack of improvement after 48 hours of steroid treatment. Conclusion The identified negative prognosticators may be helpful in deciding the kind of therapeutic approach and predicting the visual outcome in patients with indirect TON.

Individual differences in visual evoked potential latency are associated with variance in brain tissue volume in people with multiple sclerosis: An analysis of brain function-structure correlates

Visual evoked potentials (VEP) index visual pathway functioning, and are often used for clinical assessment and as outcome measures in people with multiple sclerosis (PwMS). VEPs may also reflect broader neural disturbances that extend beyond the visual system, but this possibility requires further investigation. In the present study, we examined the hypothesis that delayed latency of the P100 component of the VEP would be associated with broader structural changes in the brain in PwMS. We obtained VEP latency for a standard pattern-reversal checkerboard stimulus paradigm, in addition to Magnetic Resonance Imaging (MRI) measures of whole brain volume (WBV), gray matter volume (GMV), white matter volume (WMV), and T2-weighted fluid attenuated inversion recovery (FLAIR) white matter lesion volume (FLV). Correlation analyses indicated that prolonged VEP latency was significantly associated with lower WBV, GMV, and WMV, and greater FLV. VEP latency remained significantly associated with WBV, GMV, and WMV even after controlling for the variance associated with inter-ocular latency, age, time between VEP and MRI assessments, and other MRI variables. VEP latency delays were most pronounced in PwMS that exhibited low volume in both white and gray matter simultaneously. Furthermore, PwMS that had delayed VEP latency based on a clinically relevant cutoff (VEP latency ≥ 113 ms) in both eyes had lower WBV, GMV, and WMV and greater FLV in comparison to PwMS that had normal VEP latency in one or both eyes. The findings suggest that PwMS that have delayed latency in both eyes may be particularly at risk for exhibiting greater brain atrophy and lesion volume. These analyses also indicate that VEP latency may index combined gray matter and white matter disturbances, and therefore broader network connectivity and efficiency. VEP latency may therefore provide a surrogate marker of broader structural disturbances in the brain in MS.

Prolonged visual evoked potential latency predicts longitudinal worsening of fatigue in people with multiple sclerosis

BackgroundFatigue is a common problem experienced by people with multiple sclerosis (PwMS) and can impact physical, cognitive, and psychosocial aspects of daily living and quality of life. The tracking of meaningful longitudinal change in subjective fatigue that occurs as a result of MS activity may be enhanced by incorporating objective neurophysiological measures into longitudinal assessment. To examine this possibility, we examined the longitudinal relationship between visual evoked potential (VEP) measures and a variety of fatigue measures over an approximately two-year period in PwMS. MethodsVEP measures were obtained using a checkerboard pattern-reversal paradigm. Fatigue was assessed with the Modified Fatigue Impact Scale (MFIS Global, Physical, Cognitive, and Psychosocial subscales) and the Fatigue Severity Scale (FSS) questionnaires. Multiple linear regression analyses were conducted in which the change in each fatigue scale score from baseline to follow-up (T1-to-T2) served as the outcome variables for separate models. Predictor variables included the peak latency of the P100 component of the VEP (maximum peak among the two eyes) and the inter-ocular latency (IOL) at T1, the T1-to-T2 change score for maximum VEP latency and IOL, and the fatigue score at T1 that corresponded to each outcome measure. ResultsProlonged baseline VEP latency was a significant predictor of the T1-to-T2 increase in MFIS Global score, and increased VEP latency from baseline to follow-up was significantly associated with MFIS Cognitive score over the same time period. Furthermore, VEP latency measures in these two models were better predictors of changes in fatigue than baseline fatigue scores were, based on the magnitude of the standardized beta coefficients. Subsequent post-hoc analyses revealed that the relationship between change in VEP latency and change in MFIS Cognitive score was evident primarily for PwMS that had elevated MFIS Cognitive score at baseline. ConclusionThe present study provides novel evidence that prolonged VEP latency is predictive of worsening of global and cognitive fatigue in PwMS. VEP latency measures may therefore provide clinical utility for monitoring changes in fatigue in PwMS, when used in conjunction with other clinical tools.

