Normative values of visual evoked potential in adults.

Background: The aim was to compare the retinal nerve fibre layer (RNFL) thickness and visual evoked potentials (VEP) among eyes with multiple sclerosis (MS)‐associated optic neuritis, unaffected eyes of the same patients and eyes of disease‐free controls. Changes in RNFL thickness, visual acuity (VA) and VEP over time are evaluated in MS‐associated optic neuritis.Methods: Forty‐six eyes of 23 patients (six male and 17 female), who suffer from MS and were diagnosed with unilateral or bilateral optic neuritis, participated in the study. Forty eyes of 20 age‐ and gender‐matched controls were tested. VA measurement, optical coherence tomography and VEP were performed in all patients at presentation and at one, three and six months thereafter.Results: There was a statistically significant difference in VA between MS eyes with optic neuritis and controls (p < 0.0001), as well as between MS eyes with and without optic neuritis (p < 0.005). VA improved over time. Average RNFL thickness was reduced in MS eyes with or without optic neuritis in comparison to control eyes. This reduction in RNFL thickness was more marked over time. The amplitude of P100 was significantly decreased in MS eyes with optic neuritis in comparison to controls (p < 0.0001) and there was a statistically significant delay in peak time of P100 in MS eyes with optic neuritis versus the eyes of normal subjects (p < 0.0001), which improved over time.Conclusion: The present study suggests that there is a progressive decrease in RNFL over time in eyes with optic neuritis associated with MS. The amplitude and latency of P100 in VEP examination returned to normal ranges over time.

Introduction In order to provide the theoretical basis and practical guidance of eye protection during the prone spinal surgery under the general anesthesia, visual evoked potential (VEP) was monitored before and after surgery. Patients and Methods A total of 82 patients were involved in our study and grouped into three groups, S, M, and L groups, respectively, according to the operation time. The P100's latency and amplitude changes and the visual function of preoperative, postanesthetic, and postoperative spots were analyzed to understand their relationship. Results (1) The waveforms of VEP in 78 cases were monitored stably and repeatedly and the other four cases failed. (2) Difference of P100's latency and amplitude at preoperative, postanesthetic time was not statistically significant in all groups. (3) Postoperatively, difference of P100's latency was statistically significant in M and L groups, and no statistically significant difference was observed in S and M groups. Difference in P100's amplitude was statistically significant in all groups. (4) Recovery time of P100's latency has statistically significant differences in all three groups. (5) Two patients in the L group had conjunctival edema, pupillary light reflex obstacles, and visual acuity descending. After receiving positive symptomatic treatment, symptoms disappeared and vision recovered. Conclusion VEP can provide the stable and on-time electrophysiological conductive evidence needed to judge the optical pathway function. The operator should pay close attention to the change in VEP and visual performance if prone spinal surgery continues for more than 4 hours.

Influence of Cataract Surgery on Optical Coherence Tomography and Neurophysiology Measurements in Patients With Retinitis Pigmentosa

Objective: To examine the association of visual evoked potential (VEP) latency and high-contrast visual acuity (VA) with cognitive function in MS patients using a standardized computerized battery. Background Cognition and vision are now recognized as important domains for clinical trials assessment in MS. The correlation of VEP conduction delay and VA with cognitive impairment has not been described. Design/Methods: Participants received a VEP evaluation as well as a Snellen vision test and completed a standardized, validated MindStreams battery designed to detect mild impairment (NeuroTrax Corp., NY) in their primary language. VEP latency categories were: normal =113 and =130 and =150 and 170 msec. Results: Among MS patients (n=435, 870 eyes), Accounting for age, disease duration, and within-patient, inter-eye correlations, abnormal VEP latency was associated with poorer overall battery performance (Global Cognitive Score, p Conclusions: Abnormal VEP latency and high-contrast VA in patients with MS may be associated with reduced cognitive function, particularly in domains related to executive function. Longer VEP latency may be particularly related to poorer visual spatial processing. Further studies will examine the role of afferent visual dysfunction and retinal axonal and neuronal loss in the relation of VEP latency to cognitive impairment and work disability in MS cohorts. Disclosure: Dr. Chahin has nothing to disclose. Dr. Balcer has received personal compensation for activities with Biogen Idec, Vaccinex and Bayer as a consultant and has received honoraria from Biogen Idec and Novartis. Dr. Zarif has received personal compensation for activities with Biogen Idec as a consultant. Ms. Bumstead has received personal compenstion for activities with Biogen Idec and Teva Neuroscience as a consultant. Dr. Fafard has nothing to disclose. Dr. Mebrahtu has nothing to disclose. Dr. Galetta has received personal compensation for activities with Biogen Idec Teva, and Novartis as a speaker.Dr. Galetta has received research support from Biogen Idec. Dr. Doniger has received personal compensation for activities with NeuroTrax Corporation as an employee. Dr. Gudesblatt has received personal compensation for activities with Biogen Idec, Teva Neuroscience, Lundbeck Research USA, Inc. and Medtronic as a consultant.

