Electrophysiological discrimination between retinal and optic nerve disorders

In this study we show how the Pattern ERG (PERG) can be used to distinguish between optic nerve and retinal disease. Records from eyes with RBN and delayed visual evoked responses are compared with those recorded from the normal fellow eyes. In optic nerve disease there is a selective reduction of the later negative component of the PERG. PERGs were also recorded from patients with mild diabetic retinopathy. These were divided into three groups on the basis of the delay in their Visual Evoked Potential (VEP). The amplitude of both positive and negative components of the PERG fall with increasing severity of the disease thus showing that the abnormally long delay in VEP found in some cases is due to retinal disease rather than optic nerve disease.     

Pattern electroretinography (PERG) and an integrated approach to visual pathway diagnosis

The pattern electroretinogram (PERG) provides an objective measure of central retinal function, and has become an important element of the author's clinical visual electrophysiological practice. The PERG contains two main components, a positivity at approximately 50ms (P50) and a larger negativity at approximately 95ms (N95). The P50 component is affected by macular dysfunction with concomitant reduction in N95. The PERG therefore complements the Ganzfeld ERG in the assessment of patients with retinal disease. In contrast, the ganglion cell origins of the N95 component allow electrophysiological evaluation of ganglion cell function both in primary disease and in dysfunction secondary to optic nerve disease, where selective loss of N95 can be observed. Both macular dysfunction and optic nerve disease can give abnormalities in the visual evoked cortical potential (VEP), and the PERG thus facilitates more meaningful VEP interpretation. This review addresses the origins and recording of the PERG, and then draws on extensive clinical data from patients with genetically determined retinal and macular dystrophies, other retinal diseases and a variety of optic nerve disorders, to present an integrated approach to diagnosis.     

Pattern electroretinogram plus visual evoked potential: A decisive test in patients suspected of malingering

Along the processing chain in the visual pathway the pattern electroretinogram (PERG) is a better indicator of the peripheral function than the visual evoked potential (VEP). Therefore the PERG and the VEP will be impaired equally by disturbances before the ganglion cell layer (e.g., blurred image or retinal disease) and differently by further centrally located diseases (e.g., tumor compression of the optic nerve). Thus in patients complaining of reduced visual acuity who show disturbed VEP but a normal PERG, malingering can be definitely ruled out. Representative combinations of PERG and VEP findings are described.     

Electrophysiological assessment of optic nerve disease

The electrophysiological findings in optic nerve and primary ganglion cell dysfunction are reviewed. The value of the pattern reversal visual-evoked potential (VEP) in the diagnosis of optic nerve disease, and the pattern appearance VEP in the demonstration of the intracranial misrouting associated with albinism, are discussed. The pattern electroretinogram (PERG) is used in the direct assessment of ganglion cell function. The use of PERG or multifocal electroretinography (mfERG), to enable the distinction between VEP delay due to optic nerve disease and that due to macular dysfunction, is described.     

Electrophysiological discrimination between retinal and optic nerve disorders

In this study we show how the Pattern ERG (PERG) can be used to distinguish between optic nerve and retinal disease. Records from eyes with RBN and delayed visual evoked responses are compared with those recorded from the normal fellow eyes. In optic nerve disease there is a selective reduction of the later negative component of the response. PERG's were also recorded from patients with mild diabetic retinopathy. These were divided into three groups on the basis of the delay in their Visual Evoked Potential (VEP). The amplitude of both positive and negative components fall with increasing severity of the disease thus showing that the abnormally long delau in VEP found in some cases is due to retinal disease rather than optic nerve disease.     

