172例多焦ERG检测分析

目的对172例患者行多焦视网膜电图检测。方法应用德国罗兰电生理仪检测,采用103个六边形刺激图形,记录172例患者多焦ERG的b波振幅密度值在六环的表现。结果多焦ERG表明各类眼底病变对视网膜损伤程度和范围是不相同的。结论多焦ERG检查具有局部定位和定量功能的诊断和分类,以及为眼底病变的早期诊断治疗提供依据具有重要意义。     

急性高眼压作用下视神经轴浆运输与视网膜光学功能的关系

目的:研究急性高眼压下视神经轴浆运输与视网膜光学功能之间的关系。方法:通过前房灌注的方法制造急性高眼压动物模型;利用罗兰电生理仪进行闪光视网膜电图和视觉诱发电位的测量。在玻璃体注射荧光染料后,利用激光共聚焦显微镜观察视神经轴浆运输,并利用苏木素-伊红染色,观察视乳头的形态变化。结果:当眼压为60 mm Hg并维持2 h,闪光视网膜电图的a波幅值明显降低,视网膜外层功能可能发生变化。当眼压为100 mm Hg并维持4 h,闪光视网膜电图的a波、b波和Ops的幅值以及闪光视觉诱发电位的幅值明显降低,视网膜内外层光学功能出现损伤,此时视神经的轴浆运输明显改变,视乳头形态也发生了变化。结论:急性高眼压下视神经轴浆运输与视网膜光学功能之间可能存在一定的关系。     

多焦视网膜电图多位点振幅概率图研究

多焦视网膜电图是用于检测视网膜后极部多个位点尤其是黄斑部功能的一种客观的眼电生理检查技术.本文记录并分析120位不同性别、不同年龄正常人的mfERG的103个刺激位点一阶反应振幅密度,按年龄、眼别统计出振幅密度正常值,自动画出异常概率图,并经过6例临床病人的mfERG数据验证,结果证实所得概率图与眼科医生的分析判断一致.     

不同MNU剂量诱导大鼠视网膜光感受器细胞损伤的视网膜电图和病理形态改变

目的： 探讨不同剂量N-甲基-N-亚硝脲（MNU）诱导的大鼠视网膜光感受器细胞损伤动物模型的眼电图和病理形态改变，寻找最适的MNU剂量。方法: 50 d龄雌性SD大鼠150只，随机分6组(每组25只大鼠)，即30 mg/kg、35 mg/kg、40 mg/kg、45 mg/kg和50 mg/kg MNU造模组和正常对照组，在造模后12 h、1 d、3 d、7 d和10 d测定大鼠的眼电生理，并取眼球进行病理检查。结果: 大鼠眼电生理结果显示，与正常组比较，30 mg/kg和35 mg/kg MNU组在各个时点对a波潜伏期和b波潜伏期的影响变化不大（P＞0.05）；a波振幅和b波振幅在第1、3 d下降较为明显(P＜0.05或 P＜0.01）。30 mg/kg和35 mg/kg MNU组在不同的时点:a波潜伏期、b波潜伏期、a波振幅和b波振幅明显高于40 mg/kg、45 mg/kg和50 mg/kg MNU组(P＜0.05或 P＜0.01）。45 mg/kg和50 mg/kg MNU组在不同的时点绝大多数呈现熄灭型电生理的表现。病理结果显示，在不同的时点，30 mg/kg和35 mg/kg MNU对大鼠视网膜光感受器细胞的损伤程度较轻，明显低于40 mg/kg、45 mg/kg和50 mg/kg MNU对大鼠视网膜外核层的损伤(P＜0.05或 P＜0.01）。损害程度为50 mg/kg＞45 mg/kg＞40 mg/kg。结论: 对大鼠视网膜光感受器细胞的病理和功能损害， 30 mg/kg和35 mg/kg MNU组损害较轻，40 mg/kg、45 mg/kg和50 mg/kg MNU组损害较重，40 mg/kg MNU是引起大鼠视网膜光感受器细胞最大损害的最低剂量。     

