Retinal oscillatory potentials recorded by dermal electrodes

Dermal electrodes allowed the recording of retinal oscillatory potentials with similar shape and timing as tracings obtained with convential corneal electrodes. Normative data is presented. We concluded that dermal electrodes were a reproducible and more comfortable method of testing.The results were presented in part at the XXIV I.S.C.E.V. Symposium, Palermo (Italy), May 10–15, 1986.     

Basic research and clinical aspects of the oscillatory potentials of the electroretinogram

This paper reviews current knowledge concerning the oscillatory potentials (OPs) of the electroretinogram (ERG). The first section describes the basic characteristics of the OPs primarily studied in healthy subjects. The behavior of the OPs is different from the a- and b-waves, indicating separate mechanisms for generation of the OPs compared with the major components of the ERG. The second section deals with the present view of the origin of the OPs collected from experimental studies of the vertebrate retina, including the primate. Findings favor the conclusion that the bipolar (or interplexiform) cells are the probable generators of the OPs. The third section gives clinical examples of the sensitivity of OPs to early disturbances of retinal function in different eye diseases.     

Effects of intravenous L-acetylcarnitine on retinal oscillatory potentials

L-acetylcarnitine is a compound with cholinergic properties and putative action on the visual system and the glucose metabolism. Ten healthy, emmertropic volunteers (age range: 21 to 28 years) were studied. Each subject was administered 5, 10, and 30 mg/kg acute intravenous doses of L-acetylcarnitine and matching placebo. Retinal oscillatory potentials to full-field flash stimulation were recorded before and 30, 60, and 120 min after administration. A systematic reduction of the implicit time of the P2 and N2 oscillatory potential components was observed after administration of the 10 and 30 mg/kg doses: significant changes were not evident at the 5 mg dose or after placebo. The latency reduction was significantly correlated with the postdrug increment of the L-acetylcarnitine plasma concentration. No other systematic modification in latency of amplitude was observed.The results were presented in part at the XXV I.S.C.E.V. Symposium, Sarasota (Florida), April 26–30, 1987.     

Variability in clinically measured photopic oscillatory potentials

Oscillatory potentials found on the ascending phase of the electroretinogram b-wave probably originate in some element(s) of the inner plexiform layer. As oscillatory potentials are particularly sensitive to changes in retinal, and possibly choroidal, blood flow, they have been used extensively to provide clinical measures of the degree of retinal ischemia during the progression of diabetic retinopathy. Recent studies in our laboratories have disclosed previously unreported significant variability in the photopic oscillatory potentials on repeated measures even in tightly controlled conditions. The amplitude of five recordable light-adapted wavelets exhibited considerable intra- and inter-subject variability. Until further investigation can determine factors affecting standardization of testing, it appears that changes in oscillatory potential implicit times rather than in amplitudes are a better measurement in clinical neurophysiology.     

视网膜脱离复位后的振荡电位观察

目的：应用视觉电生理技术观察孔源性视网膜脱离复位术后的振荡电位变化，了解术后视网膜的微循环改善情况。方法：选用美国LKC公司UTAS－E2000型电生理仪，按照国际标准化建议对73例孔源性视网膜脱离患者在巩膜扣带术术前，术后记录振荡电位，术后随访个月。选择43例为对照组。结果：视网膜脱离后，振荡电位振幅明显下降，子波数减少，手术复位后1个月，子波数增加，但振荡电位的总振幅在随访期间无明显变化，仅在术后5个月有缓慢增长趋势。一些病例可在术后远期出现改变。结论：视网膜脱离复位后，其微循环在短期内有一定程度的恢复，与手术方法及视网膜的病理损害有关。     

The effect of iodoacetic acid on the electroretinogram and oscillatory potentials in rabbits