Electrophysiological monitoring in a patient with an optic nerve glioma

Purpose To report a case illustrating the value of pattern VEP and pattern ERG (PERG) in monitoring optic nerve gliomata (OG). Case report A 15-year-old girl presented with a 3-year history of frontal headaches and a 5-month history of blurred vision in the right eye. MRI scanning revealed a thickened, right optic nerve extending to the cranial opening of the optic canal, consistent with an optic nerve glioma. Pattern VEP showed a mildly delayed major positive component consistent with optic nerve dysfunction. The PERG N95:P50 ratio was subnormal in keeping with retinal ganglion cell involvement. Visual acuity decreased over the following 2 years and repeat VEP objectively demonstrated marked deterioration in optic nerve function despite neuroradiology showing no significant change in the tumour. Conclusions Pattern VEPs and pattern ERGs can provide early objective evidence of optic nerve/retinal ganglion cell dysfunction in optic nerve gliomata. Serial recordings can objectively demonstrate worsening function in the absence of significant neuroradiological change.     

The pattern electroretinogram in optic nerve disease

Pattern evoked electroretinograms (PERG), diffuse flash electroretinograms (ERG) and visual evoked potentials were studied in patients with unilateral optic nerve disease. Patients with Snellen acuities of less than 6/30 did not have recordable PERGs in their affected eye, whereas their diffuse flash ERGs were normal. The VEPs were correspondingly reduced or absent when recorded from the poorer seeing eyes. A second group of patients with Snellen acuity between 6/6 and 6/30 in the involved eye showed reductions in the mean PERG amplitude of the affected as compared with the normal eyes. All affected eyes showed an abnormal contrast threshold measured with the PERG amplitude. Such results underscore the diagnostic value of the PERG in detecting even mildly affected cases of optic nerve disease.     

Effect of decreased retinal illumination on simultaneously recorded pattern electroretinograms and visual-evoked potentials

Sixteen normal subjects and three patients with optic neuritis were studied to determine the effect of decreased retinal illumination on simultaneously recorded pattern electroretinograms (PERG) and visual-evoked potentials (VEP). Using neutral-density filters (NDF), it was found that linear modeling is an excellent fit for VEP/PERG amplitudes and latencies as log functions of retinal illumination, both for individual eyes and averages of pooled data. Within narrow statistical limits, regression slopes show that mean PERG B-wave and VEP P100 latencies are affected almost identically by decreased illumination, leaving the mean retinocortical time (RCT) virtually unchanged. However, mean B-wave amplitude was greatly reduced at retinal illuminations at which P100 amplitude was unaffected. Of clinical significance was that these latency and amplitude effects were found in each eye tested, whether normal or pathologic. In particular, the RCT in normal subjects was never found to be statistically abnormal due to decreased retinal illumination, and it faithfully represented the optic nerve lesion in the patients with optic neuritis. This result was applied to a population of eight patients with uncomplicated cataracts. The significance of these results is discussed.     

Electrophysiological assessment of aphakic cystoid macular oedema.

Focal electroretinograms (FERG), pattern electroretinograms (PERG), and visual evoked potentials (VEP) were studied in a group of 30 aphakic patients with cystoid macular oedema (ACME). When compared with a control group of age-matched aphakics, 35% of patients were found to have abnormal FERG responses and 53%--over half of whom had normal FERG responses--showed abnormal PERG amplitudes. Although most of the patients had associated optic disc leakage, VEP latencies were normal in 26 out of 30. These results may explain the more severe visual loss seen in some ACME patients where the ophthalmologically visible retinal changes do not seem sufficient to explain such reduction in vision.     

VEP and PERG in patients with multiple sclerosis,with and without a history of optic neuritis

Purpose

Visual electrophysiology is routinely used to detect the visual complications of multiple sclerosis, but the analysis mostly focuses on visual evoked potential (VEP) and especially the P100 component. Our goal was to analyze the components and waveform alterations of VEPs and pattern electroretinograms (PERGs) in patients with multiple sclerosis (MS) with good vision.

Methods

The main VEP and PERG components of 85 patients with MS were analyzed in two groups: 38 patients who had optic neuritis in their history (ON group) and 47 patients who had never had optic neuritis (MS group). The results were compared against a control group of 47 healthy subjects.

