PubMed Health⌕ Search

Biomedical subjects

A Mermoud

Publications and source records attributed to A Mermoud.

At least 37 records · Page 2Linked to original sources
PubMed2001

Ageing of Schlemm's canal in nonglaucomatous subjects.

AIM: to study age-related Schlemm's canal endothelial changes and evaluate consequences on the filtration function. MATERIAL AND METHODS: the inner wall endothelium of Schlemm's canal was examined in 9 non-glaucomatous subjects aged between 32 and 75 years, by a combined technique of light and electron microscopy (scanning and transmission). Quantitative analysis included counts of bulges, pores, nuclei, giant vacuoles and other protruding structures, as well as measures of pores, giant vacuoles and Schlemm's canal size parameters (diameter and inner wall width). Outflow facility calculations were realised using a modified previously described mathematical model. RESULTS: The main structures affected by ageing in Schlemm's canal appeared to be giant vacuoles. Their density but also their size is significantly reduced with increasing age. The intracellular pore population is also found to diminish with age and is correlated to that of giant vacuoles, suggesting that those pores are luminal openings of vacuoles. Outflow facility calculations revealed a global decrease of endothelial outflow facility of about 60% between the 3rd and 7th decades. The study also showed a different age-related pattern for the two subtypes of endothelial pores. CONCLUSIONS: Our study demonstrated that Schlemm's canal filtration function is significantly influenced by age, as the endothelial inner wall outflow facility is found to be widely reduced. This is partly the result of an age-related reduction in counts of giant vacuoles and intracellular pores. The second pore population (border or intercellular) doesn't follow the same evolution, but may have a more significant regulator role in transendothelial permeability.

Adult↗
PubMed2001

New Tonopen XL: comparison with the Goldmann tonometer.

PURPOSE: To compare the intraocular pressure (IOP) values obtained using a Goldmann tonometer (Haag-Streit) with those obtained with the new Tonopen XL (Mentor), which has certain differences compared with first- and second-generation models. METHODS: The IOPs of 104 patients were assessed by Goldmann tonometer and Tonopen XL tonometer. Goldmann measurements was done first in 145 eyes and Tonopen measurements were done first in 53 eyes. Four observers measured the IOP. Observers A, B and C used the Goldmann tonometer first and then the Tonopen XL, while observer D used the Tonopen XL first and then the Goldmann tonometer. The results were analysed by descriptive analysis and, when the distribution of the data was normal, paired t-test and Pearson's r coefficient were used to compare and correlate IOP measurements between Goldmann and Tonopen measurements. When the distribution of the data was non-normal, the Wilcoxon matched-pair test and Spearman coefficient were used. The agreement between Goldmann and Tonopen values was also calculated. ANOVA test was used to compare the difference obtained by 'Goldmann minus Tonopen' measurements among the three different observers. RESULTS: A statistically significant difference (p < 0.0001) was found between the IOP readings obtained by Goldmann tonometer and the Tonopen XL and a significant correlation was found between the Goldmann values and Tonopen XL values (p < 0.001). When the Goldmann IOP was more than 20 mmHg the Tonopen XL measurements were lower than the Goldmann values. Also in this group this difference was statistically significant. No significant difference was found between Goldmann values and Tonopen values among the three observers, even though a significant difference was found between Goldmann values and Tonopen values for observer B. When the values obtained by first the Goldmann tonometer and then the Tonopen XL were compared with those obtained by first the Tonopen XL and then the Goldmann tonometer, no significant difference was found between the two groups. CONCLUSION: The new Tonopen XL provides similar results to the Goldmann tomometer in 62% of the cases and was slightly less accurate than the Goldmann tonometer for extreme values, just like the previous Tonopen. Nevertheless the precision is good enough for the purpose of adequate screening.

Analysis of Variance↗
PubMed2001

[Analysis of filtration according to implant type after deep sclerectomy in the rabbit].