It has been shown that a single injection of iodoacetic acid selectively (but temporarily) abolishes the b-wave of the electroretinogram. We examined whether such use of this chemical further substantiate our claim that the b-wave of the electroretinogram is a composite potential resulting from the summation (or integration) of faster retinal potentials, usually referred to as the oscillatory potentials. Full-field electroretinograms were recorded from adult New Zealand rabbits before and after a single, bolus injection of 15mg/kg of buffered iodoacetic acid. Both the 1–1000 Hz electroretinogram and the 100–1000 Hz oscillatory potentials were recorded simultaneously. The oscillatory potentials considered in this study were those normally seen on the rising phase of the b-wave. Following the intravenous injection of iodoacetic acid, there was a progressive decrease in the amplitude and peak time of the b-wave. This observation also was reflected in the oscillatory potential recordings, in which the long-latency oscillatory potentials (3 and 4) progressively disappeared while oscillatory potential 2 remained. We believe that these findings further support our contention that the oscillatory potentials are major components of the b-wave.     

Retinitis pigmentosa and inner retina. Functional study by means of oscillatory potentials of the electroretinogram

The alterations of the inner retina in retinitis pigmentosa have been described in previous papers less often than the external retina alterations, both from the electrophysio-logical and morphological point of view. The oscillatory potentials (OPs) of the electroretinogram (ERG) are a good tool to investigate the inner part of the retina because of the deep anatomical location of their generators. We studied the photopic OPs in a group of 25 subjects affected with retinitis pigmentosa and compared them with other ERG components to obtain information about the functional damage of the inner retina. The OPs were recordable in 9 patients. No analogies were found with the inheritance modes. No relationship was found between OPs and 20 Hz ERG photopic response which was still present in a consistent number of eyes when OPs were no longer recordable. Such finding can be interpreted as an expression of inner retinal damage paralleling the photoreceptors and retinal pigment epithelium impairment.     

Evaluation of inner retinal function in myopia using oscillatory potentials of the multifocal electroretinogram

PURPOSE: Oscillatory potentials have been suggested to arise from the inner retina at the level of amacrine cells and inner plexiform layer and they are thought to provide a non-invasive assessment of inner retinal function. We sought to investigate the response dynamics of the inner retina of adult emmetropes and myopes by analysing the oscillatory potentials of the multifocal electroretinogram (mfERG) in these groups. METHODS: Eleven emmetropes and 18 myopes underwent mfERG testing using VERIS 5.1.5X. Myopes were further separated based on whether their myopia was stable (n=9) or progressing (n=9). Oscillatory potentials were recorded using a modified mfERG stimulation technique, the slow flash paradigm, and they were extracted using band-pass filtering from 100 to 300 Hz. The slow flash mfERG stimulus array consisted of 103-scaled hexagons and flickered according to a pseudorandom binary m-sequence (2(13)-1). Amplitudes and implicit times of the first-order oscillatory potentials were analysed. RESULTS: There were significant differences in the implicit time of the oscillatory potentials of the emmetropes, stable myopes and progressing myopes (F(2,25)=3.663, p=0.043). Progressing myopes had significantly shorter implicit times compared to emmetropes (p=0.026 by 1.0-4.7 ms) and stable myopes (p=0.043 by 0.8-1.3 ms), whereas implicit times of stable myopes and emmetropes were similar. There were no statistically significant differences in amplitude of the oscillatory potentials between the groups (F(2,25)=0.890, p=0.426). CONCLUSIONS: Significant differences in multifocal oscillatory potentials between stable and progressing myopes were found. This finding is further evidence of an inner retinal involvement in human myopia progression and may suggest an underlying alteration to dopaminergic or GABAergic retinal systems.     

