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Biomedical subjects

J F Le Gargasson

Publications and source records attributed to J F Le Gargasson.

At least 19 recordsLinked to original sources
PubMed2000

'The-skipping' revisited in French: programming saccades to skip the article 'les'.

Three experiments were performed to verify O'Regan's (1979) [Perception & Psychophysics, 25 (6), 501-509] finding that in reading, the eye moves further forward when going towards the word 'THE' than when going towards a three-letter verb. The experiments were performed in French instead of English, and compared the plural article 'les' with different three-letter verbs. It was confirmed that the eye did indeed move about 1.5 letters further in the case of the article 'les'. Further investigation of the phenomenon suggested that the effect was present even when the prior fixation duration was short: Only when prior fixation was around 200 ms or less, and additionally when the eye started from a launch position that was far from the word, was there a suggestion that the 'les'-skipping effect disappeared.

Adult↗
PubMed1999

Effect of autologous platelet concentrate in surgery for idiopathic macular hole: results of a multicenter, double-masked, randomized trial. Platelets in Macular Hole Surgery Group.

OBJECTIVE: To evaluate prospectively the efficacy and safety of autologous platelet concentrate (APC) as an adjuvant in surgery for idiopathic macular hole. DESIGN: Multicenter, double-masked, randomized clinical trial. SETTING: Four university-based ophthalmology clinics. PARTICIPANTS: One hundred ten patients with stage 3 or 4 idiopathic full-thickness macular holes of less than 3 years' duration were randomized (53 eyes to the platelet group and 57 eyes to the control group). INTERVENTIONS: Standardized macular hole surgery versus surgery combined with injection of an APC. In all cases, the procedure consisted of three-port pars plana vitrectomy, posterior hyaloid separation, and nonexpansile fluid-gas exchange. After the fluid-gas exchange, patients were randomized to receive either injection of an APC or no adjunctive treatment. After surgery, patients were positioned face down for 12 days. Platelet counts showed that the concentrates contained a mean of 96.106 platelets (range, 82-102). MAIN OUTCOME MEASURES: Anatomic and functional evaluations were performed at 1, 3, and 6 months after surgery in a double-masked fashion by an independent observer. The main outcome was reapposition of the edge of the macular hole 1 month after surgery. Secondary outcomes were anatomic status at 3 and 6 months, changes in Early Treatment Diabetic Retinopathy Study score, and complications. RESULTS: One month after surgery, the anatomic success rate in the platelet group was 52 of 53 (98%; 95% confidence interval, 0.90-1.00) versus 47 of 57 (82%; 95% confidence interval, 0.70-0.91) in the control group (P = 0.009, Fisher's exact test; relative risk, 0.11; 95% confidence interval, 0.01-0.81). Visual acuity was not significantly different between the two groups at any timepoint. There were no complications specifically attributable to the platelet injection. CONCLUSION: Injection of APC improved significantly the anatomic success rate of surgery for idiopathic macular holes of less than 3 years' duration, but postoperative visual acuity of the platelet group was not statistically different from the control group.

Aged↗
PubMed1998

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.

Fixation, Ocular↗
PubMed1997

Scanning laser ophthalmoscope imaging of fluorescein-labelled blood cells.

PURPOSE: To demonstrate the feasibility of a technique for the visualization by scanning laser ophthalmoscope (SLO) of fluorescein-labelled autologous leukocytes and platelets in retinal vessels. METHOD: Individual blood samples from rats and rabbits were centrifuged to isolate platelets and leukocytes, then passively labelled with fluorescein and reinjected into the same animal. An SLO was used to visualize and record cell displacement in the retinal circulation. Labelled platelets were analysed by flow cytometry. RESULTS: By SLO, platelets appeared as a heterogeneous particle flow, and individual leukocytes appearing as brighter spots could easily be traced. Flow cytometry showed that after labelling platelets were well individualized and their size was slightly increased. CONCLUSION: Circulating blood cells can be visualized in retinal vessels by a simple method consisting of passive labelling of autologous platelets and leukocytes by fluorescein. No platelet toxicity was detected. This method could be applied to the study of blood cell movement in human retinal vascular diseases.

Animals↗
PubMed1997

Late reopening of successfully treated macular holes.

BACKGROUND: Most idiopathic macular holes can be closed by a surgical procedure combining vitrectomy, posterior hyaloid ablation, and fluid-gas exchange followed by postoperative positioning. Reopening of closed macular holes has been reported, but its frequency is not known. Here the incidence of reopening after successful macular hole surgery is reported. METHODS: 77 consecutive cases of idiopathic macular holes operated with autologous platelet injection between July 1993 and October 1995 were reviewed. The procedure consisted of three port vitrectomy, posterior hyaloid removal, nonexpansile fluid-gas exchange, and autologous platelet injection followed by face down positioning. The incidence of reopening was analysed in the cohort of the 72 anatomical successes. RESULTS: Mean follow up was 12.3 months. The macular hole reopened in five eyes of five patients (five out of 72 patients, 6.9%), in four cases after cataract extraction. In four cases too, an epiretinal membrane was noted, either clinically or during reoperation, and fluorescein leakage in the macular area was present in two cases. Three of the five cases of reopening were reoperated and all three were anatomical successes. CONCLUSION: Late macular hole reopening occurred in five out of 72 patient, and in four cases after cataract surgery. The presence of an epiretinal membrane around the hole in four of them suggested that tractional forces were responsible for the reopening. Reoperation, performed in three cases, again closed the macular holes.

