ERG findings in three hypothyroid adult dogs with and without levothyroxine treatment.

PURPOSE: To evaluate the effects of levothyroxine (LTh) on the electroretinogram (ERG) of adult dogs. MATERIAL AND METHODS: Binocular, full field photopic and scotopic ERGs were recorded from an anesthetized Maltese Bichon cross (MB), a Yorkshire Terrier (YT) and a Shetland Sheepdog (SS) affected with hypothyroidism and treated with a daily dose of LTh at 20 microg/kg. The photopic ERGs were evoked to 12 different intensities ranging from 0.81 to -2.19 log cd.s/m(2) and presented under photopic conditions in order to assess (from the derived luminance-response curves) Vmax and b : a amplitude ratio parameters. Photopic flicker ERGs were obtained at 30 Hz. The scotopic ERGs (intensity: -3.09 log cd.s/m(2)) were recorded while the retina was dark-adapting and after 32 min of dark adaptation. This procedure was performed on two separate sessions: following a 3-day interruption of LTh treatment (S1) and following 30 days without interruption of LTh treatment (S2). RESULTS: The mean photopic a-wave peak times were 9.8 ms at S1 and 5.0 ms at S2, respectively. The mean photopic b-wave peak times were 23.3 ms at S1 and 11.5 ms at S2, respectively, and the mean scotopic b-wave peak times (after 32 min of dark adaptation) were 45.2 ms at S1 and 26.0 ms at S2, respectively. No other significant ERG changes were observed. CONCLUSION: Our results indicate that a dose of 20 microg/kg of LTh given to adult dogs was accompanied by a marked peak time shortening of both photopic and scotopic ERGs, without affecting other ERG parameters.

[Neurophysiological basis and clinical tests for assessment of X-linked color vision deficiencies in school children]. / Comprendre et tester les déficiences de la vision des couleurs de l'enfant, en pratique.

Vision screening of school children at 5-6 years of age must include color vision screening. X-linked dyschromatopsia is the most frequent disorder affecting 8% of boys and 0.4% of girls. This paper presents the physiology of these deficiencies caused by an alteration of the spectral absorption properties of one of the cone pigments (protanomalous or deuteranomalous trichromats) or the absence of one of the pigments (protanopia or deuteranopia), the most frequent. Absence of two of the pigments (blue cone monochromacy) is very rare and differs from achromatopsia. The physiological basis of the main tests for easy clinical screening are presented. Testing methods designed for children are reviewed. The Ishihara test is the most widely used screening test specific for congenital color defects. If the plates are correctly read, the child has normal color vision. If not, arrangement tests such as Panel D 15 and desaturated Panel D 15 tests can be used to diagnose the type of the defect (protan or deutan) and grade the degree of color deficiency according to a strategy adapted to children. Examples of results are presented for each axis along which caps are confused, providing a quick and easy preliminary diagnosis. Early detection of color vision malfunction in children allows parents and teachers to make necessary adjustments to the teaching methods for appropriate learning.

[Up-dated ophthalmological screening and follow-up management for long-term antimalarial treatment]. / Surveillance ophtalmologique de la prise des antipaludéens de synthèse au long cours: mise au point et conduite à tenir à partir de 2003.

The early detection of macular toxicity linked to long-term antimalarial treatment requires regular ophthalmological screening based on patients'classification based on their results compared to successive controls. Patients are classified as "low risk" with screening every 18 months if all of the following criteria are met: age under 65 years, no associated renal, hepatic or retinal disease, treatment for less than 5 years, dose less than or equal to 6,5mg/kg/d for hydroxychloroquine and 3mg/kg/d for chloroquine (for a lean patient's weight); "at risk, without fundus findings" with screening every 12 months if one of the following criteria is met: age over 65 years (at the start of or during treatment), antimalarial treatment for more than 5 years, daily dose higher than recommended, presence of renal and/or hepatic disease; "at risk, with fundus findings" with screening every 6 months if a retinal dysfunction has been detected and even if treatment is established or followed. Screening consists of an in-depth clinical examination and at least two complementary tests of macular function: color vision (desaturated-Panel-D15 test) and/or static macular perimetry (central 10 degrees) and/or macular electroretinography (pattern ERG/multifocal ERG). If any changes or anomalies are found between two successive check-ups, the state of the retina can be assessed by angiography and global retinal function by full-field-ERG and electro-oculogram (EOG). The progression from one check-up to the next decides whether a course of treatment will be followed.

