Electroretinographic Changes Research Articles

Clinical and Histologic Effects of Extreme Intraocular Hypothermia

Rabbit eyes in which vitrectomy was performed underwent three hours of hypothermic perfusion with either 22 C or 2 C lactated Ringer's solution. Clinical, electroretinographic, fluorescein angiographic, histologic, and ultrastructural examinations were performed. No changes were noted in eyes cooled with 22 C fluid. Reversible lens opacities, equivocal electroretinographic changes, and subclinical retinal detachments were found in the eyes cooled with 2 C fluid. Extreme cooling of eyes is not advisable, although temperatures of 22 C are well tolerated.

Electroretinographic changes induced by organophosphorus pesticides in rats.

Electroretinographic changes induced by organophosphorus pesticides (OPs) were studied in rats. Male Wistar rats were intraperitoneally injected with fenthion, chlorpyrifos, fenitrothion, dichlorvos or chlorfenvinphos at doses of 0.01 mmol/kg and/or 0.05 mmol/kg. The electroretinogram (ERG) was recorded at 5 hours and 2 days after the administration, and brain and retinochoroid cholinesterase (ChE) activities was assayed at 3 days after the injections. The brain and retinochoroid ChE activities were reduced in rats treated with the OPs. Notably, the reduction of ChE activities by fenthion, chlorpyrifos and dichlorvos were similar. The administration of OPs induced a change in the ERG, characterized by alteration of the amplitudes of a- and b-waves. Nevertheless the ChE activities in the brain and retinochoroid were inhibited by all of the OPs, the OPs affected the amplitude of ERG differently. Fenthion and chlorpyrifos decreased the amplitudes; dichlorvos and chlorfenvinphos increased; and fenitrothion transiently decreased at 5 hours but increased 2 days after the injection. These results indicate that a factor or factors other than inhibition of ChE activities contributes to the alteration of ERG induced by OPs.

Intracameral Thrombin and the Corneal Endothelium

We perfused the endothelia of isolated human corneas mounted in the specular microscope with BSS Plus containing 1,000-U/ml or 100-U/ml dilutions of two commercially available topical thrombin preparations. Corneas perfused with thrombin at 1,000 U/ml showed intracellular and intercellular vacuole formation and altered junctional complexes. As listed on the package inserts, the thrombin preparations contained preservatives and other additives that present a significant osmotic load in 1,000-U/ml preparations. Corneas perfused with 100-U/ml thrombin solutions showed a significant attenuation in their deswelling rate but no ultrastructural alterations. One available thrombin preparation when diluted to 100 U/ml had a glycine concentration associated with previous retinal electroretinography changes. Polyacrylamide gel electrophoresis of one manufacturer's thrombin solution showed multiple high and low molecular weight constituents. Analysis of particulate contamination showed one 100-U/ml thrombin preparation to have a large quantity of particulates. Although thrombin may be useful when applied topically as an aid in surgical hemostasis, its use intraocularly presents substantial concern regarding the preparation's purity, additives, contaminants, and adverse effects on ocular tissues.

Experimental posterior uveitis. II. Electroretinographic studies.

Experimental posterior uveitis was induced by the inoculation of retinal S-antigen into black hooded Lister rats. The time course of the disease was monitored by electroretinography (ERG), and the ERG changes were correlated with clinical signs and underlying pathological damage. The ERG became supernormal in the third week after inoculation, with some loss of temporal resolution (lowered ERG flicker fusion frequency), though the disease was not clinically manifest at this time and histological examination was normal. The ERG became subnormal after 21 days as clinical signs of disease began to appear. This subnormality was associated with focal photoreceptor necrosis, the degree of destruction being proportional to the reduction in the ERG. The ERG recovered with resolution of disease in most cases, though return to control values was uncommon. We suggest that the initial supernormal ERG reflects an underlying biochemical change mediated by the action of anti retinal S-antigen antibodies.

Liposome-bound cyclosporine: retinal toxicity after intravitreal injection.

The retinal toxicity of intraocular liposome-bound cyclosporine was studied in albino rabbits by means of electrophysiology and histopathology. During a followup period of one month, no histopathological or electroretinographic changes were noted using concentrations of 100, 200 and 500 micrograms injected intravitreally.