柔红霉素、骆驼蓬总碱对兔视网膜的毒性观察

目的 探讨药物柔红霉素(daunorubicin,DNR)、骆驼蓬总碱(total alkaloid Of Harmaline,TAH)眼内注射防治后发性白内障对视网膜的毒性作用.方法 于兔右眼晶体囊摘除(extracapsular lens extraction,ECLE)术中分别前房内注射0.2mg/mlTAH和0.2mg/ml DNR溶液0.1ml,通过眼底镜检查、视网膜电图及眼组织病理学等研究对象兔眼视网膜的影响.结果 对照眼与15只注入TAH眼眼底无明显的病理变化;TAH眼手术前后视网膜电图b波的振幅和潜时与对照眼无差别.而10只注入DNR眼出现严重的内皮性角膜水肿混浊,前房大量纤维索性渗出特等明显的炎性反应眼底及视网膜电图无法检查.组织病理学检查显示TAH组眼前节结构及视网膜各层结构正常,细胞排列规律;透射电镜检查TAH眼的视网膜感光细胞外节盘膜结构清晰.排列整齐.视网膜细胞排列紊乱,部分明显呈核固缩,表现出明显的毒性反应.结论 TAH眼内注射对兔视网膜的毒性较小,有可能用于后发性白内障的防治研究,而DNR对兔视网膜及其它组织表现出明显毒性,应进一步研究其使用的安全剂量和剂型.     

多焦技术及其在mERG中的应用

多焦技术是目前信号处理的一项先进技术,它在视觉电生理系统中的主要应用为多焦视网膜电图(multifocal electroretinogram,mERG)及多焦视诱发电位(multifocal visual evoked potential,mVEP)检测.其中,mERG可以同时刺激视网膜上多个小区域,在较短时间内反映各个小区域对应的ERG特性,从而精确快速敏感的测量视功能.本文主要从互相关函数、m-序列等入手介绍了多焦技术的原理,并对其在视网膜电图上的应用--多焦视网膜电图进行了描述,阐明了在多焦视网膜电图中如何对每个小区域的生理电响应信号进行分离.     

视网膜电图振荡电位的起源与特点

视网膜电图(ERG)振荡电位(Oscillatory Potentials,OPs)是叠加在b波上的频率较快的低小振荡电位,在大多数脊椎动物和人类均可以测得。1937年Granit和Münsterhjelm首先观察到青蛙ERG的b波上升支有一组振荡波,1953年Cobb和Morton报导了人ERG的b波上叠加的4～6个小波。随后,大量文献报告OPs反映了视网膜循环障碍,在某些疾病中OPs振幅选择性地降低。在糖尿病视网膜病变的研究中,OPs被认为是诊断和判断预后的重要手段。     

大鼠视网膜缺血再灌注损伤中视网膜电图的变化

目的：研究视网膜电图（ERG）在视网膜缺血再灌注损伤过程中的变化,探讨其临床应用价值。方法：24只一侧眼视网膜缺血SD大鼠随机分成损伤组、预处理组及丹参组每组8只。损伤组：大鼠视网膜在缺血60min后,分别经再灌注30min、24～72h后测量ERG。预处理组：大鼠视网膜在缺血后60min前24h行5min短暂缺血,再经上述再灌注时程后测量ERG。丹参组：大鼠缺血60min前30min球后注射复方丹参注射液0．05ml,再经上述再灌注时程后测量ERG。结果：损伤组各时程b波下降明显（P〈0．001）,预处理组及丹参组再灌注72h后b波恢复（P〉0．05）。结论：视网膜缺血再灌注损伤引起ERG的b波明显下降,ERG的b波是客观反映其损伤及功能恢复的敏感性指标。     

