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Biomedical subjects

M Bonnet

Publications and source records attributed to M Bonnet.

At least 55 records · Page 3Linked to original sources
PubMed1996

-Choroidal detachment associated with rhegmatogenous retinal detachment: a risk factor for postoperative PVR?.

PURPOSE: To determine whether preoperative choroidal detachment associated with primary rhegmatogenous retinal detachment is an independent risk factor for postoperative PVR. MATERIAL AND METHODS: One hundred eighty nine primary rhegmatogenous retinal detachments in 187 consecutive patients, initially operated on by the same surgeon, were enrolled in a prospective study. Ten eyes showed preoperative choroidal detachment associated with retinal detachment. Owing to the small number of eyes with preoperative choroidal detachment, we conducted the statistical analysis using the calculation of relative risk. RESULTS: The correlation between preoperative choroidal detachment and preoperative PVR grade C-D was statistically significant (RR: 9.03; confidence interval: 2.91-28). Postoperative PVR occurred, or recurred, in one of the 10 eyes with preoperative choroidal detachment (10%), and 10 of the 179 eyes with no choroidal detachment (5.58%). The difference between the two groups is not statistically significant (RR: 1.79; confidence interval: 0.25-12.64). All eyes which developed postoperative PVR showed one or two recognized independent risk factors for postoperative PVR (preoperative PVR grade C-D and/or retinal tears > or = 90 degrees). CONCLUSION: With the treatment modalities used in the present series (preoperative and postoperative steroids, and vitreoretinal microsurgery) preoperative choroidal detachment associated with primary rhegmatogenous retinal detachment no longer appears to be an independent risk factor for postoperative PVR.

Adult↗
PubMed1996

[Retinal detachment caused by macular holes in patients with severe myopia: results of intravitreal injection of pure C3F8].

PURPOSE: To evaluate the long-term anatomic and visual results of intravitreal injection of pure C3F8 in the management of retinal detachments due to macular holes in myopic eyes. MATERIALS AND METHODS: Twenty one highly myopic eyes (19 patients) with retinal detachments due to macular holes were initially managed by intravitreal injection of pure C3F8. The postoperative follow-up ranged from 6,5 to 45 months (median: 27.5 months). RESULTS: Total retinal reattachment was achieved in 16 eyes (76.2%). Anatomic success was obtained with a single C3F8 injection in 15 eyes, and two injections in one eye. The 5 eyes which failed to reattach after gas injection underwent reoperation using choroidal irritation in the macular area associated with gas injection. The retina was reattached in all eyes. Eleven of the 16 eyes (68.7%) in which the retina was reattached solely with intravitreal gas injection had a nearly normal final near reading visual acuity. In contrast, none of the eyes reattached with the use of choroidal irritation had measurable final visual acuity. CONCLUSION: The results achieved in the present series of patients confirm that intravitreal injection of pure C3F8 is a valuable alternative in the management of retinal detachments due to macular holes in myopic eyes. We recommend this treatment approach as the initial surgical procedure, since more than half of eyes successfully operated on recover useful central vision.

Adult↗
PubMed1996

[Has the incidence of postoperative PVR in rhegmatogenous retinal detachment decreased?].

