[Functional amblyopia: a functional MRI evaluation of the visual cortex response after treatment]. / Amblyopie fonctionnelle : évaluation en IRM fonctionnelle de la réponse corticale visuelle après traitement.

PURPOSE: Functional MRI evaluation of the cortical response in treated amblyopic patients. MATERIAL AND METHODS: Clinical and functional MRI exploration of ten patients, seven men and three women aged from 21 to 59 years, with strabismus management during childhood. Functional evaluations were performed on a 1.5 Tesla MR device, with four monocular functional sessions, two stimulations per eye. Alternating rest and active phases displayed still and flickering black and white checkerboards with spatial and temporal frequencies of 1 degree/8Hz and 15'/4Hz. Anatomical realignment and statistical analysis were performed using SPM99 (Statistical Parametric Mapping) to compare the four sessions in individuals. RESULTS AND DISCUSSION: In patients presenting a visual acuity of the amblyopic eye less than 0.7, stimulation of this eye induced lower response in V1, V3, and V5 in comparison with the contralateral eye stimulation. Unexpectedly, in patients recovering normal or subnormal acuity, the amblyopic eye gave comparable or enhanced response in these areas. Additional response was found in the secondary visual cortex, the cuneus, the lingual gyrus, and in parietal, frontal, and orbitofrontal areas. These results suggest a variation in cortical response depending on the efficacy of the treatment. Recovered amblyopic eye, even with acuity less than the contralateral eye, may induce a reinforced cortical sensitivity to visual stimulus. Secondary visual areas may contribute to an attentional process in image perception and analysis. Cortical plasticity may be observed several years after amblyopia treatment. CONCLUSION: Our study substantiates the importance of an effective and early treatment of functional amblyopia, inducing cortical plasticity with reinforced attention and sensitivity to visual perception.

[Electrophysiological monitoring of epileptic patients treated with Vigabatrin]. / Surveillance électrophysiologique des patients épileptiques traités par Vigabatrin.

Vigabatrin is a GABA mimetic antiepileptic agent that has been used for 10 years in cases of epilepsy that resist other treatments. Since 1997, concentric visual field defects have been reported. Before any visual symptom complaint, they quickly become irreversible and highly disabling. To prevent this visual impairment, the monitoring protocol must be defined with reliable and well-supported tests, so that patients treated with Vigabatrin can be regularly monitored. Our purpose was to know if EOG impairments were frequent, if their severity was proportional to visual impairment, and if the Arden ratio could be a predictive criterion of Vigabatrin toxicity. Seventy-two patients treated with Vigabatrin for 2-10 years were examined, and EOG results were compared with a normal population EOG and then the patient's visual field. The monitoring protocol proposed includes EOG, which seems to be the most sensitive and specific diagnostic tool for screening Vigabatrin-treated patients.

[Ophthalmologic prevention of chloroquine and hydroxychloroquine induced retinopathy]. / Prévention ophtalmologique de l'intoxication rétinienne induite par les antipaludéens de synthèse.

INTRODUCTION: Antimalarial drugs induce severe retinal toxicity. The aims of this study were to evaluate the strategy of screening clinical and preclinical intoxication due to antimalarial agents in two centres of reference and to describe the results of ophthalmologic examination. PATIENTS AND METHODS: Patients referred for ophthalmologic evaluation in connection with antimalarial agents therapy in the Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts from October 1999 to December 2000 and in the Hôpital Lariboisière from January 1995 to December 1998 were investigated. A retrospective review of results of ophthalmologic examination, electroretinogram, electro-oculogram, colour vision test and central visual field was conducted to assess retinal intoxication. RESULTS: Among 705 patients recruited in the Centre des Quinze-Vingts, 10 out of 133 who were never treated had an electrophysiological contra-indication to the treatment. Among the 572 other patients, 31 presented with preclinical intoxication (5.4 p. 100) and 8 other patients presented with clinical intoxication. Among 925 patients recruited in the Hôpital Lariboisière, 37 presented with preclinical intoxication (4 p. 100) and four patients presented with clinical intoxication. DISCUSSION: The antimalarial drugs clinical intoxication is rare but nevertheless real. Screening for preclinical intoxication can prevent the evolution toward irreversible retinal intoxication. Diagnosis of preclinical intoxication is established through the confrontation of results of different tests and their evolution. The multifocal electroretinogram remains to be evaluated. CONCLUSION: Ophthalmologic monitoring including funduscopy, should be recommended at least once a year. Visual field seems to become interesting in the screening. Electroretinogram and electro-oculogram remain useful quantitative and obvious tests. A prospective study to assess the optimal way to prevent retinal intoxication is mandatory.