Surface area sized of intravitreal iron wires: their effects on the electroretinograms of rats.

The electroretinogram (ERG) was recorded 20 times over a period of 360 days in 26 albino-rats with implanted intravitreal iron wires ranging in size between 0.15 and 1.2 mm2. (i) The a- and b-wave amplitudes decreased rapidly within one day after iron wire implantation. During the following week the amplitudes recovered to some extent. In the course of the next few months the a- and b-wave amplitudes of the eyes implanted with the largest iron wires (1.2 mm2) decreased steadily to about 20% by the end of the observation time, whereas in the groups containing smaller iron wires the electroretinographic changes were limited. (ii) Implantation of equally-sized glass splinters reduced the a- and b-wave amplitudes to 65-75% in comparison to the intact fellow eye. Fast recovery of both potentials to 83-93% followed within two weeks. The mean values of the a-wave amplitudes reached nearly 100%, those of the b-wave 90-95% in the next month.

Gyrate Atrophy of the Choroid and Retina: The Ocular Disease Progresses in Juvenile Patients despite Normal or Near Normal Plasma Ornithine Concentration

Hyperornithinemia disappeared in three children with Gyrate atrophy of the choroid and retina during a low-arginine diet for 3 to 4 1/2 years. Because of the young age of the patients, we had an exceptional opportunity to follow the progression of the disease during this period. Despite the excellent biochemical control, electroretinographic changes progressed in two patients, and the chorioretinal atrophy progressed steadily in all the patients throughout the diet. Dark adaptation and color vision remained stable. In these patients, the normo-ornithinemia has not been able to halt the progression of the chorioretinal degeneration.

RETINAL TOXICITY OF GANCICLOVIR IN VITRECTOMY INFUSION SOLUTION

The authors investigated the retinal toxicity of the antiviral agent ganciclovir after its addition to vitrectomy infusion fluid in rabbit eyes. Intravitreal infusion of the drug in concentrations up to 30 micrograms/ml produced no electroretinographic or histologic changes suggestive of retinal toxicity. Ganciclovir in vitrectomy infusion fluid has potential therapeutic benefit in viral retinitis (particularly in cytomegalovirus retinitis) associated with vitreous traction or rhegmatogenous retinal detachment. Based on the median inhibitory doses of ganciclovir against various herpes group viruses and the results of this study, a concentration of 30 micrograms/ml or less of the drug is recommended for vitrectomy infusion solution.

Retinal Toxicity Study of Intravitreal Cyclosporin

We investigated the toxicity of intravitreal cyclosporin in the rabbit. Histologic retinal changes were found with intravitreal injections of 200 micrograms. No histologic or electroretinographic changes were observed with doses of 100 micrograms or less. This nontoxic dose is projected to be at least 77 times the amount needed to be effective.

Effect of adriamycin on experimental proliferative vitreoretinopathy in the rabbit

The cell injection model of proliferative vitreoretinopathy (PVR) in the rabbit was used to study the therapeutic value of intravitreal adriamycin (doxorubicin). Adriamycin in a dose of 10 nmol per eye, if injected at the same time as the cells, controls PVR. At the cell doses used, PVR is not affected if there is a time interval between cell and drug injection. Because of retinal toxicity, as evidenced by electroretinographic and histopathologic changes, the beneficial effects of adriamycin on membrane formation cannot be exploited at this time.

Retinal pigment epithelial dysfunction in early ovine ceroid lipofuscinosis: electrophysiologic and pathologic correlates.

Retinal degeneration is a major finding in the human and ovine ceroid lipofuscinosis. Sequential electroretinographic (ERG) studies in a young, asymptomatic, affected lamb are presented here, which demonstrate a progressive loss of the scotopic b-wave and unrecordable c-waves under halothane anesthesia. Even at this initial stage of disease, lesions were evident in the form of dystrophic retinal pigment epithelial (RPE) villi, and loss of photoreceptor cells and rod outer segments. Cone inner segments were enlarged and scanning electron microscopy emphasized these abnormalities. All cells in tapetal and nontapetal areas contained fluorescent inclusions with similar emission spectra (maximum = 539 nm). By transmission electron microscopy, storage bodies consisted of 'finger-print' profiles and were most prominent in bipolar cells. The pathological features of the retina correlate well with the observed ERG changes, reaffirming the sheep as a useful model to delineate early events in ceroid lipofuscinosis.

