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Biomedical subjects

G Renard

Publications and source records attributed to G Renard.

At least 163 records · Page 9Linked to original sources
PubMed1997

[Laser and corneal surgery: pathological anatomy].

The studies of the effects of different lasers on the cornea have usually been done on animals. These studies show that ultra-violet lasers (Excimer 193 nm, 213 nm) have a pure photo-ablative effect, without distant lesions. The corneal endothelium is always intact as long as the laser beam is acting at a distance of more than 50 microns from the cells. The same findings after photo-ablation is the presence of a fibroblastic scar after epithelial healing. This scar correspond to the haze observed in clinical conditions. The infra-red lasers (Intrastomal YAG) produce an important thermal effect the corneal stroma and a destruction of the corneal endothelium if influence and frequency are increased. In conclusion, the lasers used in corneal surgery appear to be safe for the corneal structure but histological studies remain necessary for the new lasers in order to be certain of their safety.

Cornea↗
PubMed1997

[Ring recurrence of ciliary body melanoma after proton-beam therapy].

A malignant ciliary body melanoma was treated by proton-beam irradiation. Ring-shaped recurrence with extraocular extension appeared thirty-six months later and required enucleation. Histologic study revealed a predominant epithelioid cell type tumor, flattened in previously treated area. Proton-beam irradiation efficiency depends on clinical evaluation, which remains questioned in ciliary body locations where circumferential extension could be misevaluated.

Aged↗
PubMed1997

[Differential diagnosis of conjunctival melanoma: exteriorized uveal melanoma].

Four years after unexplained left eye visual loss and 15 days after surgical procedure on the other eye, a 93-year-old female developed a pigmented left conjunctival lesion. Ultrasound examination demonstrated this lesion to be in fact an extraocular extension of uveal melanoma. The patient was treated by external radiotherapy after expanded enucleation.

Aged↗
PubMed1996

Incorporation of a fluorocarbon polymer implanted at the posterior surface of the rabbit cornea.

An implant of porous expanded polytetrafluoroethylene (PTFE) in the corneal stroma allows fast cell colonization and can become translucent. We studied the behavior of the same polymer implanted in the anterior chamber of the rabbit eye and sutured to the posterior surface of the cornea. The expanded tetrafluoroethylene was provided as 200-micron thick sheets in 3 pore diameters (20, 50 and 80 microns). Disks (5 mm) were implanted in the anterior chambers of 20 rabbits and sutured to the posterior surface of the cornea. Histological and ultrastructural studies were performed after 3 and 4 months. Quantimetry was done on TEM images to analyze the fibrillar structure of the intercellular matrix inside and around the implanted polymer. The material was well tolerated. In all cases there was mild central corneal edema, which disappeared after 1 month. Mild neovascularization occurred in five cases, decreasing after 1 month. The polymer became translucent after 8 days. Keratocytes from the corneal stroma colonized the implant via breaks in the Descemet's membrane along the sutures. Quantimetry showed three types of fibrils inside and beside the polymer. Corneal endothelial cells regenerated over the fibroblasts and the polymer. This fluorocarbon polymer implanted in the anterior chamber and sutured to the posterior surface of the cornea was well tolerated, and there was real incorporation, with keratocytes producing collagen fibrils inside the polymer and endothelial cells forming a posterior cell monolayer. This is promising for the development of a keratoprothesis with posterior fixation.

Animals↗
PubMed1996

Collagen synthesized in fluorocarbon polymer implant in the rabbit cornea.

The integration of microporous polymer into tissues is of great interest for the production of keratoprosthetic devices. Our previous studies showed functional differentiated cells and collagen synthesis in the pore of an expanded polytetrafluoroethylene implant. This study identifies and quantifies collagen types synthesized in the implant. Expanded polytetrafluoroethylene polymers were implanted in the rabbit corneas. The collagen extracted from the polymer and implanted stroma after 1, 3 and 6 months was quantified by measuring hydroxyproline. The relative proportions of collagen types were determined by densitometric analysis after SDS-PAGE. The collagen-to-protein ratio in the polymer increased from 0.22 to 0.70 between the first and third month after implantation becoming similar to control cornea. So that of the protein and collagen densities in the polymer and implanted stroma were similar to the control from the third month. The collagen synthesized in the polymer was mainly type I (87%) plus a small amount of type III (8%) 1 month after implantation. The collagen distribution from the third month after implantation was similar to that of the controls and remained constant thereafter in the polymer implant and in the implanted stroma. Immunogold labelling techniques confirmed these results. Implantation of this PTFE disc induced no obvious modification of the corneal stroma, confirming that this polymer is a good interface that is compatible with the native corneal stroma. The keratocytes in this polymer rapidly adopted a corneal phenotype, distinct from the dermal or scaring phenotype as shown by the collagen types produced in the implant.