PURPOSE: To determine whether the incidence of severe postoperative PVR in primary rhegmatogenous retinal detachment has decreased over the last twelve years. MATERIALS AND METHODS: We prospectively evaluated 595 eyes of 554 consecutive patients with primary rhegmatogenous retinal detachment, referred before any failed attempt to reattach the retina, managed by the same surgeon between March 1983 and December 1994. The eyes were divided into two consecutive series: 275 eyes operated on from March 1983 through February 1988 (series no. 1), and 320 eyes operated on from February 1988 through December 1994 (series no. 2). We conducted univariate and multivariate statistical analyses to compare the incidence of postoperative PVR in the two consecutive series. RESULTS: The overall incidence of postoperative PVR was 8.72% (24/275 eyes) in series no. 1, versus 2.81% (9/320 eyes) in series no. 2 (p < 0.01). The incidence of postoperative PVR in retinal detachments due to atrophic holes in lattice degeneration, oral dialyses, and macular holes in myopic eyes, was nil in both series. The incidence of postoperative PVR in retinal detachments due to horseshoe tears with mobile posterior edges was 1.16% (1/86 eyes) in series no. 1, and 0% (0/109 eyes) in series no. 2. The incidence of postoperative PVR in retinal detachments associated with horseshoe tears with curled posterior edges was 21.15% (11/52 eyes) in series no. 1 versus 3.2% (3/93 eyes) in series no. 2 (p < 0.001). The incidence of postoperative PVR in giant tears was 35.5% (11/31 eyes) in series no. 1. and 14.7% (5/34 eyes) in series no. 2 (chi square = 3.77; at the limit of significance). The incidence of postoperative PVR in retinal detachments du to paravascular tears of the post-equatorial region in myopic eyes was 25% (1/4 eyes) in series no. 1, and 14% (1/7 eyes) in series no. 2. CONCLUSION: In our own experience, the incidence of postoperative PVR in primary rhegmatogenous retinal detachment has decreased at a statistically significant level since 1988. We believe that the decreased incidence of postoperative PVR in our most recent series is mainly related to the use of laser photocoagulation retinopexy rather than cryopexy in the management of high risk eyes (retinal detachments associated with horseshoe tears with curled posterior edges, and giant tears).

Adolescent↗
PubMed1995

Multi-slice, breathhold imaging of the lung with submillisecond echo times.

The signal from the lungs is heavily attenuated by T2 and T2 decay in standard MR images of the thorax. The authors utilized the capabilities of a prototype fast gradient system to develop a multi-slice gradient echo sequence that can obtain images with an echo time of 0.7 ms. Images acquired in a single breath-hold are free from respiratory motion artifacts and clearly display signal from lung parenchyma. The use of fast gradients makes short echo times possible without the use of nonstandard RF pulses and spatial encoding techniques and their associated limitations.

Artifacts↗
PubMed1995

Surgical risk factors for severe postoperative proliferative vitreoretinopathy (PVR) in retinal detachment with grade B PVR.

BACKGROUND: Previous studies have shown that grade B proliferate vitreoretinopathy (PVR) is a considerable risk factor for the development of severe postoperative PVR. We conducted a prospective study to elucidate which surgical procedures used in retinal detachment management may stimulate the PVR process in such eyes. MATERIALS AND METHODS: The study included 156 eyes of 152 consecutive patients with rhegmatogenous retinal detachment complicated by grade B PVR referred before any failed surgery and operated on between 1983 and 1993. The parameters evaluated by multivariate statistical analysis included the cumulative circumferential extent of the retinal tears, the extent of the scleral buckle, gas injection, vitrectomy, the method used for retinopexy, and the time of surgical management during the period of the study. RESULTS: The incidence of severe postoperative PVR was 25.8% in eyes managed with cryotreatment versus 2.2% in eyes managed with argon laser photocoagulation (P = 0.001). The rate of severe postoperative PVR was not influenced by the other surgical variables. CONCLUSION: We conclude that cryotherapy may be a risk factor for the development of severe postoperative PVR in retinal detachments associated with grade B PVR.

Adolescent↗
PubMed1995

Programming the duration of a motor sequence: role of the primary and supplementary motor areas in man.