The effect of 2-amino-4-phosphonobutyric acid on the oscillatory potentials of the electroretinogram

Previous reports have shown that an intravitreal injection of 2-amino-4-phosphonobutyric acid, a glutamate analogue that selectively blocks the photoreceptors' input to the on-bipolar cells, produces a rapid decrease in the amplitude of the electroretinographic b-wave. To our knowledge, the effect of this glutamate analogue has not been examined on the oscillatory potentials. We therefore conducted such a study. A needle electrode was inserted into the anterior chamber of the eyes of seven anesthetized and paralyzed rabbits to record simultaneously the electroretinogram and the oscillatory potentials. These responses were evoked by flashes of white light delivered in mesopic conditions. As expected, an injection of 2-amino-4-phosphonobutyric acid, produced a rapid decrease in the amplitude of the b-wave, while the a-wave was relatively spared. The amplitude of the oscillatory potentials also decreased rapidly. At maximal effect, the electroretinogram essentially consisted of a normal a-wave followed by small oscillations and no evidence of a b-wave. The 100–1000 Hz recording confirmed that the oscillations seen on the postinjection electroretinograms were remnants of the original oscillatory potentials.     

Relationships between the electroretinogram a-wave,b-wave and oscillatory potentials and their application to clinical diagnosis

The electroretinogram is the electrical response of the retina to a light stimulus. The amplitude and temporal pattern of its components, the a-wave, the b-wave and the oscillatory potentials, depend on the functional integrity of the retina, on the intensity of test flash reaching the retina and on the ambient illumination. The latter contributions to the normal variability in the electroretinogram can be circumvented by constructing the relationships between the different electroretinogram waves. The electroretinogram responses were recorded from 18 dark-adapted subjects with normal vision. The slope of the a-wave and the amplitude of the b-waves were measured in the time domain. The oscillatory potentials were isolated by a digital filter and were transformed to the frequency domain for quantitative measurement. The relationship between each pair of variables could be fitted by linear segments. Our findings suggest that this mode of electroretinogram analysis can be useful in localizing the site of action of retinal disorders and that the relationship between the a-wave slope and the power density of the oscillatory potentials is a useful index for identifying disorders of the inner retina.     

不同通频带和刺激光强对小鼠视网膜电图OPs波的影响

目的 通过改变不同通频带和不同光强刺激，探讨昆明小鼠、BALB／C、C57BL／6J小鼠视网膜电图OPs检查的最适通频带和最适闪光强度。方法 昆明小鼠、BALB／C、C57BL／6J小鼠各10只，在暗适应条件下，在不同通频带条件下，分别做视网膜振荡电位(OPs)记录，找出小鼠最适通频带，再在此通频带基础上，进行不同光强下视网膜振荡电位(OPs)记录。结果 不同品系的小鼠在不同光强情况下，其振荡电位随着光强的增强其OPs波波形和幅值随之增高，02波的潜伏期逐步缩短，在2．0(标闪)cd／m^2每秒光强条件下较为稳定。其中BALB／C小鼠幅值最小，C57BL／6J小鼠幅值最大。在通频带75～300Hz时，其振荡电位幅值和潜伏期最为稳定。结论 建议在小鼠视觉电生理检查时，其振荡电位的闪光强度应为2．0(标闪)cd／m^2每秒，通频带应为75～300Hz。     

应用视网膜电图评估早产儿视网膜病变退化后的视功能

目的通过闪光视网膜电图（flash electroretinogram,F-ERG）评估曾患早产儿视网膜病变（retinopathy ofprematurity,ROP）但自行消退的患儿的视功能情况,比较其与正常早产儿的异同。方法随机选择胎龄为26~36周,出生体重为990-2700g,曾患早产儿视网膜病变但自行消退的早产儿15例（30只眼）在半岁~2岁进行F-ERG检查,并选择胎龄、出生体重和检查年龄相似的正常早产儿作为对照组,对比F-ERG各波的振幅和潜伏期。结果 ROP组和正常对照组视杆反应b波潜伏期的差异有统计学意义（P〈0.05）,最大混合反应a波、b波,视锥反应a波、b波潜伏期的差异均无统计学意义;视杆反应b波,最大混合反应a波、b波,视锥反应a波、b波振幅及30Hz闪烁光及振荡电位峰值的差异均无统计学意义（P〉0.05）。结论早产儿视网膜病变退化后对患儿的视功能影响不大,因此,发现轻度的早产儿视网膜病变不必急于手术,可以密切观察其能否消退疾病进展再考虑是否手术,视杆细胞功能的损伤可考虑以后行视功能训练。     