PURPOSE: The purpose of this study was to compare the aqueous humor outflow using three type of implants after deep sclerectomy. A numeric imaging system with ICG and fluorescein angiography was used. The evolution over time was recorded, while filtration and outflow facility were measured. MATERIAL AND METHODS: Numeric imaging system with ICG and fluorescein angiography were performed before and after deep sclerectomy at regular intervals after surgery. Both resorbable (collagen) and non-resorbable (hema) intrascleral devices have been tested in eight rabbits. The resorption time of the collagen implants has been monitored using UBM technique. The outflow facility was measured with the technique of anterior chamber canulation and constant pressure method. RESULTS: The resorbable collagen implants could be observed with UBM and angiography during the first six weeks post-operatively. The image of the non-resorbable Hema implant remained clearly visible over time. New drainage vessels were observed around the filtering bleb. The filtration significantly increased as the outflow facility improved after surgery, while the intraocular pressure remained stable over time. CONCLUSION: This conjunction of UBM, angiography and outflow measurement allowed us to study and compare three types of implants used as space maintainer after deep sclerectomy, and analyse their effect on the aqueous filtration and outflow facility.

Animals↗
PubMed2001

MYOC mutation frequency in primary open-angle glaucoma patients from Western Switzerland.

PURPOSE: To determine MYOC gene mutation frequency in patients with primary open-angle glaucoma (POAG) from Western Switzerland. METHODS: A total of 117 unselected index patients with primary open-angle glaucoma were submitted to a full eye examination. DNA was extracted from blood and PCR amplicons of MYOC exon 3 were screened for mutations by single-strand conformation polymorphism (SSCP) analysis. Abnormal conformers were analyzed both by direct bidirectional sequencing and by enzymatic mutation detection (EMD) assay. RESULTS: Ten occurrences of four different sequence changes were detected, including: 1) five times the same disease-causing mutation (Q368X) in five unrelated POAG patients and 2) three distinct polymorphisms in five patients. The patients carrying an MYOC mutant allele were characterized by a broad clinical variability in terms of age of onset (34-77 years) and highest intraocular pressure (IOP) values (23-47 mmHg). CONCLUSIONS: A pathogenic MYOC mutation (Q368X) was identified in 4.27% (5/117) of the studied population from Western Switzerland, which corresponds to the highest frequency yet reported for this mutation.

Adult↗
PubMed2001

Retinal nerve fiber layer and physiological central corneal thickness.

PURPOSE: To determine the relationship between central corneal thickness and the measurement of retinal nerve fiber layer thickness around the optic nerve head using a confocal scanning laser polarimeter such as the Nerve Fiber Analyzer (GDx). METHODS: Forty-four eyes were recruited for this study. Each patient had a normal visual field and a healthy optic nerve head, which was assessed by slit-lamp biomicroscopy with a 90-diopter lens and by a scanning laser ophthalmoscope (Heidelberg Retina Tomograph). Using the GDx, retinal nerve fiber layer thickness was calculated from 1.75 disc diameters together with some standard GDx parameters, including the number, symmetry, superior ratio, inferior ratio, maximum modulation, and ellipse modulation. Corneal thickness was measured with the DGH-1000 ultrasonic pachymeter. Descriptive analysis was used and Pearson's r coefficient of correlation was calculated. RESULTS: Corneal thickness was not significantly correlated to retinal nerve fiber layer thickness, but it was significantly (P < 0.05) correlated to the other GDx parameters. CONCLUSION: From these data. peripapillary retinal nerve fiber layer thickness is shown not to be significantly correlated to the corneal thickness, even if for the standard GDx parameters a significant correlation was found.

Aged↗
PubMed2001

Normal retinal nerve fiber layer thickness in the peripapillary region measured by scanning laser polarimetry.