Results

Both VEP and PERG alterations occurred in a greater number of patients than expected, and these alterations were not necessarily linked to ON in the history or a deterioration of visual acuity.

Conclusions

Both VEP and PERG can detect dysfunction in the visual system in MS, even if the patient has no subjective symptoms. Even if PERG is not routinely used in neuro-ophthalmology, the results suggest that PERG assessment may provide useful information describing the retinal defect in MS.

     

Correlation between morphological and functional retinal impairment in multiple sclerosis patients.

PURPOSE: To assess whether a correlation exists between optic nerve fiber layer (NFL) thickness and the retinal or visual pathway function in multiple sclerosis (MS) patients previously affected by optic neuritis. METHODS: Fourteen patients with a diagnosis of definite MS were examined. All had been affected by optic neuritis (MSON) with complete recovery of visual acuity (14 eyes included in study). These were compared with 14 eyes from 14 age-matched control subjects. NFL thickness was measured by optical coherence tomography (OCT). Three different measurements in each quadrant (superior, inferior, nasal, and temporal) were taken and averaged. The data in all quadrants (12 values averaged) were identified as NFL Overall, whereas the data obtained in the temporal quadrant only (3 values averaged) were identified as NFL Temporal. Retinal and visual pathway function was assessed by simultaneously recording pattern electroretinograms (PERGs) and visual evoked potentials (VEPs) using high-contrast (80%) checkerboard stimuli subtending 15 minutes and 60 minutes of the visual arc (min arc) and reversed at the rate of two reversals per second. RESULTS: In MSON eyes there was a significant (P < 0.01) reduction in NFL thickness in both NFL Overall and NFL Temporal evaluations compared with the values observed in control eyes. PERG, (15-min arc checks) and VEP (15-min arc and 60-min arc checks), showed a significant (P < 0.01) delay in latency and reduction in amplitude. NFL Overall and NFL Temporal values were significantly correlated (P < 0.01) to the PERG P50 latency and P50 to N95 amplitude recorded with 15-min arc checks. No correlations (P > 0.01) between NFL values and the other electrophysiological data (PERG recorded with 60-min arc checks and VEP recorded with 15-min arc and 60-min arc checks) were found. CONCLUSIONS: There is a correlation between PERG changes and NFL thickness in MS patients previously affected by optic neuritis, but there is no correlation between VEP changes and NFL thickness.     

Retinal origin of VECP delays as revealed by simultaneously recorded ERG to patterned stimuli

Electroretinal and electrocortical potentials evoked by reversing checkerboards (PERG, PVECP) were simultaneously recorded in diseases of the central retina (10 patients) and in tumor-related optic nerve disorders (11 patients) exhibiting comparable P-100 delays in the PVECP. Retinal diseases showed a peak-time delay both in the PERG and in the PVECP, while optic nerve disorders revealed no delay in the PERG. Thus, simultaneous recording of PERG and PVECP may differentiate retinal from postretinal disorders of the visual system. The method also may provide information about the site of an underlying disorder in cases of visual disturbance without obvious changes of the ocular fundus.Presented at the 26th ISCEV Symposium, Estoril, Portugal, 21–25 May 1988.     

Clinical electrophysiology of the optic nerve and retinal ganglion cells

Clinical electrophysiological assessment of optic nerve and retinal ganglion cell function can be performed using the Pattern Electroretinogram (PERG), Visual Evoked Potential (VEP) and the Photopic Negative Response (PhNR) amongst other more specialised techniques. In this review, we describe these electrophysiological techniques and their application in diseases affecting the optic nerve and retinal ganglion cells with the exception of glaucoma. The disease groups discussed include hereditary, compressive, toxic/nutritional, traumatic, vascular, inflammatory and intracranial causes for optic nerve or retinal ganglion cell dysfunction. The benefits of objective, electrophysiological measurement of the retinal ganglion cells and optic nerve are discussed, as are their applications in clinical diagnosis of disease, determining prognosis, monitoring progression and response to novel therapies.Subject terms: Optic nerve diseases, Retina     