Longitudinal assessment of the relationship between visual evoked potentials and cognitive performance in multiple sclerosis

ObjectiveVisual evoked potentials (VEPs) can provide insight into disease activity in people with multiple sclerosis (PwMS). However, few studies have tracked concurrent changes in VEPs and cognitive functioning over time in MS. To address this, we examined the longitudinal relationship between VEP and cognitive performance in PwMS over a two-year period. MethodsAt baseline (T1) and follow-up (T2, 2.14 years after baseline, on average), P100 peak latency and inter-ocular latency (IOL) between eyes were calculated from the VEP elicited for checkerboard pattern-reversal stimuli. Cognitive performance was assessed for seven different domains (NeuroTrax battery). The potential for VEP variables to predict the T1-to-T2 change in cognitive performance was assessed in a series of multiple linear regression models. ResultsBaseline IOL and VEP latency were significantly associated with T1-to-T2 change in information processing speed. Post-hoc analyses indicated that PwMS that had both prolonged VEP latency and elevated IOL at baseline tended to exhibit greater information processing speed decline. Increase in VEP latency from T1-to-T2 was also associated with decline in psychomotor function over time. ConclusionsThese findings provide evidence that VEP measures can serve as valuable prognostic indicators of longitudinal cognitive change in PwMS. SignificanceVisual system neurophysiology corresponds with changes in speeded cognitive performance in MS.

Visual evoked potential latency predicts cognitive function in people with multiple sclerosis.

Prior studies have reported an association between visual evoked potentials (VEPs) and cognitive performance in people with multiple sclerosis (PwMS), but the specific mechanisms that account for this relationship remain unclear. We examined the relationship between VEP latency and cognitive performance in a large sample of PwMS, hypothesizing that VEP latency indexes not only visual system functioning but also general neural efficiency. Standardized performance index scores were obtained for the domains of memory, executive function, visual-spatial processing, verbal function, attention, information processing speed, and motor skills, as well as global cognitive performance (NeuroTrax battery). VEP P100 component latency was obtained using a standard checkerboard pattern-reversal paradigm. Prolonged VEP latency was significantly associated with poorer performance in multiple cognitive domains, and with the number of cognitive domains in which performance was ≥ 1 SD below the normative mean. Relationships between VEP latency and cognitive performance were significant for information processing speed, executive function, attention, motor skills, and global cognitive performance after controlling for disease duration, visual acuity, and inter-ocular latency differences. This study provides evidence that VEP latency delays index general neural inefficiency that is associated with cognitive disturbances in PwMS.

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.

Evoked potentials in diagnosis of visual dysfunction in amateur boxers

ABSTRACTObjective: Injuries with varying degrees of temporary or permanent visual dysfunction are common in boxing. This study presents clinical diagnostic information regarding the functional integrity of the visual system in elite amateur boxers. The objective of this study was to assess the presence of normal or abnormal pattern visual evoked potentials (VEP). VEP in boxers were analyzed in relation to the nonathletic group and years of boxing activity.Methods: Clinical examination involved 31 boxers (21 male and 10 female) and 31 controls homogeneous in terms of age and gender. Pattern-reversal VEP elicited by checkerboard stimuli with large (LC) and small checks (SC) under monocular condition were applied. The latency and amplitude of N75, P100 and N135 components of the VEP waveform were analyzed. Absolute values and interocular differences of P100 latency and N75-P100 amplitude were used in determining VEP abnormalities.Results: Individual analysis showed prolonged P100 latency in both eyes in one male boxer. Interocular P100 latency differences beyond 8 ms were observed in three male boxers. The N75-P100 amplitude of four boxers exceeded the normal range in both eyes for the LC stimulation and one boxer for the SC stimulation. Interocular N75-P100 amplitude differences beyond the normal range in two cases for both the LC and the SC stimulation were confirmed. There was a positive correlation between years of boxing activity and N75 latency in SC (R = 0.480, p < 0.05) and N75-P100 amplitude in LC (R = -0.370, p < 0.05).Conclusion: Long-term boxing training may cause impairments in neural conductivity in the visual pathway. VEP seem to be a valuable tool in the neurophysiological diagnosis of visual function in contact sports. They can be recommended as a systematical examination for boxers during training processes for the indication and reduction in the incidence of vision-threatening injuries.