[A new model of induced ocular hyperpressure using the minipig]. / Un nouveau modèle d'hyperpression oculaire induite chez le miniporc.

PURPOSE: To characterize a new animal model of moderate chronic hyperpressure obtained by obstruction of the iridocorneal angle (ICA) in the minipig. METHODS: Intraocular hyperpressure was induced in one eye (left) using an injection of methylcellulose (4%) in the anterior chamber of six healthy adult minipigs. Intraocular pressure (IOP) was measured before injection and at D+60 and D+180. The clinical condition thus created was regularly assessed with the following procedures: fundus photography, electroretinography (ERG) to evaluate retinal function, scanning laser ophthalmoscopy (SLO) angiography to measure the arteriovenous filling times (AVFT). Optical microscopy was also performed to evaluate iridocorneal angle and inner retinal layers. RESULTS: In all instances the injection produced a significant increase in the IOP accompanied by a mydriasis, as well as a significant increase in the AVFT and reduction (abolition in some cases) in the i-wave of the ERG. Fundus examination also revealed a blurred aspect and reduction in the calibre of the retinal blood vessels. Similarly, all experimental eyes showed, at optical microscopy, obstruction of the ICA as well a significant loss of of retinal ganglion cells. CONCLUSION: Our results suggest that the above pathophysiological processes, triggered by the induced hyperpressure, share many similarities with human chronic open-angle glaucoma. Consequently, our model, which is very easy to create, could be used to test new therapeutic agents such as neuroprotective drugs.

[Anatomy, physiology, and functional exploration of the optic nerve]. / Anatomie, physiologie et explorations fonctionnelles du nerf optique.

Disturbances of the optic nerve make up a large part of neuro-ophthalmology. They consist in large part of glaucoma and toxic inflammation of the optic nerve (retro-bulbar optic neuropathy). Progress in the understanding of the function of ganglion cells, in particular the discovery of the M and P pathways, comprise a considerable advance in the comprehension of the optic system as a whole. Progress in techniques of studying the visual field, the ERG pattern and imaging of the pupil have an influence on the diagnosis, the follow-up and the initiation of new therapeutic strategies in glaucoma and disorders of the SEP.

[Functional visual explorations of Bardet-Biedl syndrome. A study of three cases]. / Exploration fonctionnelle visuelle dans le syndrome de Bardet-Biedl. A propos de 3 cas.

Laurence-Moon syndrome, which is very rare, and Bardet-Biedl syndrome, which is more frequent are now well-recognized as two distinct entities in pediatric neurology. Bardet-Biedl syndrome includes a number of common clinical signs it shares with Laurence-Moon syndrome but also with other syndromes, particularly Alströme syndrome. These signs are retinitis pigmentosa, mental retardation, obesity, and hypogonadism. Ophthalmological and electrophysiological examinations are essential for confirmation and correct diagnosis of Bardet-Biedl syndrome. We present three case histories. Our third case illustrates the possibility of below normal yet discernable electroretinogram amplitudes which do not infirm the diagnosis of Bardet-Biedl syndrome.

Recording the photopic electroretinogram from conscious adult Yucatan micropigs.

The micropig is viewed by many as one of the best animal models of human system physiology. The purpose of this study was to develop a simple, rapid and reliable method to record clinical electroretinograms from conscious adult Yucatan micropigs. Photopic ERGs were recorded from 18 conscious animals following a 3-h period of preadaptation to a moderate photopic environment. Rectal temperature and blood pressure were monitored throughout the experiment. In order to test the reproducibility of our procedure, the same protocol was repeated (n=6 micropigs) on three different recording sessions each separated by a 48-h period. Our results indicate that the recording of reproducible ERGs, in the conscious Yucatan micropig, is feasible provided that an adequate experimental approach is used. We believe that our method will enable investigators to perform retinal physiology experiments using an approach which is compatible with that used in a human clinical setup thus facilitating the transposition of experimental data from animal to human.