Animals↗
PubMed1996

[Artificial cornea].

The cornea is the anterior transparent hole of the eye and its replacement by a synthetic material proves indispensable in some kinds of corneal blindness when penetrating keratoplasty is impossible. For a long time, the keratoprosthesis have been developed by different authors but results were always disappointing. Our personal works have been centered on the utilization of an expanded fluorocarbon polymer as interface between the optic of the keratoprosthesis and the cornea of the recipient. This material has given us a lot of satisfactions but our prosthesis did not meet the criteria of a real artificial cornea because the rigid optic induced mechanical tolerance problems and did not allow the measure of the intraocular pressure. We have developed a new model of artificial cornea with a soft optical zone with a diameter of 6 mm and an haptic made of expanded fluorocarbon polymer pretreated in order to induce a fast cellular ingrowth. We hope that this new optical device could improve optical results and tolerance.

Cornea↗
PubMed1996

[Efficacy and tolerability of a combination of indomethacin and gentamicin for preventing inflammation after cataract surgery].

PURPOSE: The aim of the study was to compare 2 combinations of anti-inflammatory drug and antibiotic, in patients undergoing cataract surgery: 0.1% indomethacin/gentamicin or 0.1% dexamethasone/ neomycin. METHODS: Two hundred and two patients undergoing extra-capsular cataract extraction with posterior chamber lens implantation were included in a randomized, double-blinded multicentric study comparing 2 parallel groups of treatment. Treatment was administered the day before surgery, the day of surgery and for the following 7 days. On the 8th post-operative day, the antibiotic was stopped and the anti-inflammatory treatment continued alone until the 30th post-operative day. Post-operative ocular inflammation was assessed clinically on the 1st, 7th, 15th and 30th post-operative days. The main evaluation criterion of treatment efficacy was the assessment of anterior chamber flare and cells. RESULTS: No statistically significant difference-was observed between the 2 treatment groups concerning post-operative inflammation. Both treatments were well tolerated. CONCLUSION: Eye drops combining 0.1% indomethacin and gentamicin proved to be effective and well tolerated in preventing inflammation after cataract surgery.

Adult↗
PubMed1996

[Epinephrine stability in solutions for intra-ocular irrigations].

PURPOSE: Epinephrine may be used for ocular irrigation during ophthalmic surgery when diluted in balanced saline solutions. In aqueous solution, epinephrine breakdown depends on pH, light, temperature, oxidating agents and increases with time. METHODS: The stability of epinephrine in plastic bags prepared in low concentrations (1 mg/L) was studied by HPLC analysis with UV detection, completed with pH determinations, performed after storage (protected from light) in various conditions: at room temperature (+25 degrees C), at +4 degrees C (in a refrigerator), at -20 degrees C (in a freezer). Spontaneous defreezing at room temperature was compared to accelerated thawing in a microwave oven. RESULTS: Epinephrine diluted in ocular irrigation solutions (1 mg/L) was stable for 2 days at room temperature, 14 days at +4 degrees C and 35 days at -20 degrees C. Microwave thawing did not alter the stability of epinephrine. CONCLUSION: The preparation of epinephrine solutions for intra-ocular irrigation may be centralized if the bags are stored less than two weeks in a refrigerator and less than one month in a freezer.

Drug Stability↗
PubMed1995

Keratoprosthesis with biocolonizable microporous fluorocarbon haptic. Preliminary results in a 24-patient study.