Event-related potentials were recorded in a reaction time (RT) paradigm, where the duration of a learned interval (either 0.7 s or 2.5 s) delimited by two brief button-presses was to be accurately controlled. A preparatory signal (PS) either did not give or gave prior information concerning the duration of the following response (neutral condition or primed conditions, respectively). In the latter case, the information was either validated (valid condition) or invalidated (invalid condition) by the response signal (RS). When duration was not known in advance (invalid and neutral conditions), RTs were longer before a response of short than long duration. This difference was not found under the valid condition. During the preparatory period (PP), the amplitude of the contingent negative variation (CNV) was larger when the duration was primed than when it was not. A larger CNV appeared when the PS primed a short rather than a long duration. This effect occurred in the early part of the PP over the supplementary motor area (SMA) and in its latest part over the primary motor area (MI). The RT and the electrophysiological pattern were interpreted as revealing the occurrence of programming operations regarding the temporal dimension of the response. The time course of the CNV over the SMA and MI suggested that these two areas were hierarchically organized. Between the RS and the onset of the response, differences probably related to programming effects were still found over MI: the activities were larger under the valid than under the neutral condition. However, no sign of deprogramming (expected in the invalid condition) was observed: similar amplitudes were found under the neutral and invalid conditions. Deprogramming operations seemed to be postponed during response execution where the invalid condition evoked larger activities than the two other conditions over the SMA. Finally, MI but not the SMA yielded a Bereitschaftpotential before the second press ending the response (i.e., during response execution). These results suggest that the duration of a motor response can be a part of the motor program and that the SMA plays a major role in programming processes but not in response execution, contrary to MI.

Algorithms↗
PubMed1995

Modulation of spinal reflexes: arousal, pleasure, action.

The human startle reflex is reliably modulated by the affective valence of foreground pictures, with larger reflexes elicited when viewing unpleasant relative to pleasant scenes. If this modulation is due to priming of the defensive startle reflex by an aversive foreground, a different pattern should occur for a reflex that is not inherently defensive in nature. In the current study, affective modulation was investigated using the spinal tendinous (T) reflex, which is well documented as sensitive to differences in arousal and is involved in actions that are both appetitively defensively motivated. As such, T reflexes elicited during unpleasant pictures were not expected to be augmented relative to those elicited in the context of pleasant pictures. Results showed that T reflexes were facilitated during processing of arousing stimuli-either pleasant or unpleasant relative to low-arousal neutral materials. These effects of emotional stimuli on T-reflex amplitude are consistent with hypothesis that motivational priming underlies affective reflex modulation.

Adult↗
PubMed1995

[Myasthenia induced by tiopronin in the treatment of rheumatoid arthritis].

Myasthenia gravis (MG) is a well known side-effect of D-Penicillamine used in the treatment of rheumatoid polyarthritis. Tiopronin is another drug available in France, which can also induce MG. Drug-induced MG are characterized by frequent involvement of facial and oropharyngeal muscles. Moreover, the generalization is scarce and the outcome always quite good. No thymoma is present, anti-acetylcholine receptors antibodies are often highly positive. Furthermore, some HLA phenotypes are most frequently found among patients with drug-induced MG suggesting a genetic predisposition. This observation underlines the interest of careful management of patients treated by tiopronin.

Aged↗
PubMed1994

NMR study of collagen-water interactions.

A proton magnetic resonance study of different cross-linked collagens was performed as a function of water content and temperature. Collagens from three connective tissues (calf, steer, and cow) were chosen according to the different number of nonreducible multivalent cross-links, which increases during the life of animal. Samples were hydrated under five well-defined water activities (Aw) ranging from 0.44 to 0.85. The transverse and cross-relaxation times of water protons were studied as a function of temperature from -20 up to 100 degrees C. From the temperature dependence of relaxation rates, the dynamics of water molecules can be described according to different processes: exchange of protons at the higher temperatures and dipole-dipole interactions that prevail at the lower temperatures. The exchange processes are analyzed as a function of the residence lifetime of water molecules at the protein interface and of the transfer of spin energy from water protons to macromolecule protons. The proton dipole-dipole interactions are related to the relaxation parameters of protein and water protons. All the relaxation parameters showed specific behavior for the 0.44 water activity for every tissue. The collagen tissue from calf also showed distinct behavior in comparison with other tissues.

Animals↗
PubMed1994

Radiation therapy in proliferative vitreoretinopathy. A prospective randomized study.