2. Visual evoked potentials in the diagnosis of multiple sclerosis

Due to the proximity of craniopharyngioma to the optic apparatus, one of the most common complications after surgery is visual deterioration. Intraoperative visual evoked potential (VEP), as a means of real-time visual function monitoring, has been integrated into transsphenoidal surgery for pituitary adenoma to predict postoperative visual outcome. Compared with pituitary tumor, craniopharyngioma often adheres to optic nerves, with increased risk of postoperative visual impairment. Furthermore, extended endoscopic endonasal surgery (EEES) can provide direct visualization of the surgical plane between the craniopharyngioma and the optic nerves, which contributes to analysis of the mechanism of real-time VEP changes during surgery. Therefore, VEP monitoring applied during EEES for craniopharyngioma may have more clinical value. However, only 9 patients who underwent EEES with VEP monitoring for craniopharyngioma have been sporadically reported to date. In this paper, the authors present the largest series to date analyzing the clinical value of VEP to predict postoperative visual outcome in adult patients with craniopharyngioma. Sixty-five adult patients who underwent EEES with intraoperative VEP monitoring for primary craniopharyngioma were retrospectively reviewed. The association between changes in VEP amplitude and postoperative visual outcome was determined. In addition, other potential prognostic factors with regard to postoperative visual outcomes were included in the analysis. Gross-total resection was achieved in 59 patients (90.8%). Reproducible and stable VEP was recorded in 128 of 130 eyes (98.5%). During surgery, VEP remained stable in 108 eyes, 10 (9.3%) of which had new visual acuity (VA) and/or visual field (VF) defects after surgery. Transient VEP decrease was recorded in 15 eyes, 4 (26.7%) of which had visual deterioration. Of the 5 eyes with permanent VEP decrease, 3 (60%) experienced postoperative visual impairment. Permanent VEP decrease (OR 19.868, p = 0.007) and tight adhesion (OR 6.104, p = 0.040) were independent adverse factors for postoperative VA deterioration. Tight adhesion (OR 7.150, p = 0.002) and larger tumor volume (OR 1.066, p = 0.001) were significant risk factors for postoperative VF defects. Intraoperative VEP monitoring can serve as a real-time warning to guide surgeons to avoid postoperative visual impairment. It effectively predicted VA changes in adult patients with craniopharyngioma after EEES. Tight adhesion and larger tumor volume were also strong predictors of postoperative visual impairment.

To investigate the response properties of the electrically evoked potentials (EEPs) elicited by intraorbital optic nerve stimulation with penetrating electrodes using different stimulus parameters. Visually evoked potentials (VEPs) were recorded as a control and for comparative purposes. Teflon-coated tungsten wire electrodes (100 microm core-diameter, 300 microm exposed tip) were inserted intraorbitally into the optic nerve. A charge-balanced biphasic current was delivered to the optic nerve via inserted wire electrodes in 26 anaesthetized rabbits. EEPs were recorded by epidural electrodes placed over the visual cortex. The charge density threshold for eliciting EEPs was determined. Stimulus pulse amplitude, duration, frequency and waveform were varied to study their effects on EEPs. After the experiments, the stimulated optic nerves were examined histologically for examination of implantation position of the stimulating electrode into the optic nerve tissue. EEPs were successfully elicited by intraorbital optic nerve stimulation with penetrating electrodes. The measured amplitude of the first large positive peak (P1) was smaller and the latency of P1 was shorter compared with VEPs. The measured charge density threshold to elicit EEPs was 21.36 +/- 5.64 microC/cm(2). The amplitude of P1 increased and the latency of P1 decreased with increasing pulse amplitude of fixed duration stimuli. The amplitude of P1 increased with increasing pulse duration of fixed amplitude stimuli. For fixed charge stimuli, the amplitude of P1 decreased and the latency of P1 increased as the pulse duration increased. As frequency of stimuli varied from 1 to 10 Hz, the amplitude of P1 decreased monotonically. Among the different charge-balanced biphasic pulse stimulating waveforms, the symmetrical cathode-first biphasic pulse elicited the largest amplitude of P1. Our study demonstrates that intraorbital optic nerve stimulation with different stimulus parameters by penetrating electrodes can evoke cortical responses with different properties. The short-duration symmetrical cathode-first biphasic pulses of current with low frequencies are more efficacious in eliciting electrophysiological responses in the visual cortex than other stimulating waveforms.

