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Biomedical subjects

G Coscas

Publications and source records attributed to G Coscas.

At least 127 records · Page 7Linked to original sources
PubMed1990

Increased red blood cell aggregation in retinal vein occlusion.

Reversible aggregation of red blood cells (RBC) plays an important role in determining the flow properties of blood, and is the cause of the increase in blood viscosity at low shear rates. Retinal venous circulation is characterized by the combination of a low flow state and a high vascular resistance which might severely limit its capacity to adjust to high blood viscosity. These characteristics make the venous circulation in the retina particularly dependent on haemorheological factors. To test the possibility that high RBC aggregation could predispose to the onset and development of retinal vein occlusion (RVO), RBC aggregation and disaggregation (SEFAM erythroaggregameter, France) were measured in 64 patients with RVO. Results were compared to those of a group of 64 controls, similar in age, sex, smoking habit and associated pathologies. Increased RBC aggregation was observed in 52% of the patients, and the mean values showed a highly significant elevation of RBC aggregation parameters in RVO patients (+14%) when compared with controls (P less than 0.001). Subgroups were compared to study the influence of site (central versus branch), form (ischaemic versus non-ischaemic), duration and severity of the occlusion on the aggregation parameters. No significant differences were found between these various subgroups. An increase in RBC aggregability and in the shear resistance of RBC aggregates, by predisposing to circulatory stasis, is likely to contribute to the onset of RVO.

Adult↗
PubMed1990

Binding of basic fibroblast growth factor to normal and neovascularized rabbit cornea.

The labeling pattern of frozen sections of rabbit cornea incubated with radioiodinated basic fibroblast growth factor (bFGF) was investigated in normal corneas and prostaglandin-induced neovascularized corneas by autoradiography followed by image analysis. 125I-bFGF binds to Bowman's, Descemet's, and vascular basement membranes in a dose-dependent manner. The specificity of the binding of bFGF to basement membrane was demonstrated by the following experiments: 1) an excess of unlabeled growth factor displaced the labeling; 2) histones did not modify the labeling; and 3) 2 M NaCl washing and enzymatic treatment with heparitinase prevented binding of labeled growth factor without apparent destruction of the overall structure of the basement membrane. Our results suggest that bFGF binds to the heparan sulfate proteoglycan of basement membranes. Both normal limbal vessels and the newly formed corneal vessels exhibited the same type of labeling but with different intensities, according to the degree of maturation of the new vessels. bFGF binding also is located clearly on the endothelial cells in both types of vessels. This second binding site could correspond to the high affinity receptors on the cell surface and suggests a direct interaction of bFGF with endothelial cells during new vessel formation.

Alprostadil↗
PubMed1990

[Increase of erythrocyte aggregation in retinal vein occlusion].

Erythrocyte aggregation is one of the principal determinants of blood viscosity at low shear rates (low flow). Anatomical and hemodynamical characteristics make retinal venous circulation particularly dependent on hemorheological factors. Erythrocyte aggregation and other laboratory parameters (haematocrit, fibrinogen, plasma proteins, clotting) were measured in 85 patients presenting with retinal vein occlusion and 64 controls matched for age, sex and vascular risk factors (hypertension, diabetes, smoking). Statistical analysis of the results demonstrated a significant difference between the retinal vein occlusion group an the control group for erythrocyte aggregation (p less than 0.001 for the aggregation index at 10 sec and for the threshold of dissociation). The fibrinogen level, haematocrit and plasma proteins (albumin, IgA, IgG, IgM, total proteins, 2-macroglobulin) were similar in the two groups. No statistically significant difference for erythrocyte aggregation was observed between occlusions of the venous branch and occlusions of the central retinal vein or between ischaemic and non-ischaemic forms. These results suggest that raised erythrocyte aggregation mainly explains the increase in blood viscosity previously demonstrated, and could play a role in the constitution of retinal vein occlusion.

Acute Disease↗
PubMed1990

[Macular vitelliform degeneration in adults. Retrospective study of a series of 85 patients].