BACKGROUND: Most complications of a keratoprosthesis occur at the tissue-to-implant interface. The ideal prosthesis would eliminate this interface by having the tissue actually grow into the supporting material. We present a prospective clinical human study of a novel biocolonizable keratoprosthesis in 24 eyes of 24 patients. DESIGN: To promote implant stability, the 9-mm-diameter haptic was fashioned using a custom-made microporous fluorocarbon with a 4-mm-diameter, 2.67-mm-long, central optic made of medical grade polymethylmethacrylate, giving a global visual field of 110 degrees to 130 degrees. Only bilaterally blind patients with untreatable corneal diseases were included in the study. The haptic was inserted into a lamellar pocket delaminated in the stroma, and the optic was positioned through a hole trephined in the central cornea. RESULTS: The average follow-up was 15.7 months (range, 4 to 28 months). The host corneal fibroblasts penetrated and proliferated into the peripheral microporous fluorocarbon and provided anchorage between the cornea and prosthesis. Seventeen patients (70.8%) had visual acuity improvements. Mean corrected final visual acuity was 20/100 (range, 20/30 to 20/400). Five anatomic failures occurred in the first 6 months (three extrusions, one dislocation of the optic, and one endophthalmitis). We had one case (4.1%) of treatable glaucoma. We successfully removed four of five retroprosthetic membranes that had occurred. No retinal detachment occurred. CONCLUSION: The biocompatible inert microporous polymer did not eliminate all mechanical complications associated with a keratoprosthesis.

Adult↗
PubMed1995

Corneal wound healing modulation using basic fibroblast growth factor after excimer laser photorefractive keratectomy.

Photorefractive keratectomy with the 193-nm excimer laser is one of the most promising innovations in refractive surgery. However, routine clinical application is hindered by two main obstacles, i.e., postoperative subepithelial opacity and possible regression of the refractive result. Because we have previously demonstrated beneficial effects of basic fibroblast growth factor (bFGF) on corneal epithelial healing in different in vivo models, we investigated the influence on both epithelial and stromal healing of topical bFGF after excimer laser keratomileusis in a rabbit model. After 7-mm circular deepithelialization, the eyes of 24 New Zealand White rabbits received identical deep stromal laser ablations (depth 50 microns, 6 D, diameter 5 mm) and were randomly assigned to one of four treatment groups [control (phosphate-buffered saline, PBS), bFGF 10 micrograms/application, dexamethasone 0.1%, bFGF + dexamethasone, n = 12 eyes/group]. All treatments were administered four times daily--bFGF until complete epithelial healing, dexamethasone and PBS until 3 months postsurgery. Wound surface regression on time was determined by means of computer-assisted image analysis of fluorescein-stained corneas. Corneal opacity was observed biomicroscopically and graded using a previously established scoring system. After bFGF application for 2-3 days only, a highly significant acceleration in epithelial wound healing speed was found compared with the rate of the other three treatment groups (p < 0.001). A combined therapy (bFGF + steroid) had no effect on the healing rate. Compared with control values, mean scores for subepithelial haze in the other groups were found to be nearly 50% lower during the first 2 postoperative months.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Comparative prospective study of effects of Biovisc and Healonid on endothelial cell loss and intraocular pressure in cataract surgery].

PURPOSE: The goal of this trial was to evaluate the efficacy (protective action on corneal endothelium and ability to facilitate the procedure) as well as safety (effect on intraocular pressure and inflammation) of Biovisc (new viscoelastic agent made of 1% sodium hyaluronate produced by bacterial fermentation) versus Healonid) postcataract surgery (manual or phacoemulsification). METHODS: 106 patients, 45 males and 61 females (31-94 years) were included in this prospective randomized multicentre trial and followed up for three months. Specular microscopy and intraocular pressure (IOP) measurement were the main evaluation criteria. RESULTS: At D 90, no significant difference was observed between the two viscoelastic agents on the mean endothelial cell loss (group Viovis: -8.6%; group Healonid: -6%) as well as on IOP (early peaks were transitory and resolutive). CONCLUSION: Biovisc and Healonid were similar in terms of efficacy and tolerance.

Adult↗
PubMed1994

Expanded fluorocarbon for keratoprosthesis cellular ingrowth and transparency.