Empirical mode decomposition processing to improve multifocal-visual-evoked-potential signal analysis in multiple sclerosis.

ObjectiveTo study the performance of multifocal-visual-evoked-potential (mfVEP) signals filtered using empirical mode decomposition (EMD) in discriminating, based on amplitude, between control and multiple sclerosis (MS) patient groups, and to reduce variability in interocular latency in control subjects.MethodsMfVEP signals were obtained from controls, clinically definitive MS and MS-risk progression patients (radiologically isolated syndrome (RIS) and clinically isolated syndrome (CIS)). The conventional method of processing mfVEPs consists of using a 1–35 Hz bandpass frequency filter (XDFT).The EMD algorithm was used to decompose the XDFT signals into several intrinsic mode functions (IMFs). This signal processing was assessed by computing the amplitudes and latencies of the XDFT and IMF signals (XEMD). The amplitudes from the full visual field and from ring 5 (9.8–15° eccentricity) were studied. The discrimination index was calculated between controls and patients. Interocular latency values were computed from the XDFT and XEMD signals in a control database to study variability.ResultsUsing the amplitude of the mfVEP signals filtered with EMD (XEMD) obtains higher discrimination index values than the conventional method when control, MS-risk progression (RIS and CIS) and MS subjects are studied. The lowest variability in interocular latency computations from the control patient database was obtained by comparing the XEMD signals with the XDFT signals. Even better results (amplitude discrimination and latency variability) were obtained in ring 5 (9.8–15° eccentricity of the visual field).ConclusionsFiltering mfVEP signals using the EMD algorithm will result in better identification of subjects at risk of developing MS and better accuracy in latency studies. This could be applied to assess visual cortex activity in MS diagnosis and evolution studies.

Effects of Reduced Acuity and Stereo Acuity on Saccades and Reaching Movements in Adults With Amblyopia and Strabismus

Our previous work has shown that amblyopia disrupts the planning and execution of visually-guided saccadic and reaching movements. We investigated the association between the clinical features of amblyopia and aspects of visuomotor behavior that are disrupted by amblyopia. A total of 55 adults with amblyopia (22 anisometropic, 18 strabismic, 15 mixed mechanism), 14 adults with strabismus without amblyopia, and 22 visually-normal control participants completed a visuomotor task while their eye and hand movements were recorded. Univariate and multivariate analyses were performed to assess the association between three clinical predictors of amblyopia (amblyopic eye [AE] acuity, stereo sensitivity, and eye deviation) and seven kinematic outcomes, including saccadic and reach latency, interocular saccadic and reach latency difference, saccadic and reach precision, and PA/We ratio (an index of reach control strategy efficacy using online feedback correction). Amblyopic eye acuity explained 28% of the variance in saccadic latency, and 48% of the variance in mean saccadic latency difference between the amblyopic and fellow eyes (i.e., interocular latency difference). In contrast, for reach latency, AE acuity explained only 10% of the variance. Amblyopic eye acuity was associated with reduced endpoint saccadic (23% of variance) and reach (22% of variance) precision in the amblyopic group. In the strabismus without amblyopia group, stereo sensitivity and eye deviation did not explain any significant variance in saccadic and reach latency or precision. Stereo sensitivity was the best clinical predictor of deficits in reach control strategy, explaining 23% of total variance of PA/We ratio in the amblyopic group and 12% of variance in the strabismus without amblyopia group when viewing with the amblyopic/nondominant eye. Deficits in eye and limb movement initiation (latency) and target localization (precision) were associated with amblyopic acuity deficit, whereas changes in the sensorimotor reach strategy were associated with deficits in stereopsis. Importantly, more than 50% of variance was not explained by the measured clinical features. Our findings suggest that other factors, including higher order visual processing and attention, may have an important role in explaining the kinematic deficits observed in amblyopia.