In a prospective study of the effect of postoperative radiation therapy for the prevention of reproliferation of membranes and recurrent proliferative vitreoretinopathy (PVR) two similar groups of patients with retinal detachment and PVR grade D1 to D3 in one eye were compared. Half the eyes (30) received a total dose of 3000 cGy after surgery; the other half remained untreated. After a follow-up of 6 months and 14 months or more (maximum 36 months) the anatomical and functional results of each group were compared. After 6 months in the unirradiated group 57% (17/30) remained attached and 43% (13/30) had detached again. In the irradiated group 63% (19/30) were attached and 37% (11/30) had detached. However, there was no statistically significant difference between the two groups (P = 0.479, Fisher's Exact Test). After 14 months the number of cured and uncured eyes remained the same in the unirradiated group, while in four of the eyes in the irradiated group a later onset of reproliferation and detachment occurred (after 7, 8, 12 and 14 months, respectively). A final cure rate of 57% (17/30) was achieved in the unirradiated group and a 50% (15/30) cure rate in the irradiated group. Thus the failure rate was 43% (13/30) in the unirradiated group and 50% (15/30) in the irradiated group (P = 0.473, Fisher's Exact Test). No side effects from the radiation were observed in any case and no radiation retinopathy occurred during an observation period of up to 3 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

A new three-dimensional culture of human keratinocytes: optimization of differentiation.

Many attempts have been made to obtain reconstructed human epidermis comprised of keratinocytes and extracellular-matrix constituents (essentially collagen) in the presence or absence of fibroblasts. A simple model of cultured human keratinocytes, grown at the air-liquid interface of a noncoated artificial membrane, has been developed. This culture system offers many advantages: easy control of environmental factors and routine examination using optical or electronic microscopy, immunohistochemistry and indirect immunofluorescence techniques. This model enables the analysis of well-known differentiation markers and also integrins, a family of cell-surface molecules involved in cell-cell and cell-extracellular matrix interactions, whose receptors are expressed on all basal keratinocytes. In our culture system, the expression of the different integrin subunits (alpha 2, alpha 3, alpha 5, alpha 6, beta 1) was studied as a function of the differentiation state in two different media (K-SFM or DMEM/Ham's F12) supplemented with 5% fetal calf serum and adjusted to 1.5 mmol/L calcium. The most significant data are the preponderant expression of the alpha 2 and alpha 3 subunits in the basal and suprabasal layers, with membrane expression differing according to the culture medium; terminal differentiation was obtained in DMEM/Ham's F12. The use of membrane inserts represents a significant technological advance in culturing keratinocytes and is an easy-to-handle and valid model for determining the influence of physiological or pharmacological factors on cell proliferation or differentiation.

Cell Adhesion↗
PubMed1994

Macular changes and fluorescein angiographic findings after repair of proliferative vitreoretinopathy.

PURPOSE: To evaluate the status of the macula after surgical treatment of proliferative vitreoretinopathy (PVR). METHOD: Biomicroscopic and fluorescein angiographic examination of the macula was performed in 58 eyes of 58 patients 6 to 7 months after complete gas absorption for rhegmatogenous retinal detachment complicated by PVR (grade C1 to D3). RESULTS: Macular changes were found in 46 eyes (79.3%), and included: cystoid macular edema (30 eyes; 51.7%), epiretinal membranes distant from the macula (3 eyes; 5.1%), macular pucker (7 eyes; 12%), subretinal membranes (5 eyes; 8.6%), and subretinal pigment dispersion (5 eyes; 8.6%). In five eyes, two distinct changes were found. Optic dye leakage occurred in 4 eyes (6.8%). CONCLUSION: Biomicroscopic and fluorescein angiographic examination of the macula can be used to determine why eyes in which rhegmatogenous retinal detachment complicated by PVR is successfully repaired do not achieve good recovery of vision. Spontaneous improvement or disappearance of postoperative cystoid macular edema, with late improvement in visual acuity, may occur in a small number of patients.

Adolescent↗
PubMed1994

[Pilot study of transscleral light coagulation of retinal breaks using diode laser].