The purpose of the present study is to investigate longitudinal changes in Visual evoked potential (VEP) parameters as an objective test after transsphenoidal surgery, its correlation with subjective tests and clinical value of VEP in the prediction of visual outcome. Fifty patients with pituitary macroadenoma who underwent surgical removal of the tumor recruited in this study. All the patients underwent ophthalmic examination, static automated perimetry (SAP), VEP and magnetic resonance imaging (MRI) preoperatively and 3months after surgery. Fifty patients with pituitary macroadenoma (size: 25.1 ± 9.9mm) were recruited in the study. Before surgery, the pattern of VEP showed a prolonged latency with reduced amplitude in eyes with abnormal visual acuity or abnormal visual field. The P100 wave latencies and amplitudes showed significant correlation with visual acuity and SAP scores. After surgery, visual acuity and visual field improvements were seen in 51% and 65.6% of eyes, respectively. Mean SAP and visual acuity scores increased significantly (p < 0.01), P100 wave latency declined and amplitude improved after surgery but not significantly. The mean age of patients, size of tumors and preoperative P100 wave latency were significantly lower in eyes with visual field and acuity improvement. VEP is a helpful quantitative and objective complementary test to visual acuity and SAP exams for assessing pre-operative visual abnormalities and post-operative visual outcome in patients with pituitary macroadenoma.

Lymphocytic hypophysitis (LYH) is a rare neuroendocrine disorder characterized by autoimmune inflammation of the pituitary gland. Visual disturbance is one of the most common and serious symptoms of LYH. Most of the visual symptoms in LYH are secondary to compression of the optic chiasm and some reports have described direct inflammatory involvement of the optic pathways. We describe a 30-year-old man with a 9-day history of bilateral blurred vision. Ophthalmic examination demonstrated severely impaired vision without temporal hemianopsia. Hypothyroidism, hypocortisolism, and hypogonadism were detected in laboratory tests. Central diabetes insipidus was diagnosed by a hypertonic saline infusion test. MRI revealed thickening of the pituitary stalk and enlargement of the hypophysis, which was enhanced with gadolinium. High intensity of the posterior lobe was not recognized on T1-weighted images. These findings established a clinical diagnosis of lymphocytic panhypophysitis. Methylprednisolone pulse therapy was introduced and his visual acuity gradually recovered. The anterior pituitary function improved, but desmopressin was still required. Pattern-reversal visual evoked potentials (VEP) have been widely used to detect optic nerve lesions caused by multiple sclerosis and brain tumors. However, there have been no previous reports of their usefulness for LYH. The P100 latency in our case was slightly prolonged and the amplitude was markedly reduced. These findings are similar to ischemic optic neuropathy and other conditions in which axonal damage is prominent. The prolonged latency and low amplitude on VEP examination in this case showed rapid improvement in parallel with the recovery of visual acuity. Taken together, our case implies the usefulness of pattern-reversal VEP for the diagnosis of optic neuritis in LYH, especially for the evaluation of its pathogenic mechanisms.

The aims of this study were 1) To evaluate retinal nerve fiber layer (fRNFL) thickness and ganglion cell layer plus inner plexiform layer (GCIPL) thickness at the fovea in eyes affected with traumatic optic neuropathy (TON) compared with contralateral normal eyes, 2) to further evaluate these thicknesses within 3 weeks following trauma (defined as “early TON”), and 3) to investigate the relationship between these retinal layer thicknesses and visual function in TON eyes. Twenty-nine patients with unilateral TON were included. Horizontal and vertical spectral-domain optical coherence tomography (SD-OCT) scans of the fovea were taken in patients with unilateral TON. The main outcome measure was thickness of the entire retina, fRNFL, and GCIPL in eight areas. Thickness of each retinal layer was compared between affected and unaffected eyes. The correlation between the thickness of each retinal layer and visual function parameters, including best corrected visual acuity, color vision, P100 latency, and P100 amplitude in visual evoked potential (VEP), mean deviation (MD) and visual field index (VFI) in Humphrey visual field analysis in TON eyes was analyzed. Thicknesses of the entire retina, fRNFL, and GCIPL in SD-OCT were significantly thinner (3–36%) in all measurement areas of TON eyes compared to those in healthy eyes (all p<0.05). Whereas, only GCIPL in the outer nasal, superior, and inferior areas was significantly thinner (5–10%) in the early TON eyes than that in the control eyes (all p<0.01). A significant correlation was detected between retinal layer thicknesses and visual function parameters including color vision, P100 latency and P100 amplitude in VEP, MD, and VFI (particularly P100 latency, MD, and VFI) (r = -0.70 to 0.84). Among the retinal layers analyzed in this study, GCIPL (particularly in the superior and inferior areas) was most correlated with these five visual function parameters (r = -0.70 to 0.71). Therefore, evaluation of morphological change of each retinal layer using SD-OCT can help in understanding TON pathophysiology and indirectly assessing visual function. Moreover, evaluation of the morphological change of the GCIPL in TON eyes may be useful to assess visual function in patients with early TON.