Functional assessment of macular hole surgery by scanning laser ophthalmoscopy.

OBJECTIVE: This study aimed to evaluate more precisely the benefit of macular hole surgery. DESIGN: The design was a prospective study of 40 eyes in 40 patients examined before and after surgery of full-thickness macular holes with a scanning laser ophthalmoscope (SLO). PARTICIPANTS: Forty patients with full-thickness macular holes participated. Three of the holes were stage 2, 23 were stage 3, and 14 were stage 4. INTERVENTION: The SLO examination consisted of macular imaging and assessment of macular function using tests produced by an acousto-optical modulator. MAIN OUTCOME MEASURES: Preferred retinal locus (PRL) was determined, visual acuity was measured, and scotoma was detected by microscotometry and by the line test (modified Watzke-Allen test). RESULTS: Anatomic success was achieved in 32 of 40 cases as assessed biomicroscopically. On SLO examination before surgery, macular holes were seen as a central bright round disc outlined by a thin dark edge surrounded by a dark ring and a less dark area with ill-defined limits. In all cases, the PRL was located on the upper edge of the hole, a scotoma was always detected inside the hole, and the line was seen as broken in 26 of 32 cases. After surgery, the hole closed completely in 25 of 32 eyes; it disappeared from 14 of these 25 eyes and was replaced by a dark or clear disc in 11. In the other seven successful cases, its size shrank and its edge flattened but remained faintly visible. The hole remained unchanged in eight cases. Eccentric PRL became central in 28 of 32 cases. The scotoma disappeared in 23 of 32 cases. The line was seen as continuous in 24 of 32 cases. Complete anatomic and functional successes were achieved in 19 of the 32 cases of macular hole closure. CONCLUSION: The SLO examination allows accurate assessment of the anatomic and functional results of macular hole surgery. Various degrees of functional success were recorded, depending on the test used.

Electrophysiological exploration of visual function in mitochondrial diseases.

In a group of 10 children (ranging from 5 months to 15 years old) affected by diseases with mitochondrial dysfunction, 4 suffered from mitochondrial myopathy, 4 from mitochondrial encephalopathy and 2 from Friedreich's ataxia. The clinically detectable visual impairment consisted of 3 grey ocular fundi (the other 7 were normal) associated, in 2 subjects, with a mild nystagmus. Electrophysiological assessment, consisting of ERGs and flash VEPs, was systematically performed. The normal ERGs in all subjects confirmed the normal functioning of retinal electrogenesis. In contrast, the VEPs of 6 out of 10 subjects were modified: in 2 of the 4 subjects with mitochondrial myopathy, the VEPs had a hyperamplitude; in the 2 subjects with Friedreich's ataxia, the implicit time of the principal VEP peaks was increased, together with a hyperamplitude in 1 case; lastly, in 2 of the 4 subjects with mitochondrial encephalopathy, the VEPs were altered. These modifications reflected visual pathway conduction disorders with no clinical expression. Various underlying pathophysiological mechanisms possibly responsible for these modifications are discussed.

Contribution of scanning laser ophthalmoscopy to the functional investigation of subjects with macular holes.

A study was designed to validate a functional investigation performed with the scanning laser ophthalmoscope before surgery for macular holes in 12 eyes: The assessment included fundus examination, a functional examination resulting in evaluation of the preferred retinal lows, visual acuity and recording of visual evoked potentials. The preferred retinal locus was evaluated by presenting a small square area, and visual acuity was determined by means of calibrated figures. The visual evoked potentials were evoked by three alternating checkerboards (check size, 30', 2 Hz) centered over the hole and seen at an angle of 6.5 x 6.5 degrees, 2.5 x 2.5 degrees and 6.5 x 6.5 degrees with central exclusion of 2.5 x 2.5 degrees. The appearance of the fundus visualized by scanning laser ophthalmoscopy consisted of a clear central disk corresponding to the hole, surrounded by a very dark ring, associated with a second, less dark ring with unclear margins. Fixation was unstable in one case with a visual acuity of 20/70. In 11 cases, fixation was localized to the superior retina with a visual acuity superior to 20/70. The visual evoked potentials evoked by 6.5 x 6.5 degrees were discernible in all 12 eyes; visual evoked potential by annular stimuli were discernible in 11 cases. The 2.5 x 2.5 degrees stimulus evoked no response in eight cases, proving the area of the hole was nonfunctional. A response was recorded in the four other cases, where the dimension of the holes was less than 2 degrees. The results of this scanning laser ophthalmoscopic assessment demonstrated a precise evaluation of the residual macular function in the cases of full-thickness macular holes.