Since 1974 (Gass), many publications have referred to a macular abnormality that is similar to Best's vitelliform dystrophy, but occurs in adults and shows a normal or subnormal electro-oculogram. In our retrospective study, 85 patients with adult macular vitelliform degeneration were included; 31 patients out of 85 have been followed-up for periods ranging from one to ten years. Women (62,3%) were predominantly affected; the median age was 61 years (ranging from 37 to 81 years); family history did not reveal others affected members except in one case (mother and her son affected); electro-oculogram was recorded in 12 patients and was normal (8 patients) or slightly subnormal (4 patients). During follow-up, vitelliform lesions have shown progressive changes over many years, resulting in a round or oval atrophic area in the central retinal pigment epithelium. Visual acuity was fair at presentation but decreased progressively: at presentation, 43% of the eyes had visual acuity better or equal to 0.6; after 1 year, 59%; after 2 years, 28.5%; after 4 years, 20%, and only 8% of those followed-up for 10 years. Impairment of vision was usually related to alteration of the retinal pigment epithelium and macular atrophy, sometimes to subretinal neovascularization (14 eyes of 12 patients out of 157, or 15% of patients), or rarely to macular edema (2 cases). Several aspects of this disease are still controversial: firstly, the problem whether or not the disease represents a single nosological entity; secondarily its dominant inheritance. The analysis of our cases and of those already published seems to show that the macular changes observed are related to a single disease, well-defined by the epidemiology, the clinical aspects, the natural course. The late onset of the disease, the lack of constant familial involvement and the similarity with other retinal degenerative disorders seem to suggest that vitelliform macular lesions may represent a distinct subgroup of age-related macular degeneration, with a possible genetic predisposition.

Adult↗
PubMed1990

[Scanning laser ophthalmoscopy. Its value in macular diseases].

The scanning laser ophthalmoscope provided a high quality television image of the fundus with minimal illumination of the retina. This new device based on a totally new electro-optical principle allowed a detailed exploration of macular function directly under simultaneous fundus control. The focused beam of a yellow krypton laser (568,2 nm) was swept up and down, rights and links across the fundus to form a raster of parallel lines on the retina. The S.L.O. illuminated only a single retinal point at a time and illumination was reduced to less than 70 microw/cm2 versus 100,000 microns/cm2 for indirect ophthalmoscopy and 4,000,000 microw/cm2 for fluorescein angiography. The intensity of the laser beam could be modified with the microcomputer by means of an acousto-optic modulator. It was possible to produce static or dynamic graphic designs that were simultaneously viewed by the patient and observed by the examiner on the patient's fundus on the video monitor. Further computerized analysis of the videotaped scanning laser ophthalmoscopic images gave a functional retinal map with correction for shifts of stimulus position due to fixational saccadic eye movements. The map showed true retinal location of 1. fixation area; 2. scotoma. The clinical evaluation was completed with 3. measurement of visual acuity in any foveal or parafoveal location. The results of scanning laser ophthalmoscopy were illustrated with the report of datas in a patient with diffuse retinal pigment epithelial decompensation.

Adult↗
PubMed1990

[Dye lasers: experimental histopathologic study of the effects of various wavelengths on the macular region].

Pathological experimental study of dye laser photocoagulation simulating the confluent treatment of subretinal new vessels in the macular area of a Macacas Cynomolgus monkey. 38 days after treatment the lesions become similar on the choriocapillaris and retinal pigment epithelium whatever the wavelength; the choriocapillaris is always occluded and the pigment epithelium destroyed. The internal limiting membrane is ondulated only with yellow and orange colors. These results are compared to those of similar experimental studies.

Animals↗
PubMed1989

[Macular degeneration related to age].

Age related macular degeneration (A.R.M.D.) is the first cause of registered blindness in the developed countries after the age of 50. The prevalence of the disease increases with age. Risk factors have been identified. The atrophic form of age related macular degeneration, the most frequent form, results in a moderate decrease in visual acuity. The neovascular form of A.R.M.D. is associated in natural history with a central scotoma within 2 years. The disease involves both eyes with time. Fluorescein angiography allows an accurate diagnosis in identifying the subretinal new-vessels, and their location. The efficiency of blue green argon photocoagulation has been demonstrated on visual acuity by randomised trials, when the new vessels extend at more than 200 microns from the center. For new-vessels closer to it, monochromatic wavelengths can achieve the destruction of the neovascularization. But, laser photocoagulation is not the treatment of the basic process of A.R.M.D.

Aged↗
PubMed1989

Immunological study of acidic fibroblast growth factor (aFGF) distribution in the eye.