The effect of spectral filters on VEP and alpha-wave responses

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.

The aim of our work was to evaluate neural conduction in visual pathways in subjects with ocular hypertension and glaucoma. We assessed simultaneous recordings of pattern electroretinograms (PERG) and visual evoked potentials (VEP) in 16 subjects with ocular hypertension (OHT), in 16 subjects with primary open-angle glaucoma (POAG) and in 15 age-matched controls. The visual stimuli were checkerboard patterns (the check edges subtend 15 min of visual arc; contrast 70%) reversed at the rate of 2 reversals/s. In OHT and POAG patients we found PERG and VEP latencies significantly longer than in controls. The P50-N95 PERG amplitudes were significantly reduced in OHT and POAG eyes. VEP amplitudes were significantly reduced in POAG eyes, while in OHT they were similar to controls. The retinocortical time (RCT; difference between VEP P100 latency and PERG P50 latency) was longer in POAG patients than in controls; no differences between patients with OHT and controls were observed. Moreover, we observed that in POAG the longer RCT was inversely related to the PERG amplitude. Our results suggest that involvement of the innermost retinal layers in POAG is accompanied by slowed neural conduction in the visual pathways.

Changes in visual evoked potentials (VEP) induced by tricyclic antidepressants in patients with endogenous depression were studied.VEP was recorded 3-5 times consecutively before and during the treatment. Drug-induced changes in the amplitude-ratios of P100 of VEP after loading mental tasks as well as the changes in the amplitude and latency of the baseline VEP before the tasks were studied during the treatment with amitriptyline (AMP) or imipramine (IMP).The results were as follows :1) The amplitude-ratios after loading the tasks increased at least once in the course of the treatment with AMP or IMP. The increase reached the level of statistical significance only when the doses of more than 75 mg per day were given.2) With the doses of less than 75 mg per day the amplitude-ratios after the tasks scarcely showed any changes in patients treated with AMP, but showed a slight increase in patients with IMP.3) In cases of continuous high dose administration of the drugs re-decrease of the amplituderatios sometimes occurred. The re-decrease was more often seen in patients treated with AMP than in those with IMP.4) While amplitude of P100 of the baseline VEP before the tasks tended to decrease according to the dose increase in patients treated with AMP, no consistent changes were seen in patients with IMP regardless of the dose. No relationship was observed between P100 latency and the dose in patients treated with AMP, nor in those treated with IMP.From these results, it is inferred that both AMP and IMP simultaneously affected stimulatory and inhibitory processes in depressive patients, and that AMP showed stronger inhibitory effects and IMP stronger stimulatory ones.

Normalisation of the visual evoked potential (VEP) in patients with optic neuritis (ON) appears to be a rare phenomenon. However, although several workers have indicated that it can happen, they have not followed up with subsequent VEP tests to confirm how long the VEP latency of the affected eye remains in the normal range. To resolve this, 18 patients with a clinical diagnosis of acute unilateral ON were followed for 5 years with repeated VEP tests to determine if the latency of the P2 wave from affected eye could return to the normal range. Furthermore, in cases where the latency returned to normal, the length of time that it remained so was also assessed. The normal range for the latency of the P2 wave was determined by measuring VEPs from a group of 18 healthy control subjects with a similar age distribution to the patients. This established an upper limit of 115.9 ms. At presentation the mean P2 latency of the affected eyes of the patients was 140 ms with a standard deviation of 16 ms. In general, the VEP latencies remained constant over the period of the investigation. However two patients demonstrated a return to normal latencies but this was only temporary. Their latencies become prolonged again within 2 years. These results provide evidence that the delayed P2 latency observed in patients with ON can return to the normal range in a small percentage of cases. However, this improvement may spontaneously deteriorateonce more as a result of further episodes of subacute demyelination.