Search PubMed⌕ Search

Biomedical subjects

G Renard

Publications and source records attributed to G Renard.

At least 145 records · Page 8Linked to original sources
PubMed1997

Influence of ePTFE polymer implant permeability on the rate and density of corneal extracellular matrix synthesis.

Microporous polymers have great potential for the production of corneal keratoprosthetic devices. Keratocytes invade the pores of expanded polytetrafluoroethylene implants (ePTFE) and collagen synthesis occurs. This ePTFE becomes translucent after its implantation in the stroma of rabbit cornea. The rate and density of cell growth within this polymer depends on the implant thickness, pore size, and its placement in the cornea. We have investigated the influence of the polymer permeability on the collagen and protein contents ePTFE implants. Rabbit corneal stroma were implanted with ePTFE disks (6 mm in diameter) by intralamellar keratoplasty. The implanted polymers were removed from the stroma after 3 to 6 months. The collagen and protein contents were determined after pepsin solubilization. The collagen content of the high-permeability implant was 3.7-fold greater than that of the low-permeability implant 3 months after implantation and 2.4-fold greater after 6 months. The total protein content of the high-permeability implant was 2.5-fold greater than that of low-permeability implant at 3 months and was the same after 6 months. The collagen-to-protein ratio was 68% in the high-permeability implants, and thus similar to that of normal corneal stroma. Thus, high polymer permeability increased both the rate and density of the corneal extracellular matrix ingrowth.

Animals↗
PubMed1997

Corneal hyaluronan content during post-ablation healing: evidence for a transient depth-dependent contralateral effect.

The hyaluronan content during wound healing following excimer laser photoablation was investigated. Rabbit corneas were photoablated (Summit Omnimed, 193 nm, 5 mm diameter, 50 microns and 100 microns depth). Central optical zones of photoablated and contralateral corneas were removed 7, 30 and 90 days after surgery. Corneas from 2 untreated rabbits were used as control. Hyaluronan content was determined after pepsin-solubilization using an alkaline-phosphatase linked hyaluronectin sorbent assay. The hyaluronan content of non-photoablated contralateral corneas was significantly increased and the changes appeared depth dependent. Hyaluronan content returned to control levels by the first month at 50 microns depth and by the third month at 100 microns depth in contralateral corneas. The hyaluronan content of the photoablated corneas was not significantly different from that of the non-photoablated contralateral sample regardless of the depth of photoablation. By contrast, the hyaluronan content of the treated corneas was significantly higher than that of the controls during the first month post-surgery and returned to control values by the third month. Thus the hyaluronan contents in the photoablated and contralateral corneas after excimer laser corneal photoablation were very similar during wound healing. This study shows that excimer laser photoablation induced transient depth-dependent contralateral alterations of the hyaluronan content.

Animals↗
PubMed1997

Endothelial damage caused by uncoated and fluorocarbon-coated poly(methyl methacrylate) intraocular lenses.

PURPOSE: To assess endothelial damage induced by poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) coated with a fluorocarbon polymer, Teflon AF, to make them highly hydrophobic. SETTING: Department of Ophthalmology. Hôtel-Dieu Hospital, Paris, France. METHODS: Ten Teflon-coated and 10 uncoated PMMA IOLs were used in an in vitro static touch model. The corneal endothelium was placed in direct contact with the IOL for 15 seconds and then stained with trypan blue and alizarin red. The endothelial damage produced by each IOL in the area of contact was assessed semiquantitatively and quantitatively. RESULTS: Teflon-coated IOLs produced significantly less endothelial damage than uncoated PMMA IOLs (P < .0001). Endothelial cells in contact with Teflon-coated IOLs did not usually adhere to the IOL surface. In contrast, the uncoated IOLs produced large areas of endothelial cell loss. CONCLUSION: Teflon-coated PMMA IOLs have an antiadhesive effect that reduced endothelial damage after IOL insertion in an in vitro model.

Animals↗
PubMed1997

[Reticulated polyethylene oxide for gel injection adjustable keratoplasty. Biocompatibility in critical situation].

BACKGROUND: GIAK is a surgical technique developed for the correction of myopia. We evaluated the biocompatibility of a gamma-ray crosslinked poly(ethylene oxide) gel in two critical situations. MATERIALS AND METHODS: In 3 rabbits, a 5 mm inner diameter annular channel of 1 mm width was delaminated at 80% corneal depth and a sterile gamma-ray crosslinked polyethylene oxide gel was injected in the channel. In cornea 1 (control), the annulus was centered on the corneal apex and the channel was fully filled with gel. In cornea 2, the delamination was purposely decentered and the channel was approximately 1 mm from the limbus at its closest point. In cornea 3, the centered channel was purposely partially filled. After a 6 month follow-up, the rabbits were sacrificed for histology. RESULTS: Histopathology showed the oval channel walls to be irregular and a slight thinning of the epithelium located above the implant but no abnormalities in the stromal thickness. No mononuclear, polynuclear cells or other signs of encapsulation or rejection were found around the polymer in any of the animals. In cornea 3, fibroblasts were found on the lateral sides of the hydrogel globules. No limbal neovascularization was observed over the 6 month period in any of the animals. CONCLUSIONS: The injected PEO gel followed intimately the delaminated stromal channel and was well tolerated in the cornea. The fibroblastic reaction found in partially filled channels is caused by the normal wound healing process and not by the hydrogel chemical properties.