[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.

[Acute optic neuritis: clinical and MRI prognostic factors. Study of fifty patients]. / Neuropathie optique inflammatoire aiguë: facteurs pronostiques cliniques et IRM.

The objective of this study was to evaluate the risk of visual outcome after acute optic neuritis (ON) in relation to clinical and MRI findings. Fifty cases of acute ON within one month were retrospectively studied. MRI with Short Tau Inversion Recovery (STIR) sequence of the optic nerve were obtained with a median time onset of 9 days after ON. Mean age of patients was 32.8 years, mean initial visual acuity was 3/10 and orbital pain was present in 86 percent100 of patients. The STIR sequence revealed lesion in 88 percent 100 of acutely symptomatic optic nerves. An initial low visual acuity (less than 2/10), the absence of orbital pain and involvement of the intracanalicular portion of the optic nerve on STIR sequence were statistically correlated with a poorer visual outcome (respectively p=0.0041, p=0.035 and p=0.011).

[Exploration of retro-chiasmatic visual pathways in human albinism]. / Exploration des voies optiques rétro-chiasmatiques chez l'albinos.

PURPOSE: Several research studies have explored the abnormal crossing of the retinogeniculate and geniculocortical optic pathways in human albinos. This prospective study has dealt with visual evoked potentials (VEPs) of human subjects to identify the percentage of albinos with asymmetric VEPs. PATIENTS AND METHODS: A series of 16 albino patients ranging in age from 6 to 37 years were examined. They had measurable visual acuity, with or without nystagmus. Diffusion of flash stimuli not allowing selective study of the two visual pathways (direct and crossed), two stimulation patterns were used for VEP recordings: monocular full open field then hemi-field stimulation to isolate the activity of each visual pathway. ANALYSIS: In the normally pigmented subject, fibers derived from the nasal half of the retina of each eye decussate at the chiasma, while temporal retinal fibers are uncrossed and project to the ipsilateral hemisphere. In albinos, the majority of temporal retinal fibers subserving the nasal field (from fixation to an eccentricity of about 20 degrees ) anomalously cross with the nasal retinal fibers. Therefore with monocular stimulation, the evoked visual response should be obtained only in the contralateral hemisphere. The asymmetry, morphology and latency for the first major positive peak and the amplitude of the VEP were examined and compared with the normal population. CONCLUSION: We managed to demonstrate the characteristic VEP asymmetry only in 3 out of the 16 patients. The results presented herein lead to question the absolute validity of VEP abnormality in diagnosis of albinism for clinical purposes.

[Electrophysiologic diagnosis of 2 psycho-visual syndromes: Balint syndrome and cortical blindness. A propos of a case of Benson progressive posterior atrophy]. / Diagnostic électrophysiologique de deux syndromes psycho-visuels: syndrome de Balint et cécité corticale. A propos d'une observation d'atrophie postérieure progressive de Benson.

Cortical blindness and Balint's syndrome are two pathologies not well-known. It seems therefore interesting to report a typical patient case, suffering from Benson's posterior cortical atrophy, who presented successively both syndromes. The Balint's syndrome, which results from a bilateral parieto-occipital junction brain injury, and combines clinically a specified triad defects: a spatial disorder of attention, a psychic paralysis of gaze and an optic ataxia. The cortical blindness, which is caused by bilateral damage of the occipital lobes (Broadman area 17). Electrophysiologically, the abolition of short-latency components of visual evoked potentials and the presence of long-latency potentials are recorded. Visual strategy and visual evoked potentials are thus the only objective examinations allowing to diagnose and follow up these patient's evolution. In any case, an adequate visual rehabilitation has to be carried out in order to help the patient recovering his autonomy.