急性大鼠眼高压诱导的不同缺血/再灌内层视网膜的变化

目的：探讨急性眼高压诱导的不同缺血／再灌条件下内层视网膜形态与功能的变化。方法：成年大鼠,根据不同加压与再灌时间分组。左眼眼压升高至闪光视网膜电图b波消失的临界眼压且维持缺血30～90min。实验动物分别再灌1、3、7或14d复测b波,尼氏染色检测节细胞(RGCs)密度、内层视网膜厚度。结果：缺血60或90min组RGCs密度和内层视网膜厚度显著下降,且下降的程度随再灌时间的延长而加重。缺血30或45min组复测b波部分恢复;而缺血60min或更长时间组则b波未恢复。结论：缺血60min或更长时间导致内层视网膜严重损伤,而不同的眼高压维持时间和再灌时间都是影响视网膜损伤程度的重要因素。     

羊膜接触镜输送人表皮干细胞重建兔角膜上皮

目的 利用眼表生物膜固定装置(BMFD)与羊膜(AM)制成接触镜,输送人表皮干细胞至角膜缘干细胞缺损(LSCD)的兔眼表,并评价其重建角膜上皮的效果.方法 制作去角膜上皮及角膜缘干细胞的雌性LSCD兔模型,分为3组:羊膜加人表皮干细胞移植组(n=20),将男性人表皮干细胞悬液注射到BMFD-AM接触镜(简称羊膜接触镜)与眼表之间;羊膜遮盖组(n=20),戴羊膜接触镜;对照组(n=20),单纯药物治疗.裂隙灯显微镜结合角膜荧光素钠染色观察并评价角膜修复情况.随访至角膜完全上皮化后,取角膜组织行病理学检查和免疫组织化学鉴定,PCR检测人Y-STR基因鉴定细胞来源.结果 羊膜加人表皮干细胞移植组角膜上皮修复快,平均(5.60±0.46)d达到完全上皮化,另外两组角膜上皮修复迟缓.羊膜遮盖组(9.25±0.51)d、对照组(12.45±0.65)d才完成角膜上皮化(P均<0.05).组织病理学示羊膜加人表皮干细胞移植组角膜上皮细胞形态接近正常,K3/K12(+)、Mucin 5AC(-)、K4(-).并可检测到人Y-STR基因.组织病理学示另外两组角膜上皮结膜化,K4(+)、Mucin 5AC(+)、K3/K12(-).结论 羊膜接触镜联合人表皮干细胞悬液注射能够重建LSCD兔角膜上皮.     

Electroretinography in dogs using a fiber electrode prototype

We compared two electroretinography (ERG) electrodes in dogs using ERG standards of the International Society for Clinical Electrophysiology of Vision (ISCEV). Ten healthy Yorkshire terrier dogs (mean age, 2.80 ± 1.42 years; 6 females) weighing 5.20 ± 1.56 kg were evaluated using an ERG system for veterinary use. Dark- and light-adapted ERG responses were recorded using an ERG-Jet electrode and a fiber electrode prototype. The examinations were performed during 2 visits, 3 weeks apart. Both electrodes (ERG-Jet or fiber prototype) were used on each animal and the first eye to be recorded (OD × OS) was selected randomly. Three weeks later the examination was repeated on the same animal switching the type of electrode to be used that day and the first eye to be examined. The magnitude and waveform quality obtained with the two electrode types were similar for all ERG responses. ERG amplitudes and implicit times obtained from dogs using the fiber electrode prototype were comparable to those obtained with the ERG-Jet electrode for rod, maximal rod-cone summed, cone, and 30-Hz flicker responses. The fiber electrode prototype is a low-cost device, available as an alternative instrument for clinical veterinary ERG recording for retinal function assessment.     