Animals↗
PubMed1997

[2nd generation bio-integrated keratoprosthesis. Implantation in animals].

PURPOSE: Our goal was to evaluate a second generation biointegrable keratoprosthetic device (BioKpro II). METHODS: The device consists of a porous transparent PTFE (12 mm diameter) and a soft copolymer structure for the optical system (7 mm diameter). Intraocular pression was evaluated with a Goldmann tonometer on an artificial chamber. A lamellar dissection was carried out 3 mm radially for 360 degrees creating a pocket to accommodate the skirt. The soft optic (42.5 D; 500 microns thick) was positioned through a hole (6 mm in diameter) trephined in the central cornea. A 360 degrees peritomy was performed and conjunctiva was placed in front of the prosthesis, sutured and was opened 15 days post implantation. 14 rabbits were implanted and were allowed to heal for three months. RESULTS: We are able to measure the intraocular pressure by Goldmann tonometer on an artificial chamber. We did not observed epithelialisation on the hydrophilic optical surface (14/14). Aseptic necrosis in direct contact between cornea and the soft optical system was observed when conjunctiva was not effective (4/14). As observed with the first generation devices, conjunctiva or buccal mucosa is needed to avoid local necrosis. In other cases no adverse reactions were observed after implantation. DISCUSSION: The geometry and biomechanical properties of the BioKpro II is closed to that of the human cornea. The junction between the optical and the flange was bound by polymeric interpenetration and prosthesis dislocation was not seen under pressure over 1000 mmHg. CONCLUSION: Second generation biointegrable keratoprostheses (BioKpro II) can be implanted successfully. Further tests will determine if surface modifications designed to promote epithelial cell attachment on the optical system could prevent ulceration at the junction between the fluorocarbon and the core.

Animals↗
PubMed1997

[The optical power of the corneal epithelium. In vivo evaluation].

PURPOSE: The refracting power of the corneal epithelium is relatively unknown. We measured the keratometric refracting power of the cornea on 15 eyes of patients undergoing photorefractive keratectomy with and without epithelium. MATERIALS: The readings were performed with a videokeratoscope TMS-1. Three readings were averaged to obtain the mean and standard deviations. RESULTS: By removing the epithelium, there was an increase in corneal refracting power. The mean change was +1.19 D (standard deviation +/- 0.36 D) at 1 mm of the center of the cornea. On all patients the optical power of the cornea increased after epithelium removal. CONCLUSION: The curvature of the Bowman membrane is steeper than the cornea with epithelium. A change in the thickness of the epithelium is related to a modification of the optical power of the cornea. The optical role of the epithelium is to compensate surface irregularities of the Bowman membrane and could explained in part the hyperopia in the first months after excimer laser.

Cornea↗
PubMed1997

[Quantitative topographic detection of keratoconus in the contralateral eye in clinically unilateral keratoconus. Apropos of 5 cases].

BACKGROUND: Keratoconus is generally bilateral and follows an asymmetrical course. The goal of this study was to evaluate efficiency of the automated topographic screening indices on early keratoconus by examination of the fellow eyes of clinically unilateral keratoconus. PATIENTS AND METHOD: We examined the fellow eyes of 5 cases of clinically unilateral keratoconus by videokeratography using TMS-1 Computed Anatomy device, which incorporates the keratoconus screening indices from Rabinowitz (K and I-S values) and Klyce/Maeda (KPI value and other quantitative induces as OSI, DSI and CSI). RESULTS: One case (number 1) had keratoconus detected by both Rabinowitz and Klyce/Maeda indices. Two cases (number 2 and 3) had normal keratoconus screening indices. Two cases (number 4 and 5) had keratoconus detected by Rabinowitz I-S value, with a 0% KPI value. CONCLUSIONS: Rabinowitz indices are sensitive with a poor specificity. The Klyce/Maeda indices are less sensitive but more specific. Both methods may be useful for keratoconus detection. The results must always be analysed in relation to a clinical observation of both eyes and the course of the topographic changes.

Adult↗
PubMed1997

[Meibomian adenocarcinoma in its blepharo-conjunctival form. Apropos of a case].

A case of Meibomian carcinoma of the left eyelid was observed in a 53-year-old-female patient. SHe had been previously treated for chronic unilateral blepharoconjunctivitis; an excisional biopsy disclosed a Meibomian carcinoma. First a total resection of both left eyelids was performed with plastic reconstructive surgery, three months later a recurrence required an orbital exenteration. This case underlines the interest of an early diagnosis which allows a more conservative treatment. The diagnosis must be kept in mind in any case of chronic unilateral blepharoconjunctivitis; histopathology has a key role in the diagnosis of Meibomian carcinoma.