The development of a synthetic material allowing increased cellular adhesion and ingrowth would improve keratoprosthetic devices and requires an understanding of cell colonization processes. Interlamellar implantation of hydrophobic synthetic material may lead to poor corneal nutrition with subsequent necrosis. The probability of necrosis increases with material which is more impermeable, larger in diameter and more anterior in its placement. In this study we demonstrated the importance of pore diameter in the rate and density of cell colonization. We demonstrated that an opaque hydrophobic material may become translucent and wettable with very low perturbation of flow through the cornea. We used an expanded polytetrafluoroethylene with either 20 microns or 50 microns pore diameter. Cellular ingrowth was significantly greater in the material with 50 microns pores, resulting in collagen deposition within the pores without corneal vascularization at 6 months follow-up. Immunohistochemical study with monoclonal antibody AE5 revealed normal epithelial differentiation on the surface of the cornea over the implanted polymer.

Animals↗
PubMed1994

Phase II trial of anaxirone (TGU) in advanced colorectal cancer: an EORTC Early Clinical Trials Group (ECTG) study.

Anaxirone, a rationally synthesised triepoxide derivative, was given to 46 patients with metastatic colorectal cancer. Good risk patients received 800 mg/m2 as a rapid intravenous injection every 4 weeks, whereas poor risk patients received 650 mg/m2. Of 46 patients, 45 were evaluable for toxicity and 42 for efficacy analysis. There were 37/45 patients with poor risk, showing no difference in toxicity as compared to good risk patients. The major toxic effect was myelosuppression with 34% of all patients experiencing grade 3 or 4 leucopenia; thrombocytopenia was less frequent. Locoregional phlebitis occurred in 66% of the patients. There was no objective tumour response to anaxirone in 42 evaluable patients. Only 4 patients achieved stabilisation of the disease lasting maximally up to 248 days. Anaxirone is inactive in metastatic colorectal cancer.

Adult↗
PubMed1994

[Severe keratomycosis. Diagnosis and treatment].

We reported three consecutive cases of severe fungal keratitis initially undiagnosed by corneal scrapping. Corneal biopsy showed fungal elements of Paecilomyces lilacinus, Fusarium solani, Scedosporium apiospermum. Most cases of fungal keratitis could be treated successfully if adequate antifungal therapy were started early. Early and accurate diagnosis is of major importance. The results of our cases confirm the superiority of corneal biopsy over corneal scrapping. Corneal biopsy is a procedure of choice in suspected cases of keratomycosis in which corneal scrapings fail.

Abscess↗
PubMed1994

Basic fibroblast growth factor modulates corneal wound healing after excimer laser keratomileusis in rabbits.

We have previously demonstrated beneficial effects of basic fibroblast growth factor (bFGF) on corneal epithelial healing in different in vivo models. In the present study, we investigated the influence on epithelial and stromal healing of topical bFGF after excimer laser keratomileusis in a rabbit model. The corneas of 24 New Zealand white rabbits were deepithelialized (7-mm diameter) and subsequently received identical deep stromal laser ablations (depth, 50 microns; 6 D; diameter, 5 mm). The animals were randomly assigned to one of four treatment groups: PBS (control); bFGF at 500 ng/application; dexamethasone 0.1%, and bFGF+dexamethasone (n = 12 eyes/group). All treatments were given four times daily; with bFGF being given until complete epithelial healing and dexamethasone and PBS, until 3 months postsurgery. Wound surface regression on time was determined by means of computer-assisted image analysis of fluorescein-stained corneas. Corneal opacity was scored using slit-lamp observation and graded following a previously established scoring system. As compared with the other three treatment groups, a highly significant acceleration in the rate of epithelial wound healing was found after bFGF application for 2-3 days only (P < 0.001). A combined therapy (bFGF+steroid) had no effect on the healing rate. As compared with control values, the peak scores for subepithelial haze were significantly lower in eyes that had received bFGF; the regression on time of the haze in the growth factor group paralleled that in eyes receiving continuous steroid treatment. These results demonstrate for the first time the efficiency of a growth factor in modulating the wound-healing response after excimer laser photoablation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