Electrophysiological evaluation in patients with type 2 diabetes mellitus by pattern reversal visual evoked potentials

Background: A more general involvement of the nervous system in diabetes, affecting not only the peripheral but also the central nervous system has been increasingly suggested over the last two decades. Electrophysiological investigations in the form of visual evoked potentials (VEPs) can be very sensitive and valuable method in evaluating central neural conduction in diabetics before the overt manifestations of ophthalmologic involvement. Aims and Objectives: This study was planned to detect visual dysfunctions in type 2 diabetics at earlier stages by recording pattern reversal VEPs (PRVEPs). Materials and Methods: PRVEP was recorded in 100 subjects (50 patients with type 2 diabetes and 50 controls). Mean latencies of N75, P100 and N145 waves, interocular latency differences (for P100 waves) and N75-P100 amplitude were compared between diabetics and the controls by unpaired t-test. P < 0.05 was considered as significant. Results: A statistically significant increase in mean P100 latency (P < 0.0001) and interocular latency difference (P < 0.001) along with the reduction in N75-P100 amplitude (P < 0.0001) was revealed in diabetics as compared to the controls. Mean N75 and N145 latencies exhibited increase in diabetics but without statistical significance. Conclusion: Electrophysiological alterations in the form of abnormal VEPs are registered in type 2 diabetes before clinically detectable ophthalmologic impairment. VEPs should be employed for assessing the visual functions in diabetics to ameliorate the prognosis of the condition.

Visual pathway abnormalities in tuberculous meningitis

Ophthalmological complications are common and disabling in patients with tuberculous meningitis. We aimed to study the visual pathway abnormalities in patients with tuberculous meningitis. Forty-three patients with tuberculous meningitis were subjected to visual evoked responses (VER) and neuroophthalmologic assessment. Neuroophthalmologic assessment revealed abnormalities in 22 (51.3%) patients. VER were found to be abnormal in 27 (62.8%) patients. The VER abnormalities included prolonged P100 latencies with relatively normal amplitude and significant interocular latency differences. Visual pathways abnormalities are common in patients with tuberculous meningitis and are often subclinical. Pathophysiologic explanations for electrophysiological abnormalities on VER in these patients are incompletely understood and needs further exploration.

Saccadic latency in amblyopia.

We measured saccadic latencies in a large sample (total n = 459) of individuals with amblyopia or risk factors for amblyopia, e.g., strabismus or anisometropia, and normal control subjects. We presented an easily visible target randomly to the left or right, 3.5° from fixation. The interocular difference in saccadic latency is highly correlated with the interocular difference in LogMAR (Snellen) acuity—as the acuity difference increases, so does the latency difference. Strabismic and strabismic-anisometropic amblyopes have, on average, a larger difference between their eyes in LogMAR acuity than anisometropic amblyopes and thus their interocular latency difference is, on average, significantly larger than anisometropic amblyopes. Despite its relation to LogMAR acuity, the longer latency in strabismic amblyopes cannot be attributed either to poor resolution or to reduced contrast sensitivity, because their interocular differences in grating acuity and in contrast sensitivity are roughly the same as for anisometropic amblyopes. The correlation between LogMAR acuity and saccadic latency arises because of the confluence of two separable effects in the strabismic amblyopic eye—poor letter recognition impairs LogMAR acuity while an intrinsic sluggishness delays reaction time. We speculate that the frequent microsaccades and the accompanying attentional shifts, made while strabismic amblyopes struggle to maintain fixation with their amblyopic eyes, result in all types of reactions being irreducibly delayed.