A method of recording the local electroretinogram

Summary A method of recording the ERG from so-called local leads (placing the electrode on different parts of the cornea) was used. It was found that the amplitude of the ERG as recorded from different electrode positions was related to the site of the detachment. This effect cannot be obtained when the ERG is recorded by use of a contact lens.(Presented by Active Member AMN SSSR, A. V. Levedinskii) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 56, No. 7, pp. 120–123, July, 1963     

Elevated free calcium levels in the subretinal space elevate the absolute dark-adapted threshold in hypopigmented mice

Abundant evidence spanning 25 years demonstrates that hypopigmentation is associated with sensory abnormalities manifested most clearly as elevated absolute dark-adapted thresholds in hypopigmented mice. Here we show that when ocular melanin is increased in the himalayan mouse via alpha-melanocyte stimulating hormone (alpha-MSH) injections, dark-adapted thresholds drop in proportion to the change in ocular melanin. We further measured free calcium concentration with calcium-sensitive microelectrodes in both albino and black mouse retinal eyecups in living subjects. The recordings were done in anesthetized animals as the defect is not present in isolated retinas or in the superfused eye preparation. A double-barreled electrode--pCa and Vref--was used to simultaneously record the calcium concentration and the electroretinogram (ERG) at each of many depths as the electrode was driven through the retina. The position of the electrode was confirmed with ERG and 1,1'-dioctadecyl-3, 3,3',3'-tetramethylindocarbocyanine perchlorate electrode tract reconstruction. Dark-adapted albinos (n = 6) had 1.4 +/- 0.015 mM calcium in the subretinal space compared with 0.80 +/- 0.025 mM in black mice (n = 6). The results of these experiments are consistent with the hypothesis that ocular hypopigmentation causes elevated calcium levels in the subretinal space that in turn mimic light adaptation in hypopigmented mice.     

Forces developed beneath hydrogel contact lenses due to squeeze pressure

The hydrodynamic squeeze pressure in the fluid thin film beneath hydrogel contact lenses fitted onto an axisymmetric model eye were measured. These pressures were due to the contact lens relaxing after deformation by an applied force of similar magnitude to the human eyelid force. The distribution of pressure for contact lenses typically fitted to human eyes was negative with respect to atmospheric pressure at the corneal apex and became less negative at the corneo-scleral limbus. The force that the contact lens applied to the cornea was determined by integrating the pressure distribution from the corneal apex to the limbus. This force varied from 6.0 X 10(-4) N to -7.8 X 10(-1) N depending on the thickness, elastic modulus and bearing relationship of the contact lens. An expression was derived to determine the pressure developed beneath the annulus of the hydrogel contact lens overlapping the cornea, in terms of the measured force over the cornea beneath the contact lens and the chord diameters of the contact lens and cornea. It was found that the deformation of hydrogel contact lenses on the model eye did not follow a linear elastic shell theory.     

Effect of thermal preconditioning before excimer laser photoablation

The purposes of this study were to assess the expression patterns of heat shock proteins (Hsps), after eyeball heating or cooling, and to elucidate their relationships with corneal wound healing and intraocular complications after excimer laser treatment. Experimental mice were grouped into three according to local pretreatment type: heating, cooling, and control groups. The preconditioning was to apply saline eyedrops onto the cornea prior to photoablation. Following photoablation, we evaluated corneal wound healing, corneal opacity and lens opacity. Hsp expression patterns were elucidated with Western blot and immunohistochemical staining. The heating and cooling groups recovered more rapidly, and showed less corneal and lens opacity than the control group. In the heating and cooling groups, there were more expressions of Hsps in the cornea and lens than in the control group. These results were confirmed in the Hsp 70.1 knockout mouse model. Our study showed that Hsps were induced by the heating or cooling preconditioning, and appeared to be a major factor in protecting the cornea against serious thermal damage. Induced Hsps also seemed to play an important role in rapid wound healing, and decreased corneal and lens opacity after excimer laser ablation.     

Electroretinographic wet electrode

This paper presents the first systematic characterisation of a new electroretinographic (ERG) electrode, recently described. The new ‘wet’ electrode uses a conducting liquid as a distributed electrical interface between the eye and a solid electronic conductor; the latter detects the ERG potential without any direct contact with the ocular surface. This technique avoids the contact-induced discomfort of both corneal and conjunctival standard electrodes. The wet electrode was tested on 10 volunteers, in comparison with a conjunctival electrode (HK loop), as the most comfortable standard. It was also compared with a cutaneous (cup) electrode, which is even more comfortable, although not standard. Results showed the efficacy of the wet electrode for detecting morphologically accurate ERG responses, with amplitudes respectively analogous and higher of those measured by the conjunctival and cutaneous electrodes. Properties of wet electrodes include: no solid interface with the eye, no need for anaesthesia, intrinsic safety, mechanical and electrical stability against ocular movements, tolerance to misplacements and immunity to lacrimation. As a drawback, the liquid can still be a source of discomfort for some patients and it requires care against possible leakage. All these features suggest a possible use of wet electrodes as an additional tool for ERG procedures, although limited to tests of short duration.     