Full-field ERG responses recorded with skin electrodes in paediatric patients with retinal dystrophy

Purpose: Assess ERG responses recorded with skin electrodes in children with retinal dystrophies. Method: ERG responses were recorded using skin electrodes in 17 healthy children and 43 paediatric patients with retinal dystrophy. Subjects were aged 4–14years. ERG responses were recorded to full-field stimuli similar to those recommended in the ISCEV standard. The type of retinal dystrophy was classified on the basis of standard clinical criteria and the ERG responses were compared with those of the age-matched controls. Results: ERG responses were abnormal in every patient. The specific type of ERG abnormality was also consistent with the clinical findings in the majority of patients. Rod responses were abnormal in every patient with a rod–cone dystrophy and cone responses were also abnormal in the majority of patients. Those patients with cone dystrophy or rod monochromatism had normal or near normal rod responses but sub-normal or absent cone responses. Patients with CSNB or XLRS had a sub-normal b-wave but normal amplitude a-wave. Conclusion: ERGs can be recorded successfully with skin electrodes in paediatric patients and responses can aid the diagnosis of the type of retinal dystrophy.     

Alteration of monkey retinal oscillatory potentials after MPTP injection

We have investigated the functional role of dopamine in the monkey retina by recording the retinal responses to flash stimulations before and after destruction of dopaminergic cells by intravenous injection of N-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). We evaluated specifically the oscillatory potentials (100 Hz-3KHz) of the electroretinogram. By day 47 after MPTP injection, a selective decrease of the amplitude of the first oscillatory potential was observed. At that time the animals had been receiving antiparkinsonian therapy since day 15. These results suggest that retinal dopaminergic neurons may play a role in the generation of the first oscillatory potential, and moreover, that each oscillatory potential should be considered individually.     

糖尿病视网膜病变振荡电位和荧光血管造影的相关性

目的 :研究在荧光素钠血管造影 (FA)和吲哚青绿血管造影 (ICGA)下糖尿病视网膜病变 (DR)在不同阶段、形态改变时的振荡电位 (OPs) ,了解DR的功能学与形态学改变的特点及其之间的联系。方法 :选择 4 9名糖尿病患者(89只患眼 ) ,按在FA下DR的不同阶段分 4组 (88眼 ) ,按ICGA分 2组 (6 0眼 ) ,选择 4 3只正常眼为对照组 ,对所有眼按国际标准化方法进行OPs检测。结果 :OPs总和振幅在FA有改变时下降 ,OP2 振幅在FA无改变时下降 ,有改变时进一步下降 ;无灌注期与新生血管期的OPs总和振幅及各子波振幅改变相同 ;ICGA晚期 ,部分眼出现晚期弥散性高荧斑和极晚期高荧伴低荧的“椒盐状”外观 ,与此相应 ,OP3 振幅和OP4潜伏期较对照组下降和延长。结论 :OP2 振幅较OPs总和振幅在DR早期诊断方面敏感 ,无灌注期和新生血管期的视网膜循环状态相似 ,无灌注区可与新生血管一样作为DR进展的质变标志 ,ICGA后期改变与OPs的指标有一定联系     

A comparison of oscillatory potential and pattern electroretinogram measures in diabetic retinopathy