During the last ten years, several groups, including the present authors, have detected growth factor activities in various ocular tissues, and the presence of a ubiquitous Eye-Derived Growth Factor (EDGF) has been described. More recently, isolation and characterization of this growth factor activity from the retina led to the identification of two molecules. These molecules were shown to be identical to other growth factors isolated from neuronal and non-neuronal tissues and are now designated as acidic and basic fibroblast growth factor (aFGF, bFGF). The biological function and the reason for the ubiquitous distribution of these factors remain unclear. Understanding may be improved by quantification of this distribution in various tissues during development. In the present study, specific polyclonal antibodies were raised against acidic FGF, aFGF was determined in various ocular tissues by enzyme immunoassay, and the localization of immunoreactive aFGF by immunohistological staining with fluorescent antibodies or with enzyme- or gold-labeled antibodies was studied. In almost all tissues tested aFGF was found; but the retina, cornea, and vitreous body contained the highest levels of aFGF per gram of tissue. In the retina, aFGF was associated primarily with the nerve fiber layer and the inner and outer segments of the photoreceptors, whereas corneal aFGF was detected in the cytoplasma of the basal layer of epithelial cells.

Animals↗
PubMed1989

[Indications for photocoagulation in idiopathic retinal periphlebitis].

Fourteen patients (23 eyes) with idiopathic retinal periphlebitis were followed during a mean time of six years. Argon laser photocoagulation was performed in 18 eyes: in 11 eyes for large retinal ischemic areas, and in 7 eyes for disc or peripheral neovascularization. Beneficial results were obtained in 72.5% of the treated patients. Laser photocoagulation seems to be useful to prevent or reduce ocular neovascularization associated with idiopathic retinal periphlebitis, and to prevent vitreous hemorrhage. Photocoagulation did not increase ocular inflammation and should be limited to ischemic areas.

Adult↗
PubMed1989

[Practical aspects of the evaluation of preoperative aniseikonia].

Ten years ago, Dr. Simone Delthil, who was one of the first, in France, to make researches into aniseikonia, departed from this life. This anniversary offers the opportunity to the authors to recall that it is most desirable, before operating, that theoretical modifications of the size of retinian pictures should be considered, according to the selected compensatory method, especially in the case of anisometropia or unilateral aphakia.

Aniseikonia↗
PubMed1989

[Vitreous hemorrhage complicating age-related macular degeneration. Apropos of 18 cases].

Vitreous hemorrhage as a complication of Age-Related Macular Degeneration (ARMD) is not a frequent event: 19 cases (out of 18 patients) are reported, corresponding to 0.6% of the patients with ARMD seen in the Department of Ophthalmology of Créteil between January 1st, 1979 and December 31, 1986. The relation between ARMD and vitreous hemorrhage was easy to establish on fundus examination after the resorption of the hemorrhage. However, during the acute hemorrhagic phase, the diagnosis was helped by the other eye fundus examination: this second eye presented with ARMD lesions in 15 out of 18 cases (78.9%). The most challenging differential diagnosis was the choroidal melanoma, when a subretinal hematoma hindered all underlying structures. Vitreous hemorrhages originated generally from well developed subretinal new vessels (17 cases out of 19) arising from the choroid. A retinal pigment epithelium tear, spontaneous or secondary to photocoagulation, was suspected to be the cause of the vitreous hemorrhage in one eye. Finally drugs (3 cases) and systemic diseases (6 cases) seemed to play a role. Visual prognosis is poor in most cases, as the result of the destruction of the macular photoreceptors (six eyes only retained a visual acuity equal or better than 20/400). Laser photocoagulation of the subretinal new vessels was possible for 5 eyes and allowed stabilisation of visual acuity in 2 eyes and improvement in one eye. Vitreous hemorrhage cleared in 16 out of 19 during the follow-up period and vitrectomy was therefore not performed in our series and not indicated at early stages.

Aged↗
PubMed1989

[Collodion baby. Apropos of a case with eye manifestations].

We report a case of a male collodion baby, born at term of a consanguineous couple of Afghan origin. The new-born baby displayed a pseudo-dysmorphic syndrome predominant of the face, with a marked ectropion of the upper and lower eye-lids and chemosis, without corneal involvement. The condition improved with time but complete regression was not obtained. Collodion baby syndrome is a pathologic skin condition observable during the neonatal period. Long term evolution is towards ichthyosis in 90% of cases, and resolution in 10%.

Ectropion↗