PURPOSE: We conducted a pilot trial to evaluate the efficacy and safety of transscleral diode laser photocoagulation in the management of retinal breaks. MATERIAL AND METHODS: Fourteen patients (14 eyes) were enrolled in the study. Twelve patients showed opaque media which prevented transpupillary argon laser photocoagulation (10 eyes) and/or a retinal detachment after previous failed surgery (3 eyes), and/or retinal tears with a curled and fixed posterior edge (6 eyes). Twenty five retinal breaks were treated in the 14 eyes (7 breaks in attached retina and 18 in detached retina). RESULTS: A satisfactory retinochoroidal scar with permanent sealing of the retinal breaks was achieved in all eyes. The retina was attached in all eyes. The follow-up ranged from 2 to 12 months. Ten patients had a minimum 6 month-follow-up. Overtreatment attributed to technical mistake occurred in two eyes. It has no adverse effect on the final result. CONCLUSION: Transscleral diode laser photocoagulation of retinal breaks is efficacious and safe. It is a valuable alternative to cryo treatment in eyes at high risk of postoperative PVR and/or when argon laser photocoagulation cannot be used, and/or in retinal detachments after previous failed surgery.

Adolescent↗
PubMed1994

[Retinal detachment after surgery of congenital cataract].

We conducted a retrospective study of retinal detachments after congenital cataract surgery managed during the last twelve years so as to determine whether the surgical prognosis has been improved by the use of vitreoretinal microsurgery. The study included 25 eyes of 23 consecutive patients. The time interval between cataract surgery and the onset of retinal detachment ranged from 1 month to 46 years. It was 10 to more than 30 years in 60% of patients. Fourteen patients (60.8%) were over 26 years old. Nine eyes (36%) showed PVR grade B to D3. Preoperative fundus examination was hindered by anterior segment changes secondary to cataract surgery in 18 eyes. Microsurgical management included reconstruction of the anterior segment via the pars plana in 7 eyes, vitrectomy in 10 eyes, gas injection in 15 eyes and the use of liquid perfluorocarbon in 1 eye. Anatomic success with at least a six month-follow-up was achieved in 22 eyes (88%). It is concluded that the surgical prognosis of retinal detachment after congenital cataract surgery has been improved by modern vitreoretinal microsurgery.

Adolescent↗
PubMed1994

[Clinical risk factors of vitreoretinal proliferations in rhegmatogenous retinal detachment].

PVR is a complication of rhegmatogenous retinal detachment which can occur only in predisposed eyes. Preoperative PVR and postoperative PVR can develop solely in retinal detachments associated with retinal breaks related to vitreous traction (horse-shoe tears, operculated tears, crescent tears and paravascular tears of the postequatorial region). PVR never develops in retinal detachments due to retinogenic retinal breaks (atrophic holes in lattice, and oral dialysis). There are 3 independent risk factors for postoperative PVR whose role has been demonstrated: preoperative PVR, horse-shoe tears extending on 90 degrees or more of the eye circumference, and horse-shoe tears with a curled and fixed posterior edge. The role of preoperative choroidal detachment as an independent risk factor, although likely, remains to be demonstrated. Cryotreatment is a risk factor for postoperative PVR solely in predisposed eyes. An alternative method to cryo should be used in high risk eyes.

Eye Diseases↗
PubMed1993

[Myopia and rhegmatogenous retinal detachment].

There is a statistically significant correlation between rhegmatogenous retinal detachment and myopia. The prevalence of retinal detachment in myopic eyes is related to the prevalence of the disease precursors in such eyes. In most cases retinal detachments in myopic eyes share the clinical features of retinal detachments in emmetropic eyes. However, retinal detachments associated with giant tears and retinal detachment with atrophic holes in lattice, which are infrequent, show an increased prevalence in the myopic eye. In addition, retinal detachments associated with post-equatorial paravascular retinal tears, as well as retinal detachments with macular holes are specific or the myopic eye. Surgery is required in the management of retinal detachment. At present permanent retinal reattachment can be achieved in approximately 90% of eyes. The indications for prophylactic treatment remain debated. The high incidence of failures of prophylactic treatment is probably related to the limits of the current techniques.

Aging↗