Focal visual evoked potentials generated by scanning laser ophthalmoscope in patients with age-related macular degeneration treated by perifoveal photocoagulation.

Perifoveal laser photocoagulation has been proposed for the treatment of subfoveal neovascular membranes in age-related macular degeneration. We evaluated residual function in seven eyes of six treated patients by means of transient focal visual potentials evoked with a scanning laser ophthalmoscope. The site of the preferred retinal locus was determined. The modulation of the helium-neon laser beam generated three tests (a homogeneous 6 x 6 degrees square--offset and onset--and two alternating pattern checkerboards 6 x 6 degrees and 2.5 x 2.5 degrees 60', 2 Hz) projected onto the preferred retinal locus. The focal visual evoked potentials were recorded. One eye had an unstable fixation with no discernible focal visual evoked potentials. The other six eyes had a stable fixation located in the superior retina, temporally for the right eyes and nasally for the left eyes. The homogeneous 6 x 6 degrees square evoked discernible responses in all six patients. The two checkerboards evoked discernible responses in five of six patients. These results were compared with those recorded in four controls in whom the three tests were projected onto the same retinal areas as in the patients. Evoked responses were more often recorded in the preferred retinal locus of the treated patients with age-related macular degeneration than in the corresponding retinal areas of the controls. The scanning laser ophthalmoscope allowed us to control the site of stimulation in the patients' and controls' retinas. These preliminary results suggest that there may be a functional plasticity of the visual system after therapeutic laser-induced central scotoma.

Is there a systematic location for the pseudo-fovea in patients with central scotoma?

The retinal location of preferential fixations of twenty-four patients with central scotoma were studied when reading digits projected onto their retina with a scanning laser ophthalmoscope. In the majority of cases the fixation was located on the left part, or the inferior part of the visual field relative to the central scotoma. The fact that the inferior visual field is used is coherent with the notion that the lower visual field is important for locomotion. However the preferential use of the left field appears contradictory with data showing superiority of visual faculties in the right visual field. This result may possibly be explained in relation to the need for left-to-right readers to monitor where their eyes have landed relative to the word previously fixated on the left.

Colored focal visual evoked potentials by cathode ray tube versus scanning laser ophthalmoscope.

We compared the focal visual evoked potentials obtained in 52 young subjects with normal vision, evoked by means of three alternating black/color checkerboards generated by a trichromic cathode ray tube (dominant wavelength, 514 nm; colorimetric purity, 0.45) and by means of a scanning laser ophthalmoscope (argon laser beam, 514 nm; colorimetric purity, approximately 1). These three checkerboards, with an area of 3.5 degrees x 3.5 degrees (stimulating the fovea), then with an area of 3.5 degrees x 3.5 degrees with a central exclusion of 1.5 degrees x 1.5 degrees (stimulating the perifoveola) and finally with an area of 1.5 degrees x 1.5 degrees (stimulating the foveola) were presented within a field (8 degrees x 8 degrees) of homogeneous luminance of 170 cd/m2 and 1500 cd/m2, respectively. Their check sizes were 30', with a reversal temporal frequency of 0.75 Hz. The transient focal visual evoked potentials recorded with these three stimuli generated by the two types of stimulators were clearly detected for at least 85% of subjects. Their characteristics (waveform, amplitude and culmination times of the different waves) were comparable, regardless of the stimulator used (cathode ray tube or scanning laser ophthalmoscope). These results suggest that, under these various conditions of luminance and colorimetric purity, the neurophysiologic circuits tested function in identical ways. The focal visual evoked potential signs, now clearly defined by means of stimuli generated by cathode ray tubes, therefore apparently can be applied to the focal visual evoked potential evoked by stimuli generated by the scanning laser ophthalmoscope.