PURPOSE: To measure retinal nerve fiber layer thickness (RNFLT) as a function of distance from the optic nerve head using a confocal scanning laser polarimeter, such as the Nerve Fiber Analyzer (GDx). METHODS: Twenty eyes of 20 healthy patients were recruited for this study. Each patient had a normal visual field and a healthy optic nerve head, which was assessed by slit-lamp biomicroscopy using a 90-diopter lens and by a scanning laser ophthalmoscope. Using the GDx, RNFLT was calculated from 1.1 disc diameters (DD) to 2.5 DD in 0.1-DD increments from the outer edge of the optic disc rim. RNFLT was successively evaluated for the entire annulus surface, for each quadrant, and for every 10 degree sector. RNFLT was calculated in retardation degrees. Differences in RNFLT were calculated by analysis of variance. RESULTS: When the entire RNFLT was considered, the measurements close to the optic nerve head (at 1.1 and 1.2 DD) were found to be significantly (0.05 < or = P < or = 0.01) different from those measured far from the disc (at 2.4 and 2.5 DD). The inferior quadrant had the greatest RNFLT followed by the superior quadrant. When RNFLT was analyzed for every 10 degrees, RNFLT at 1.1 and 1.2 DD was significantly (P < or = 0.001) different from that measured at 2.4 and 2.5 DD in almost all 36 sectors. In the 36 considered sectors, no significant difference was found for all the RNFLT values that were calculated in all the positions of the annulus surface between 1.1 and 1.7 DD. CONCLUSION: From these data, peripapillary RNFLT is shown to be significantly (P < or = 0.001) thinner in the periphery (2.5 DD) than around the optic disc (1.1 DD). However, the lack of any difference in RNFLT from 1.1 to 1.7 DD suggested that the mild variations to locate the optic disc contour line do not change the results of the analysis if the RNFLT is calculated within 1.8 DD.

Aged↗
PubMed2000

Frequency doubling technique in patients with ocular hypertension and glaucoma: correlation with octopus perimeter indices.

PURPOSE: To ascertain whether frequency doubling technique (FDT) (Welch-Allyn, Skaneateles, NY; Zeiss-Humphrey, San Leandro, CA) indices provide results comparable with those of standard Octopus threshold perimeters (Interzeag AG, CH-8952 Schlieren, CH) in patients with glaucoma and in patients suspected of having ocular hypertension, glaucoma, or both. DESIGN: A comparative, consecutive, case series. PARTICIPANTS: Thirty-nine glaucomatous patients and 41 patients with ocular hypertension or suspected glaucoma were recruited consecutively. METHODS: The visual field of the study participants were assessed by FDT program C-20 full threshold and Octopus program dG1X. Only one eye of each participant was selected randomly. Pearson's r correlation coefficient was calculated among the FDT and Octopus indices. MAIN OUTCOME MEASURES: Using Octopus perimeter, mean defect (MD), mean sensitivity (MS), loss variance (LV), and corrected loss variance (CLV) were calculated and used for correlation. For the FDT, mean deviation (FDT-MD) and pattern standard deviation (FDT-PSD) were calculated and used for correlation. Also, the time required to perform the visual field test was considered. RESULTS: In the entire population, a statistically significant correlation (Pearson's r, P<0.001) was found between FDT-MD and both MS (0.77) and MD (-0.80) and between FDT-PSD and both LV (0.50) and CLV (0.45). When the glaucoma group was considered alone, similar significant correlation was found between the indices. In the suspected ocular hypertension and glaucoma suspect group, no significant correlation was found. A significant (P<0.001) difference was found between FDT and Octopus for the time needed to perform the visual field test. CONCLUSIONS: This new technique could be used both to screen populations and to observe glaucomatous visual field progression in early and moderate stages. The FDT is a faster way to analyze the visual field and captures threshold values for each point, but it is important to remember that this is a new technique and its limits are still unknown.

Aged↗
PubMed2000

Sinusotomy and deep sclerectomy.