Both basic and clinical electrophysiological investigations have established that the oscillatory potentials (OP) and pattern electroretinogram (PERG) appear to originate from retinal sites that are in proximity. The OPs, subcomponents of the flash ERG, have been shown to reflect disturbances in retinal circulation, and OP amplitude attenuation or loss may be a distinctive feature of diabetic retinopathy. The PERG has been shown to be abnormal in diseases of the optic nerve and ganglion cell body. Thus its relative sensitivity for detection of electroretinal abnormalities in diabetic retinopathy is in question. This study assessed the sensitivity of ERG and OP measures in their detection of abnormalities of electroretinal function in diabetic patients referred to our laboratory. Thirty-five adult Type I patients were studied: 21 with background retinopathy (BR group), 14 with no evidence of background retinopathy (No BR group), and 25 normal control subjects.Monocular OPs were recorded to full-field ganzfeld stimulation at four stimulus intensities. PERGs were obtained from checkerboard pattern reversal stimulation (checksize = 30 arc). Peak-to-peak amplitude and peak implicit time measures of PERGs and OPs were obtained. Subsequent multivariate analysis demonstrated significant differences between normals and diabetic patients, including diabetics with no clinical evidence of retinopathy. In addition, the OP and PERG implicit times appear to be unaffected while OP and PERG amplitudes were diminished in patients with background retinopathy. Only OP amplitudes were found to be significantly diminished in diabetic patients with no photographic evidence of background retinopathy. The PERGs were normal in these patients. Overall, the OP amplitude measures were more sensitive than PERG measures in detecting abnormalities in patients with no retinal photographic evidence of background retinopathy.     

Microelectrode depth study of the electroretinographic oscillatory potentials in the frog retina

The depth profile of the electroretinographic oscillatory potentials was studied in the isolated frog retina. The intraretinal electrode was introduced from the receptor side, and the reference electrode was placed on the vitreal side. The electroretinogram, recorded either transretinally or with the electrode tip in the receptor layer, showed 4 to 10 oscillatory potential wavelets. As the electrode was advanced proximally, the wavelets disappeared as a function of retinal depth. The wavelets with longer peak latencies disappeared earlier, and only the first one or two wavelets could be identified when the electrode was in the inner plexiform layer. These findings indicate that the oscillatory potentials are generated between the inner and outer plexiform layers and that the earlier wavelets originate in the more proximal retina. The results are consistent with the notion that the oscillatory potentials are generated by synaptic feedback circuits.     

ERG electrode in pedriatic patients: Comparison of DTL fiber,PVA-gel,and non-corneal skin electrodes

Hard contact lens electrodes have been the type most frequently used in pediatric electroretinogroply but they are not well-tolerated by patients. The Dawson Trick Litzkow fiber electrode is better tolerated but it is fragile and difficult to sterilize. A new electrode made from anomalous polyvinyl alcohol gel is inexpensive, has stable electrical recording properties, and can be discarded after use. Dermal electrodes have been used for electroretinogram recording for some time; however, there are few reports that directly compare their performance against standard contact lens assemblies. We compared the DTL and the polyvinyl gel electrodes in the same group of subjects and investigated their recording characteristics along with non corneal skin electrodes placed on the infraorbital ridge. Signal-averaged electroretinogram were obtained under both scotopic and photopic stimulation conditions and the implicit time and amplitudes of the a- and b-waves were determined. Overall, dermal recordings generally had shorter implicit times and lower amplitudes than with the fiber or gel electrodes. The dermal electrodes were best tolerated and outlasted the corneal in repeated use. Since amplitude characteristics of the dermal electrodes were generally about 50% of that obtained with corneal electrodes, we feel that under standardized conditions they are acceptable for most clinical recording situations in infants and young children.     

The pattern electroretinogram by skin electrodes: Effect of spatial frequency and age

Steady-state (8 Hz) pattern electroretinograms in response to sinusoidal gratings were recorded from 18 elder subjects (mean age 62.7 years) and 22 young subjects (mean age 27 years) by means of skin electrodes. All subjects were free from ocular pathology and their corrected visual acuity was 1.0 or better. In young subjects the second harmonic amplitude as a function of spatial frequency is spatially tuned, with a maximum at around 1.7 c/deg. The response of elder subjects is significantly (P < 0.05) reduced over the whole range of spatial frequency as compared with that of younger ones. This decrease is more marked (P < 0.01) at intermediate spatial frequencies, resulting in a shallower tuning. The response phase is not significantly different between young and elder subjects.