Moxalactam retinal toxicity.

Moxalactam disodium is a new third-generation semisynthetic, broad-spectrum, cephalosporin-like antibiotic for parenteral administration. Topical, subconjunctival, and intravenous administration provide poor concentration in the vitreous. To determine its toxicity in intravitreal administration, we injected comparative doses directly into the vitreous cavity of 21 rabbits. With doses of 1.25 mg or less there was no toxic damage to the retina. With a dose of 2.5 mg, early degeneration of photoreceptors was seen after three months. With higher doses (5 and 10 mg) there were major histopathologic and electroretinographic changes. These results suggest the feasibility of employing moxalactam in the treatment of acute, severe, fulminant bacterial endophthalmitis.

Effect of gamma-aminobutyric acid agonists, glycine, taurine and neuropeptides on acetylcholine release from the rabbit retina.

The light-evoked release of [3H]acetylcholine (ACh) from the rabbit retina in vivo was measured and taken as an index of cholinergic amacrine cell activity. The light-evoked release of [3H]ACh was reduced by locally applied gamma-aminobutyric acid (GABA), muscimol and 3-aminopropanesulphonic acid (3-APS). The concentrations of these drugs which reduced the light-evoked release of [3H]ACh by 50% (EC50) were 900, 0.3 and 5 microM respectively. In contrast, (-)-baclofen (5 mM), but not (+)-baclofen, significantly increased the light-evoked release of [3H]ACh. The GABA antagonist, bicuculline increased the resting release of [3H]ACh but abolished the inhibitory action of muscimol on the light-evoked release of [3H]ACh. Glycine and taurine also reduced the light-evoked release of [3H]ACh from the retina, their EC50 values being 1.5 and 0.3 mM respectively. This action was blocked by strychnine, but not by bicuculline. In contrast to the GABA antagonist, strychnine did not affect the spontaneous resting release of [3H]ACh. Retinal [3H]ACh release was not affected by dopamine, 5-hydroxytryptamine (5-HT) morphine, substance P, somatostatin, cholecystokinin sulphate, thyrotropin releasing hormone, luteinizing hormone releasing hormone or angiotensin. Electroretinographic changes produced by amino acids and GABA agonists involved mainly the b-wave and were not correlated with their effects on ACh release. Thus, GABA increased the b-wave amplitude, 3-APS had no effect, whilst muscimol, taurine and glycine either had no effect, or reduced the b-wave amplitude. No obvious changes in the e.r.g. were produced by baclofen, dopamine, 5-HT, morphine or any of the peptides studied with the exception of somatostatin, which reduced the amplitude of the b-wave. It is concluded that cholinergic amacrine cell activity in the rabbit retina may be affected by inputs from other amacrines using GABA or glycine (taurine) as their transmitters, but probably not by inputs from peptidergic or dopaminergic amacrine cells. Our experiments do not provide evidence on the sites of action of GABA, glycine or taurine but the action of bicuculline on the resting release of ACh implies that the activity of the cholinergic amacrine cells is affected by a tonically active GABAergic input.

Toxicity of intravitreous miconazole.

Miconazole nitrate is a broad-spectrum antimycotic agent with low systemic and ocular toxicity. Since this drug does not adequately penetrate the vitreous cavity by topical, subconjunctival, or intravenous routes, we determined whether it can be given intravitreously for fungal endophthalmitis. Retinal and lens toxicity studies were carried out in 40 rabbits and three owl monkeys. Results showed that both miconazole and its vehicle produced toxic damage to the retina and crystalline lens in concentrations of 100 micrograms or greater. Concentrations of 10 to 80 micrograms caused mild to moderate retinal necrosis in some rabbit eyes. In monkey eyes, these concentrations did not cause significant histopathologic or electroretinographic changes. We believe that clinical use of this drug in doses not to exceed 40 micrograms may be justified in desperate cases of fungal endophthalmitis.