Contribution of voltage-gated sodium channels to the b-wave of the mammalian flash electroretinogram

Voltage-gated sodium channels (Na(v) channels) in retinal neurons are known to contribute to the mammalian flash electroretinogram (ERG) via activity of third-order retinal neurons, i.e. amacrine and ganglion cells. This study investigated the effects of tetrodotoxin (TTX) blockade of Na(v) channels on the b-wave, an ERG wave that originates mainly from activity of second-order retinal neurons. ERGs were recorded from anaesthetized Brown Norway rats in response to brief full-field flashes presented over a range of stimulus energies, under dark-adapted conditions and in the presence of steady mesopic and photopic backgrounds. Recordings were made before and after intravitreal injection of TTX (approximately 3 microm) alone, 3-6 weeks after optic nerve transection (ONTx) to induce ganglion cell degeneration, or in combination with an ionotropic glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 200 microm) to block light-evoked activity of inner retinal, horizontal and OFF bipolar cells, or with the glutamate agonist N-methyl-D-aspartate (NMDA, 100-200 microm) to reduce light-evoked inner retinal activity. TTX reduced ERG amplitudes measured at fixed times corresponding to b-wave time to peak. Effects of TTX were seen under all background conditions, but were greatest for mesopic backgrounds. In dark-adapted retina, b-wave amplitudes were reduced only when very low stimulus energies affecting the inner retina, or very high stimulus energies were used. Loss of ganglion cells following ONTx did not affect b-wave amplitudes, and injection of TTX in eyes with ONTx reduced b-wave amplitudes by the same amount for each background condition as occurred when ganglion cells were intact, thereby eliminating a ganglion cell role in the TTX effects. Isolation of cone-driven responses by presenting test flashes after cessation of a rod-saturating conditioning flash indicated that the TTX effects were primarily on cone circuits contributing to the mixed rod-cone ERG. NMDA significantly reduced only the additional effects of TTX on the mixed rod-cone ERG observed under mesopic conditions, implicating inner retinal involvement in those effects. After pharmacological blockade with CNQX, TTX still reduced b-wave amplitudes in cone-isolated ERGs indicating Na(v) channels in ON cone bipolar cells themselves augment b-wave amplitude and sensitivity. This augmentation was largest under dark-adapted conditions, and decreased with increasing background illumination, indicating effects of background illumination on Na(v) channel function. These findings indicate that activation of Na(v) channels in ON cone bipolar cells affects the b-wave of the rat ERG and must be considered when analysing results of ERG studies of retinal function.     

Effects of dystrophin isoforms on signal transduction through neural retina: genotype-phenotype analysis of duchenne muscular dystrophy mouse mutants