视觉诱发电位在视神经挫伤诊断治疗中的应用

目的 探讨视神经挫伤后的视觉诱发电位（ＶＥＰ）的异常率、挫伤程度及预后估计。方法记录单眼挫伤患者的伤眼、对侧眼及治疗后伤眼的视觉诱发电位（ＶＥＰ）。结果 （１） 挫伤眼各视力组ＶＥＰ异常率明显高于对照组,且随挫伤眼视力的下降而增高。（２）挫伤眼矫正视力〈０．１者ＶＥＰ异常更明显,且预后差。结论 ＶＥＰ是视神经 失伤早期诊断、判断预后的客观检查方法。     

Contrast sensitivity and pattern visual evoked potential in patients with glaucoma

Contrast sensitivity and pattern visual evoked potential (VEP) were measured in cases of ocular hypertension and primary open-angle glaucoma at various stages. The visual field of each eye was examined quantitatively and the retinal nerve fiber layer and optic disc were precisely assessed with magnified stereoscope fundus photography.This study revealed that contrast sensitivity of the eyes with glaucoma was within the normal range in the very early stage of the disease. As optic nerve damage advanced, high-or low-frequency loss developed. Further optic nerve damage produced a level type of loss.Pattern VEPs also showed increasing abnormalities as glaucomatous optic nerve damage progressed. Measurements of contrast sensitivity and pattern VEP were found not to be as sensitive as quantified precise visual field measurment or color stereosopic fundus photography for detection of minor optic nerve damage in cases of early glaucoma. These methods may be useful, however, as an objective and subjective monitor of progression of optic nerve damage in glaucoma.     

Visual function correlates with nerve fiber layer thickness in eyes affected by ocular hypertension.

PURPOSE: To test whether the high variability observed when measuring pattern electroretinogram (PERG), visual evoked potentials (VEP), and spatial contrast sensitivity (SCS) in eyes with ocular hypertension is associated with variation in nerve fiber layer thickness, as measured by optical coherence tomography (OCT). METHODS: The study involved 32 untreated eyes (32 patients; age range, 29-64 years) showing a normal whiteon-white 24/2 Humphrey (San Leandro, CA) perimetry, IOP between 23 and 28 mm Hg, best corrected acuity of 20/20 or better, and none of the following papillary signs on conventional color stereo slides: rim notch(es), peripapillary splinter hemorrhages, or increased vertical-to-horizontal cup-to-disc ratio. On recruitment, each eye underwent SCS testing, OCT, PERG, and VEP recordings. Linear regression (Pearson's test) or Spearman's rank regression was adopted for the analysis of the data. RESULTS: The 95% confidence limits of the electrophysiological data were: PERG P50 latency, 59.3 to 63 msec; PERG P50 to N95 amplitude, 0.74 to 1.15 cmV; VEP P100 latency, 113 to 118 msec; VEP N75 to P100 amplitude, 3.81 to 4.90 micromV. The 360 degrees nerve fiber layer thickness overall (NFLO) ranged between 113 and 169 microm (145+/-16 microm; mean+/-SD) and significantly correlated with PERG P50 to N95 amplitude (r: 0.518; P = 0.002), PERG P50 latency (r: -0.470; P = 0.007), VEP N75 to P100 amplitude (r: 0.460; P = 0.008), VEP P100 latency (r = -0.422; P = 0.016) and SCS at 3 cyc/deg (r: -0.358; P = 0.044). CONCLUSIONS: The variability of PERG, VEP, and SCS testing observed in eyes with ocular hypertension is associated with differences in NFL thickness (the thinner the layer, the worse the visual function).     