Non-penetrating filtering surgery (NPFS) started in 1962 with the first sinusotomy performed by Kraznov. At that time, the author of this new technique believed that the outflow resistance in the majority of cases of primary open-angle glaucoma was located at the level of scleral aqueous drainage veins and not in the trabeculum. He therefore developed a safe NPFS technique, leaving in place the trabeculum and the inner wall of Schlemm's canal. Because of difficulties with the microsurgical technique and the small reduction in intraocular pressure (IOP) compared with trabeculectomy, sinusotomy was abandoned. In the last decade, with the widespread use of operating microscopes, NPFS has been the subject of renewed interest. IOP reduction with the new NPFS techniques is comparable to that obtained with trabeculectomy, with significantly lower pre- and post-operative complications. The new NPFS techniques such as deep sclerectomy, ab externo trabeculectomy and viscocanalostomy present definitively different mechanisms of filtration compared with early sinusotomy. This article will review the history of NPFS as well as describing the different new non-penetrating filtering surgeries.

Filtering Surgery↗
PubMed2000

[Intraocular hypotony: use of ultrasound biomicroscopy (UBM) for differential diagnosis and its schematic representation].

OBJECTIVES: To determine the use of high-frequency ultrasound biomicroscopy (UBM) in the assessment of hypotony and in particular to determine the proportion of cases for which UBM contributed significant additional hitherto unaccessible information. PATIENTS AND METHODS: Ultrasound biomicroscopy was performed in a standard manner, using a Humphrey UBM 840 system (Humphrey Instruments, Inc., San Leandro, CA). UBM findings were analysed and the clinical relevance of UBM information was determined for the whole collective. RESULTS: Twelve patients with hypotony were examined. UBM findings contributed essential information that allowed to reach a diagnosis or that determined the therapeutic attitude in 10 of the 12 hypotonic patients. In two cases the cause of hypotony was tractional ciliary body detachment, in 5 cases it was post-inflammatory atrophy of the ciliary body, in 3 cases it was post-traumatic irido and cyclodialysis, in one case it was supraciliary and suprachoroidal effusion and in the last case it was due to uveal effusion syndrome. Based on these findings we established a schematic approach for hypotony. CONCLUSIONS: This procedure enabled us to assess the morphological changes found in patients with hypotony. In a majority of cases UBM was useful either to orient therapeutic intervention or to establish a diagnosis. On the base of our findings a schematic approach for hypotony, using UBM, was established.

Algorithms↗
PubMed2000

[Aqueous outflow pathway imaging in the rabbit with fluorescein and indocyanine green].

PURPOSE: The purpose of this study was to visualise the rabbit aqueous outflow pathway using a numeric imaging system with ICG and fluorescein injection in the anterior chamber. MATERIAL AND METHODS: We performed a simultaneous injection of Indocyanin Green (ICG) and Fluorescein into the anterior chamber of rabbit eyes. Using a digital camera, we took several sequenced pictures to visualize the distribution of the dyes within the outflow pathway. We observed the dynamics of the outflow over time. RESULTS: In the early phases, the shape of the outflow canal around the limbus was clearly seen. Several collecting veins close to the recti muscles were also identified. There was only slight fluorescein leakage during the early phases, allowing adequate visualization of the morphology of the outflow system. In the late phases, the sclera was stained with the fluorescein, and no details were thus visible. The ICG dye allowed better recognition of the fine details of the outflow structure. CONCLUSION: This method was relatively simple, safe and precise, and allowed us to visualise the details of the outflow pathways in the rabbit eyes. These results could be of great value in further evaluating the outcome of filtering surgeries in animal models.

Angiography↗
PubMed2000

Nonpenetrating filtering surgery in glaucoma.