Adenocarcinoma↗
PubMed1997

[Computerized video-keratoscopic analysis and cataract surgery by phacoemulsification. Predictive calculation of the power of the intraocular implant].

PURPOSE: The authors present the results of a prospective study of 125 consecutive cases of phacoemulsification, performed by a single surgeon, to assess the benefit of computerised videokeratoscopy for the improvement of the predictive calculation of the power of intraocular lenses (IOL). METHODS: Preoperative keratometry was determined by means of 3 concurrent techniques, including automated kerato-refractometry (AKR 2000, Nidek) and videokeratoscopy by TMS-1 (Tomey) and CAS-1 (EyeSys). The results of the IOL calculation by these 3 methods was compared postoperatively to the power of the actual IOL yielding emmetropia as calculated by the optical method based on the postop, refraction at the various time-points. RESULTS: Simulated values obtained with videokeratoscopy significantly reduced the refractive error at 1 postop, week (p = 0.001), one month (p = 0.002) and 3 months (p = 0.002) for the CAS1 and at 3 months (p = 0.002) for the TMS1, as compared to values obtained with conventional automated keratometry. The refractive error was significantly reduced with the CAS1 at one month (p = 0.001) and 3 months (p = 0.019) as compared to TMS1. CONCLUSION: The determination of the anterior curvature of the entrance pupil by videokeratoscopy significantly improves the predictive calculation of the IOL power.

Aged↗
PubMed1997

[Rigid endoscope with Gradient-index lenses. Preliminary studies].

PURPOSE: Endoscopes for use in ophthalmology can be manufactured in dimensions smaller than 0.89 mm. MATERIALS: Gradient-index lenses that give a higher resolution than fiber bundles can be miniaturized down to 0.35 mm. RESULTS: We used this new endoscope in 6 eyes of 6 patients during anterior segment surgery. Preliminary clinical experience has demonstrated the usefulness and practical application of this new instrument. CONCLUSION: The clear views the instrument provides of the ciliary sulcus and ciliary body behind the iris make it useful in secondary posterior chamber intraocular lens implantation, retroprosthetic membrane behind keratoprosthesis, Molteno valve, and in endolaser photocoagulation.

Aged↗
PubMed1997

[A new material for intraocular implant].

PURPOSE: The aim of our study was to evaluate a new fluorocarbon (Teflon AF), used as a coating of poly-methylmethacrylate intraocular lenses. Teflon AF can be dissolved in special solvents (liquid fluorocarbons). It is the first amorphous and transparent form of teflon. MATERIALS AND METHODS: The coating was performed and the surface quality of the teflon-coated lenses was evaluated by scanning electron microscopy. Twenty teflon-coated and 10 uncoated lenses were implanted in rabbit eyes after phacoemulsification. They were compared concerning the presence of iris-lens synechias and the number of deposits on the lens' surfaces. An in vitro static touch model was used to compare endothelial damage produced by the 2 kinds of intraocular lenses. The results from this model were quantitatively analyzed, using the BIOCOM 200 image-processing system. RESULTS: The teflon group had no iris-lens synechias and the control group had 2 extensive synechias. There were significantly fewer deposits on the surfaces of teflon-coated lenses on days 30 and 60 post-operatively (P < 0.0001) than on the control lenses. Teflon-coated lenses produced significantly less endothelial damage than did control lenses (P < 0.0001). CONCLUSIONS: Teflon AF presents an anti-adhesive effect that increases the biocompatibility of polymethylmethacrylate lenses and reduces endothelial damage during their intraocular insertion.

Animals↗
PubMed1997

[Orbital schwannoma. Apropos of a case].

The orbital schwannoma or neurilemoma is a rare tumor. We report herein the single case of a 51-year-old woman presenting an inferior extraconal orbital schwannoma and multiple sclerosis. Surgical treatment with complete excision allowed healing.

Blepharoptosis↗
PubMed1997

[Uncommon corneal hydrops. Apropos of a case].

We report a case of corneal hydrops in a young patient with unremarkable ophthalmologic history or intercurrent identified pathology. Different etiologies of corneal hydrops are discussed.

Adult↗
PubMed1997

[Confocal microscopy study of 2 cases of Thygeson's epithelial keratitis].

Two cases of bilateral Thygeson's keratitis were examined by in vivo confocal microscopy. In the corneas, fine deposits of highly reflected material appeared immediately below the basal lamina. This is the first time that such morphological features are described in patients with Thygeson's keratitis.

Adolescent↗
PubMed1997

[Mooren's ulcer following combined extracapsular crystalline lens extraction and trabeculectomy].

We report the case of a 70-year-old patient who presented with Mooren's ulcer in her right eye following extracapsular cataract extraction combined with trabeculectomy. She was successfully treated by a sclerocorneal graft combined with a large conjunctival resection. Clinical and histological features, and therapeutic outcomes are discussed and compared to previously published data.

Aged↗