Visual Electrodiagnosis in Systemic Diseases: Proceedings of the 17th International Society of Clinical Electrophsiology of Vision Symposium

The 17th meeting of the International Society of Clinical Electrophysiology of Vision (ISCEV) was conducted near Erfurt, East Germany, in 1979. The main topics were Visual Electrodiagnosis in Systemic Diseases, and Visual Electrophysiology and Localized Stimulation. Forty-three contributions are contained in this book. Schmoger, who organized the ISCEV for the second time, introduced the main topic comprehensively including useful tables and supportive bibliography. Francois and De Rouck drew attention to the possible usefulness of the electro-oculogram (EOG) under acetazolamide administration for localization of degeneration in Bruch's membrane. Patients with scleroderma and Ehlers-Danlos syndrome show reduced b-wave amplitudes under this condition. Findings from an electroretinogram and EOG do not contribute to the diagnosis of carotic artery occlusion. The experimentally produced streptozotocin-diabetes, when treated with multiple daily doses of insulin, showed a decreased incidence of electroretinographic changes when compared with single-dose treatment. Betamethasone and dexamethasone (steroid) treatment of rabbits does not

Diffuse Unilateral Subacute Neuroretinitis

Thirty-six young healthy patients developed a peculiar clinical syndrome affecting only one eye. The early stage of the disease was characterized by visual loss, vitritis, mild papilledema, and successive crops of multiple, evanescent, gray-white, deep, retinal lesions. Over a period of many months there developed widespread, diffuse and focal depigmentation of the pigment epithelium, retinal arterial narrowing, optic atrophy, severe visual loss, and electroretinographic changes. A motile, subretinal round worm, probably a Toxocara, was observed in two patients.

Electroretinography and Diagnosis of the Laurence-Moon-Bardet-Biedl Syndrome in Childhood

The cases of two children affected from LMBB syndrome are reported. The first child was six years old, suffering from obesity and mild mental retardation; the other was two years old, suffering from hexadactyly and obesity. In both children the suspected diagnosis of LMBB syndrome was verified by the electroetinographic evidence of a tapetoretinal degeneration although the fundi were atypical. A third child, the younger brother of the second case, presented an atypical pigmentation of the retina and the electroretinographic changes of a tapeto-retinal degeneration. Since tapeto-retinal degeneration, which is the most common of the main signs of the syndrome, is not always recognized by ophthalmoscopy in early childhood, the clinical value of electroretinography in making an early diagnosis is emphasized.

Experimental siderosis in the rabbit: correlation between electroretinography and histopathology.

An iron foreign body was placed into the vitreous cavity of 22 rabbits' eyes. The electroretinographic (ERG) changes over a-15-week period were recorded. These changes were compared to those in a group of 12 normal rabbits and a group of 5 animals in whom a sham operation was performed. Twelve eyes were enucleated during this period and examined histopathologically. Histopathologic and functional changes in siderosis were both progressive in time, but the ERG values were more consistent among the 22 animals than the morphologic changes. Iron oxidation (Fe0 leads to Fe2 leads to Fe3) was found and suggested to be the mediating factor of the direct iron cytotoxic effect on the retina.

Electroretinographic Changes and Choroidal Defects in a Case of Central Retinal Artery Occlusion

A 62-year-old white woman with hypertensive diabetes had central retinal artery occlusion of her right eye. Serial electroretinographic (ERG) studies demonstrated reversible changes in the scotopic components but permanent reduction of the photopic b-wave. Serial simultaneous fluorescein and indocyanine green angiographic studies demonstrated a perfusion defect in the choroid involving part of the macula which subsided after reopening the retinal circulation. Differential hypoxic susceptibility of the ERG photopic and scotopic b-waves was demonstrated, and changes in the patient's retinal tissue oxygenation were postulated on the basis of retinal and choroidal angiographic studies performed during and after central retinal artery occlusion to account for the observed changes in serial ERGS.

Correlation of Histologic and Electroretinographic Changes in Peripheral Retinal Ablation in the Rhesus Monkey

We studied the effect of peripheral retinal ablation on the electroretinograms of five rhesus monkeys. An ablation procedure analogous to that commonly used in the treatment of diabetic retinopathy was carried out with an argon laser photocoagulator. Quantitative histologic measures showed retinal destruction of about 13% of total retinal area. This was associated with about a 50% reduction in scotopic electroretinographic amplitude.