Role of Visual Evoked Potentials in Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic, demyelinating disease of the central nervous system (CNS) affecting young adults and is considered as the leading cause of non traumatic neurological disability of young adults affecting nearly 2 million people worldwide. The pathogenesis of MS is at best incompletely understood. There are several proposed mechanisms that may be important in the production of MS plaques: autoimmunity, environment and heredity. Deviation of immune responses in a genetically susceptible patient plays a central role in its pathogenesis. Electrophysiological, spinal tap and Radiological tools are important laboratory investigations and have added so much to the clinical diagnosis and for the classification of MS. It was found that visual function and conduction has been changed in patients with multiple sclerosis.Objectives: The aims of the study is to estimate and evaluate the visual evoked potential (VEP) parameters in patients with MS and its relation to their disability degree (using the expanded disability status scale score "EDSS") and visual presentation of them in comparison with healthy individuals.Patients and Methods: 112 patients with multiple sclerosis and 50 subjects without any neurological or psychiatric diseases as control group were recruited in this study. The cases were collected from Baghdad teaching hospital, MS center, Baghdad, Iraq at the period from May 2012 to April 2013, and studied at the unit of electrophysiology in Al-Shaheed Ghazi Al-Hareri Hospital in the Medical city. All patients and control groups were tested for VEP.Results: The present study showed a significant increase in the P100 latency and inter-ocular (IO) latency difference and non statistical significant decrease in the IO amplitude difference in patients group than the control group. Also among patients group there was positive linear correlation between the severity of the disease measured by EDSS score and P100 latency while negative linear correlation with the amplitude. Conclusion: There was a higher percent of patients with defective VEP parameters and so their visual pathway even if it was asymptomatic, in addition to their relation with patients` disability than the control group, making it easy to quantify and predict MS disability objectively. Keywords: Multiple sclerosis, Expanded Disability Status Scale, VEP.

Diagnostic value of visual evoked potentials for clinical diagnosis of multiple sclerosis.

Prolonged latency of visual evoked potentials (VEP) has been used to identify clinically silent lesions in multiple sclerosis (MS) suspects. The objective of this study was to determine the reliability of VEP to predict the development of MS in MS suspects. Retrospective hospital records of MS suspects were evaluated. VEP was analyzed together with subsequent diagnostic confirmation of MS by McDonald diagnostic criteria for MS-2005. MS developed in 12 of 35 patients (34 %) and 23 (66 %) failed to exhibit diagnostic characteristics. P100 latencies and interocular latency differences were longer in clinically definite multiple sclerosis (CDMS) than non-CDMS patients (p = 0.002, 0.001, respectively). All patients in the subsequent MS group had P100 latencies longer than102 ms, a mean of our MS-free subjects thus providing 100 % of sensitivity. No patient developed MS with a P100 latency <102 ms. Brain MRI lesions associated significantly with developing CDMS (p = 0.001). Predictability of developing CDMS was highest when criteria for P100 latency, interocular latency difference, and brain MRI lesions were combined. MS suspects with a P100 latency longer than mean of MS-free subjects are more likely to develop MS than those with lower values. VEP latency combined with MRI could improve the accuracy of MS prediction.

Multifocal Visual Evoked Potentials in Unilateral Compressive Optic Neuropathy Secondary to Orbital Tumors

To evaluate the effects of unilateral compressive optic neuropathy secondary to orbital tumors and the removal of the tumors on amplitude and latency of multifocal visual evoked potentials (mfVEPs) and to compare these responses with visual field defects seen on static automated perimetry. Static automated and mfVEP recordings were obtained from 14 patients with orbital tumors affecting one optic nerve. Monocular and interocular amplitude and latency analyses were performed. The change in the mfVEP amplitude agreed with visual field findings with regard to topography and severity of deviation from normal in 10 patients. For 4 patients with normal visual field, the changes in the mfVEP were of significance. The delay in recordable responses from affected eyes ranged from 2.56 to 18.28 ms (interocular analysis) and 0.1 to 21.86 ms (monocular analysis). Ten patients whose tumor was totally removed showed a recovery of the visual field and mfVEP to various degrees. Visual field of 6 patients showed within normal limits after total removal of the tumor, and the defects of mfVEP in 3 patients remained apparent, while the mfVEP of the other 3 patients showed a complete recovery. Various orbital tumors can cause compressive optic neuropathy. Compressive optic neuropathy secondary to orbital tumors results in mfVEP amplitude reduction and latency prolongation. The changes in measures of mfVEP due to orbital tumors are consistent with the visual field changes in most patients. In some patients, the subjective visual field results and objective mfVEP are discordant. The objective changes of mfVEP may appear earlier than the defect of visual field, and thus it may be able to identify subtle defects that are undetectable with Humphrey perimetry. Postoperatively, recovery of the mfVEP may be later than that of visual field in some patients. The mfVEP changes may assist in both early diagnosis and follow-up of the compressive optic neuropathy secondary to orbital tumors.