[Retrochiasmatic lesions in multiple sclerosis. Demonstration by visual evoked potentials. Correlation with magnetic resonance imaging]. / Lésions rétrochiasmatiques dans la sclérose en plaques. Mise en évidence par les potentiels évoqués visuels. Corrélations avec l'imagerie par résonance magnétique.

Monocular stimulation of each visual hemifield can show an interhemispheric asymmetry of VEP. Validity of this test needs a reproducibility of responses and exclusion of stimulation induced by eye movements. In a prospective study of 22 MS cases, it appeared that interhemispheric asymmetry was a criterion of dissemination is space and had a good diagnostic value: MS became clinically definite in 10/12 cases; in 10 other cases in which a correlative MRI-VEP study was possible, there were disseminated high signal areas in T2 weighted sequences on hemispheric MRI. In 7/10 cases, these areas were located on retrochiasmatic visual pathways. With MRI, VEP are the most performant tests for early diagnosis in MS. Technical progress will improve its fiability. Prospective correlative clinical, electrophysiological and MRI studies are necessary on a larger number of MS patients.

Latencies of visually guided saccades in unilateral hemispheric cerebral lesions.

Latencies of lateral visually guided saccades were studied in 60 patients without hemianopia who had unilateral focal lesions clearly visible on computed tomographic (CT) scan that were variously located in both cerebral hemispheres. Significantly asymmetrical latencies were found in 29 patients whose lesions had damaged the deep and posterior frontal region near the corpus callosum and/or, just inferior to this region, the anterior part of the internal capsule. In the 31 other patients, including those with lesions of the frontal eye fields (FEF), latencies were not significantly asymmetrical and the lesions spared the entire region just described. These topographical features suggest that the asymmetry of latencies is due to damage in a certain portion of the efferent pathways descending from the FEF. A significant increase in bilateral latency was observed in most patients whose lesions had damaged the posterior part of the parietal cortex and/or the underlying white matter. The parietal lobe could therefore exert an excitatory bilateral action on the triggering of visually guided saccades, probably mediated via the superior colliculus. A significant decrease in the bilateral or ipsilateral latency was often found in patients whose lesions had damaged the FEF or the underlying white matter. The frontal lobe could therefore exert a predominantly inhibitory bilateral action on this triggering, probably also mediated via the superior colliculus. However, an increase in contralateral latency in some patients with subcortical frontal lesions indicates that the FEF also probably have an excitatory action. This action could be transmitted directly (or indirectly via the superior colliculus) to the reticular premotor structures by tracts decussating partly through the corpus callosum.

[Study of colour vision and visual evoked responses in multisclerosis diagnosis (author's transl)]. / Etude de la vision des couleurs et des potentiels évoqués visuels dans le diagnostic de la sclérose en plaques.

In a patient with suspected Multisclerosis (M.S.), the discovery of a lesion in the anterior optic tracks is of considerable diagnostic importance. If none of the classical clinical signs of optic neuritis can be found, the study of visual evoked responses (VER) and of colour vision is useful evidence for diagnosis. In a population of 102 patients having "possible", "probable" or "confirmed" M.S, we have compared the information provided by both these methods. 27 patients had MS with a known optic neuritis: the VER and colour vision of all of them was altered, either unilaterally or bilaterally. 75 patients had "possible" or "probable" MS without a history of optic neuritis. For 34,7%, the discovery of a dyschromatopsia showed a lesion in the optic nerve. In 68%, only the increased latency in VER demonstrated an optic neuritis. It should be noted that for all the patients with "probable" or "confirmed" MS, the VER latency was increased. The study of colour vision is therefore in our opinion, an excellent way of investigating anterior optic tracks lesions. When the study of colour vision is not sufficient, the recording of VER is a reliable technique and a very valuable acquisition in neuro-ophthalmology.