Aged↗
PubMed1995

Autologous platelet concentrate for the treatment of full-thickness macular holes.

BACKGROUND: To improve the anatomic success rate in the surgery of full-thickness macular holes, we tested, in a prospective pilot study, the effects of autologous platelet concentrate deposited on the macula at the end of surgery. METHODS: Two consecutive groups of patients were compared. Twenty eyes (group 1, mean symptom duration 11 months) were operated on with injection of an autologous platelet concentrate on the macula after fluid-gas exchange. Another 20 eyes (group 2, mean symptom duration 11 months) were subsequently operated on without autologous platelet concentrate. For all stage 3 holes, posterior hyaloid was detached en bloc at the level of the optic disc. The patient was left supine for 24 h after surgery, and then remained face down for 10 days. RESULTS: In group 1, 19 cases were an anatomic success, i.e. there was flattening of the retina surrounding the hole and reattachment of the edge of the hole to the retinal pigment epithelium; in 9 cases the hole was even undetectable. Final visual acuity was 0.5 or more in 9 eyes, and 0.4 or more in 14. Visual acuity improved by two lines or more in 17 of the 19 successfully operated eyes. In group 2, only 13 cases were an anatomic success. The functional results for the successfully operated eyes were identical to those of group 1. CONCLUSION: These results strongly suggested that autologous platelet concentrate could significantly improve the success rate in macular hole surgery and led us to begin a comparative, prospective, randomized trial.

Adult↗
PubMed1995

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.

Adolescent↗
PubMed1995

Alcohol consumption and visual contrast sensitivity.

Visual contrast sensitivity (VCS) was measured in 30 alcoholic patients and 52 controls. The results showed a significant reduction in VCS for all the spatial frequencies. The mean reduction for all spatial frequencies was 2.49 dB below the level of the control group. Optimal sensitivity corresponded to a lower spatial frequency in patients than controls, i.e. 1 cycle/degree (c/d) versus 2 c/d. Curves for VCS were normal for five patients. Abnormalities in VCS were suggestive of optic nerve dysfunction for 15 patients (50%), which were probable in seven cases (23%) and possible in eight others (27%). For 10 subjects, the abnormalities were indicative of ametropia. Daily alcohol intake and daily tobacco consumption were not significantly different in the patients who displayed VCS abnormalities, reflecting alcohol-tobacco amblyopia, from those who did not. The presence of higher gamma-glutamyl transpeptidase and mean corpuscular volume levels in patients who had VCS abnormalities indicative of alcohol-tobacco amblyopia suggests that alcohol consumption is involved in the development of these abnormalities.

Adult↗
PubMed1994

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.

Aged↗
PubMed1994

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.

Aged↗
PubMed1994

Eye fixations near corners: evidence for a centre of gravity calculation based on contrast, rather than luminance or curvature.

Subjects scanned line drawings of polygons in order to count the number of corners. The positions their eyes fixated were studied as a function of the size of the angle and whether the apex of the angle was present or absent. The results showed that the eyes tended to land at a position near the centre of gravity of the corner configurations. The observed landing positions were coherent with the hypothesis that the centre of gravity was calculated within an attentional spotlight centered on the apex of the corners, and that the calculation was based not on the total luminance distribution, nor on the distribution of energy in a neurophysiologically motivated curvature detector, but simply on the basis of a contrast detector.

Adult↗
PubMed1993

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.

Adult↗
PubMed1993

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.

Adult↗
PubMed1990

[Visual electrophysiology in 101 children with encephalopathy].

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.

Brain Diseases↗
PubMed1984

[Evoked potentials and structured and colored stimuli].

After a historical account and a brief description of the techniques of signal analysis used in their laboratory (visual evoked potentials (VEPs) with statistical calculations, Fast Fourier Transform, correlation function), the authors present the experiments they undertook concerning colored stimulations. These experiments were carried out in 3 steps: colored stimulations on a cathode-ray screen, with constant luminance, concerning 8 healthy volunteers (72 VEPs analyzed); colored stimulations on a 'structured' screen (pattern reversal), concerning 31 healthy volunteers (186 VEPs analyzed); colored and pattern stimulations on a new cathode-ray stimulator built in the 'Centre National des Arts et Métiers' enabling both preceding types of stimulations with increased reliability and offering new possibilities of stimulation (variation of contrast, luminance or chromaticity precisely controlled) with various patterns in the background. The results evidence two different groups of electrophysiological responses, distinctly related to the presence or absence of a morphological structure in the stimulation. As well as this, a significant increase in latencies is observed with blue stimulations.

Adult↗
PubMedDate not supplied

[Statistical results of 700 electrophysiologic tests (ERG) in patients without ophthalmologic manifestations treated with synthetic antimalarials for rheumatologic or dermatologic disease].

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.

Adolescent↗