Visual evoked potentials in chessboard pattern reversion in children with optic neuritis]

Visual evoked potentials (VEP) to chess pattern reversion were studied in 17 children with optic neurites during the acute stage and in the course of convalescence 1-2 months and 1-3 years after the disease onset. Coarse VEP changes were detected in the patients during the acute stage of optic neuritis. A positive time course of VEP was followed up in late periods after the acute attack of the disease. Despite normalization of vision acuity, no complete restoration of VEP to small-cell chess patterns was seen. The findings evidence that studies of VEP to chess pattern reversion should be carried out to detect subclinical involvement of the optic nerve and to timely diagnose optic neuritis in children.     

视觉诱发电位在眼科学中的临床应用价值——Christchurch医院的经验

目的 探讨视觉诱发电位在眼科临床中的应用价值.方法 总结Christchurch医院30年来视觉诱发电位在临床应用的经验.结果 视神经炎是视神经的炎症病变,表现为单眼的突发性失明并伴随眼球移动时疼痛.视神经炎的电生理表现为视觉诱发电位的潜伏期延长,这种延长在发病3周视力恢复后仍存在.由于视神经炎关系到多发性硬化症的并发,对其正确的鉴别诊断十分重要.视神经诱发电位一个重要的临床应用,是能发现已痊愈的视神经炎的电位异常.在视觉诱发电位中,P100潜伏期的延长可从急性期延迟很长时间,它在占位性视神经疾病的诊断中有重要的诊断价值,也可作为视交叉占位性病变的确诊手段.另外,视觉诱发电位在功能性失明或装盲(尤其是儿童)有重要应用价值.结论 视觉电生理在眼科临床中的应用应得到肯定.(中国眼耳鼻喉科杂志,2007,775～78)     

Monitoring glaucoma progression with visual evoked potentials of the blue-sensitive pathway

PURPOSE: To determine the value of visual evoked potentials with blue-on-yellow pattern stimulation in follow-up of glaucoma. METHODS: This prospective longitudinal concurrent study included a heterogeneous cohort of two groups, perimetric (n = 161) and preperimetric (n = 118), of patients with chronic open-angle glaucoma and 113 healthy control subjects. In the preperimetric glaucoma group, patients showed glaucomatous abnormalities of the optic disc, maximum intraocular pressure higher than 21 mm Hg, and unremarkable computerized visual field examination results. Patients underwent up to three VEP measurements with blue-on-yellow pattern stimulation, as well as qualitative and morphometric evaluation of color stereo optic disc photographs. Mean follow-up time between measurements was 24 months. VEP measurements were separately analyzed in preperimetric subjects, with and without progression of optic nerve damage. Progression of glaucoma was defined as increasing loss of neuroretinal rim. RESULTS: A separate analysis of VEP peak times in patients in the preperimetric group, with and without progression of glaucomatous optic nerve damage, showed no significant difference at baseline but a significant prolongation (P = 0.01) in patients with progressive disease, 2 years before morphologic changes were evident. VEPs in patients with nonprogressive disease were statistically unchanged during the observation period. The perimetric group and both preperimetric groups showed significantly prolonged VEP peak times in comparison with the control group (P < 0.001). CONCLUSIONS: In addition to photographic evaluation to detect glaucomatous disc atrophy, the blue-on-yellow VEP may be an objective electrophysiological tool for monitoring patients with glaucoma, because peak times are significantly associated with progression of optic nerve damage.     

视神经挫伤60例的视觉诱发电位分析

目的:探讨视觉诱发电位(visual evoked potential,VEP)对视神经挫伤临床诊断的作用。方法:对我科近两年临床诊断为视神经挫伤的患者60例(72眼)进行VEP检查。结果:P-VEP正常30眼;P100波潜伏时延迟22眼;P-VEP无波,F-VEP振幅降低12眼;P-VEP、F-VEP均无波8眼。结论:VEP检查是视神经挫伤的客观检查手段之一。