Duchenne and Becker muscular dystrophy patients have mutations in the dystrophin gene. Most show reduced b-wave amplitudes in the dark-adapted electroretinogram (ERG). We studied normal C57BL/6J mice and five X-linked muscular dystrophy strains with different dystrophin mutations to determine whether the location of the mutation within the gene affects the mouse ERG and to correlate such effects with dystrophin isoform expression. Amplitudes and implicit times were measured for a-waves, b-waves, and digitally filtered oscillatory potentials. mdx and mdxCv5 mice, with mutations near the amino terminus and lacking expression of Dp427, had ERGs similar to those of C57BL/6J mice. mdxCv2 and mdxCv4 mice, with mutations in the center of dystrophin and who do not express isoforms Dp427, Dp260, or Dp140 (mdxCv4), had increased b-wave and oscillatory potential implicit times. mdxCv3 mice, with a mutation near the carboxy terminus resulting in deficiency of all dystrophin isoforms, had increased b-wave and oscillatory potential implicit times and reduced scotopic b-wave amplitudes. Fitting the a-wave data to a transduction activation phase mathematical model showed normal responses for all phenotypes, suggesting that the b-wave delays are due to defects beyond the rod outer segment, most likely at the rod to on-bipolar cell synapse. The variation in the ERG phenotype with the position of the dystrophin gene mutation suggests that there are different contributions by each isoform to retinal electrophysiology. Although Dp427 and Dp140 isoforms do not appear to be important contributors to the ERG, lack of Dp260 and possibly Dp71 isoforms is associated with an abnormal ERG.     

Disruption of anterior segment development by TGF-beta1 overexpression in the eyes of transgenic mice.

Previous experiments showed that transgenic mice expressing a secreted self-activating transforming growth factor (TGF) -beta1 did not show a phenotype in the lens and cornea until postnatal day 21, when anterior subcapsular cataracts, sporadic thickening of the corneal stroma, and thinning of the corneal epithelium were noted (Srinivasan et al., 1998). To examine the effects of higher concentrations of TGF-beta1 on the lens and cornea, we constructed transgenic mice harboring the strong, lens-specific chicken betaB1-crystallin promoter driving an activated porcine TGF-beta1 gene. In contrast to the earlier study, the transgenic mice had microphthalmic eyes with closed eyelids. Already at embryonic day (E) 13.5, the future cornea of the transgenic mice was threefold thicker than that of wild-type littermates due to increased proliferation of corneal stromal mesenchyme cells. Staining of fibronectin and thrombospondin-1 was increased in periocular mesenchyme. At E17.5, the thickened transgenic corneal stroma was vascularized and densely populated by abundant star-shaped, neural cell adhesion molecule-positive cells of mesenchymal appearance surrounded by irregular swirls of collagen and extracellular matrix. The corneal endothelium, anterior chamber, and stroma of iris/ciliary body did not develop, and the transgenic cornea was opaque. Fibronectin, perlecan, and thrombospondin-1 were elevated, whereas type VI collagen decreased in the transgenic corneal stroma. Stromal mesenchyme cells expressed alpha-smooth muscle actin as did lens epithelial cells and cells of the retinal pigmented epithelium. By E17.5, lens fiber cells underwent apoptotic cell death that was followed by apoptosis of the entire anterior lens epithelium between E18.5 and birth. Posteriorly, the vitreous humor was essentially absent; however, the retina appeared relatively normal. Thus, excess TGF-beta1, a mitogen for embryonic corneal mesenchyme, severely disrupts corneal and lens differentiation. Our findings profoundly contrast with the mild eye phenotype observed with presumably lower levels of ectopic TGF-beta and illustrate the complexity of TGF-beta utilization and the importance of dose when assessing the effects of this growth factor.     

Electroretinograms Reveal No Evidence for Centrifugal Modulation of Retinal Inputs During Selective Attention in Man

Eason, Oakley, and Flowers (1983, Physiological Psychology, 11, 18–28) have recently described changes in the B-wave and after-potential of the human electroretinogram (ERG) during spatial selective attention. These results suggested that centrifugal modulation of retinal input may play a role in visual attention. We investigated this effect in two experiments in which subjects attended to sequences of flashes in one visual half-field while ignoring similar flashes in the opposite half-field. Visual event-related potentials (ERPs) were recorded from electrodes placed at periorbital and scalp sites, while the ERG was simultaneously recorded using a gold-foil electrode contacting the cornealscleral surface of the right eye. Selective visual attention was evident in an enhancement of the scalp-recorded N150 component of the visual ERP to flashes in the attended half-field. However, no effect of attention was observed on the B-wave or after-potential of the ERG. Long-latency positive shifts related to attention were demonstrated in the corneal-scleral recording and are discussed with respect to volume-conducted brain activity.