A hereditary syndrome with retinopathy and ataxia or deafness in two consanguineous brothers.

Of two brothers born of Sephardic first cousin parents one presented with congenital neural deafness, nyctalopia, visual field loss, flat ERG, unintelligible speech and a shuffling gait, and the other with severe ataxia, severe decreased visual acuity, mild field loss, decreased ERG, dysarthric speech and high grade myopia. The diagnosis of Usher syndrome type 1 or 2 is discussed as well as the possibility that both brothers have different genetic disorders.

[Statistical results of 700 electrophysiologic tests (ERG) in patients without ophthalmologic manifestations treated with synthetic antimalarials for rheumatologic or dermatologic disease]. / Bilan statistique de 700 examens électrophysiologiques (ERG) chez des patients sans signe ophtalmologique traités par antipaludéens de synthèse pour maladie rhumatologique ou dermatologique.

737 adapto-electroretinograms are registered on patients treated by chloroquine for a rheumatoid arthritis (RA) or for a lupus. Their ophthalmological examinations are completely normal. In term of the cumulative doses, the statistical results of the electrological characteristics of the different waves of the ERG issued from white, red and blue stimulations show: a great stability of the latencies of the "a" and "b" waves; a gradual decrease of the "b" wave amplitudes for the RA; a gradual increase of the "b" wave amplitudes till a level dose reached between 800 and 900 g and then a decrease of the "b" wave amplitudes, for the lupus. We discuss the electrophysiological criterions for a beginning intoxication. As a standard, for the R.A., it seems that a certain amount of "b" wave amplitude decrease could be admitted but the "a" and "b" wave latencies must be very constant. For the lupus, the hyper normality or at least stability of the "b" wave amplitude can be admitted till a dose around 800 g, associated to a good stability of the "a" and "b" wave latencies. Beyond these statistically established limits a beginning intoxication should be suspected.

[Visual electrophysiology in 101 children with encephalopathy]. / Etude de l'électrophysiologie visuelle chez 101 enfants encéphalopathes.

The electrophysiological recordings (E.R.G. associated with C.V.E.P.) performed on 101 children suffering from encephalopathy of different origins demonstrate a trend towards retinal integrity for subjects with encephalopathy and no suspicion of acid-base disorders. However a functional macular deficiency is frequently observed in encephalopathy with suspicion of acid-base disorders (encephalopathy due to intracranial hypertension or cardio-vascular disorders or metabolic deficiencies with acid-base disturbance). In these cases, a common pathophysiological substratum with disturbance of the acute or chronic acid-base equilibrium has been assumed. Over a period of time, in fixed encephalopathy, the electrophysiological results reflect a real but slow maturation of the visual pathways.

Data processing software for electrophysiological visual exploration.

The software we have developed originated after careful study of a routine functional visual processing session. It has three objectives: (i) to have available a large library of data processing programs; (ii) to add to these electrophysiological results, automatically transferred into a file, a clinical record card, creating a personalized file for study of visual characteristics of each patient; (iii) to allow programs providing statistical studies, creation of groups based on the same clinical features and various comparisons between files or groups. The database now contains 5000 different files and the results of its use are very encouraging. Some results are presented, especially those of a study on multiple sclerosis. The goal of the operation is the creation, in the future, of an expert system.

[Retinal protection using glasses filtering short wave lengths in patients with hereditary degenerative diseases. First electrophysiologic results]. / Protection rétinienne par des verres filtrant les courtes longueurs d'ondes chez des patients atteints de maladies hérédo-dégénératives. Premiers résultats électrophysiologiques.

The electrophysiological action of the ORMA RT glasses filtering the short and middle wavelengths are exposed through the first results of this work by retinitis pigmentosa patients. In 90% of the tested patients A.E.R.G. and V.E.P. are improved.