MRI and visual-evoked potentials in partners of multiple sclerosis patients

Some epidemiological evidence, particularly concerning the role of Epstein Barr Virus implies that multiple sclerosis (MS) may be transmissible and if correct, this might be revealed by increased prevalence of MS in cohabiting partners. We addressed this problem by neurological assessment, visual-evoked potentials (VEP) and magnetic resonance imaging (MRI) in 112 partners of patients with MS in comparison to a control group of 93 individuals with clinically non-significant head or neck pain and in comparison to UK prevalence. We found one instance of conjugal definite MS. Including this case, VEP were abnormal in five instances with either significant delay (n = 3) or increased interocular latency difference (IOLD) (n = 2) in partners of MS patients thus raising the possibility of subclinical optic nerve demyelination. The mean absolute value of IOLD in partners was greater than the value in controls (P = 0.033). There were no significant differences in MRI findings between the two groups. The finding of one conjugal pair and abnormal VEP in a further four MS partners could have several explanations. It is compatible with the concept of a transmissible agent, although our observations could be due to several biases as well as the play of chance alone.

Pulfrich’s phenomenon in optic nerve hypoplasia

Optic nerve hypoplasia (ONH) is a congenital deficiency of retinal ganglion cells and their axons that form the optic nerve. The condition is associated with visual deficits ranging from no light perception in severe cases, to vision within normal range in mild cases of ONH. We report here a case of mild ONH with normal vision and with visual symptoms relating to a spontaneously occurring Pulfrich effect. A twelve-year-old girl presented with typical visual symptoms (veering to the right when walking, bumping into things) associated with the spontaneous Pulfrich effect. When asked to follow a bob suspended from a simple rigid pendulum swinging in the frontal plane, a clockwise ellipse was reported, indicative of a left-sided Pulfrich effect. This effect was neutralised by an 85% transmission ophthalmic tint placed before the right eye. The inter-ocular latency difference responsible for the illusion was calculated to be 0.88 +/- 0.55 ms. Fundus biometry showed an asymmetry in R and L optic nerve dimensions, the left being smaller than the right. Vision was normal in each eye, as were visual fields, colour vision and stereopsis. The affected eye showed normal flash and pattern VEPs and ERGs, except for a borderline reduction of the pattern ERG (PERG) to very small checks. A case of mild ONH with normal visual function in each eye resulted in a small inter-ocular delay associated with errors in visual perception consistent with a spontaneous Pulfrich effect. Wearing a pair of glasses with the right lens tinted eliminated these difficulties.

Estudo normativo do potencial evocado visual por padrão reverso

OBJETIVOS: Realizar normatização do PEV-PR e analisar influência de, técnica, ângulo visual (AV), e variáveis biológicas, sexo, idade e diferença interocular. METODOLOGIA: 60 voluntários saudáveis divididos em sexo e idade (entre 20-61 anos) foram submetidos a PEV-PR, em cada olho, utilizando dois AV, 14 e 28 min. Foram avaliadas latências das ondas N75, P100 e N120. RESULTADOS:Valor médio de latência (ms) com AV de 14 e 28 min foi respectivamente: 78,2 e 74,3 (N75); 102,3 e 98,8 (P100); 136,7 e 130,5 (N120). Valor N75 foi igual nos dois sexos; P100 maior em homens que em mulheres apenas para AV de 14 min, e N120 maior em homens nos dois tamanhos de AV. Idade e a diferença interocular não mostraram diferenças significativas. CONCLUSÕES:Neste estudo foram observados valores maiores de latência do PEV-PR com AV de 14 min do que 28 min, sendo que o sexo masculino apresentou valores maiores em apenas algumas latências e AV.