Since 1967, trabeculectomy has been the standard drainage operation for most cases of medically uncontrolled glaucoma. It is associated with significant risk of hypotony, hyphema, choroidal effusion or hemorrhage, and bleb failure. Toward the goal of a safer and more reproducible glaucoma filtering surgery, nonperforating filtering surgeries are now performed in primary open-angle glaucoma, normal-pressure glaucoma, and most cases of secondary glaucoma. The site of highest resistance to outflow, the juxtacanalicular trabecular meshwork, is bypassed with avoidance of penetration into the anterior chamber. Different techniques of nonpenetrating filtering surgeries are discussed here.

Anterior Chamber↗
PubMed1999

Corneal thickness in ocular hypertension, primary open-angle glaucoma, and normal tension glaucoma.

OBJECTIVES: To determine the effect of central corneal thickness (CCT) on the measurement of intraocular pressure (IOP) and on the resultant reclassification of patients as having primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), or ocular hypertension (OHT). METHODS: Intraocular pressure (Goldmann applanation tonomety) and CCT (ultrasound pachymetry) were measured in 22 patients with NTG, 49 with POAG, 44 with OHT and in 18 control subjects. The CCT was used to obtain a corrected value for the IOP and to reclassify the type of glaucoma. RESULTS: There was no significant difference in CCT between controls (552 +/- 35 microns) and patients with POAG (543 +/- 35 microns), but the CCT in the group with NTG (521 +/- 31 microns) was significantly lower than that in the control group or the group with POAG (P < .001), and the CCT in the group with OHT (583 +/- 34 microns) was significantly higher than in controls or patients with POAG (P < .001). Correcting IOP for corneal thickness, 31% of the patients with NTG could be reclassified as having POAG, and 56% of the patients with OHT as normal. CONCLUSIONS: Patients with NTG have a thinner CCT than do patients with POAG or controls. Underestimation of the IOP in patients with POAG who have thin corneas may lead to a misdiagnosis of NTG, while overestimation of the IOP in normal subjects who have thick corneas may lead to a misdiagnosis of OHT.

Aged↗
PubMed1999

Transport of rimsulfuron and its metabolites in soil columns

This paper presents a study on degradation, sorption and transport of the sulfonylurea herbicide rimsulfuron and its major metabolites in alluvial soil columns. The formulation of rimsulfuron was found to strongly affect its degradability. Hydrolysis of pure rimsulfuron takes place rapidly in distilled water (t(1/2)=2.2 days) or indeed instantaneously in alkaline solution. The formulated rimsulfuron (Titus, 25% rimsulfuron, Du Pont De Nemours) is more persistent in alluvial soil suspensions (t(1/2)=7.5 days). The study of sorption of Titus and its two major metabolites (1 and 2) revealed that these three chemicals are potentially highly mobile in the studied soil: in suspension distribution coefficients of 0.0028, 0.125 and 0.149 cm3 g(-1) were obtained respectively. Given the instability of rimsulfuron in alkaline solutions, the pH effect was evaluated with metabolite 2 in water saturated Fontainebleau sand columns at pH 6, 8 and 10. Transport was found to be strongly dependent on pH; a linear relationship was obtained between pH and the retardation factor or the dispersion coefficient. In alluvial soil columns, rimsulfuron from Titus was found to be very mobile (R=1.2) and rapidly degraded into metabolites 1 and 2, which were transported at a similar velocity. Nevertheless, the risks of groundwater contamination by rimsulfuron seem very low, as it is rapidly degraded under dynamic conditions (t(1,2)=1.4 days). On the other hand the relatively stable metabolite 2 seems likely to persist in the soil and to be transported to the groundwater. Special attention should thus be given to this compound at least as long as its harmlessness is not demonstrated.

Journal Article↗
PubMed1999

Comparison of deep sclerectomy with collagen implant and trabeculectomy in open-angle glaucoma.

PURPOSE: To assess the efficacy and postoperative complications of deep sclerectomy with collagen implant (DSCI), a nonpenetrating filtration procedure. SETTING: Glaucoma Unit, Department of Ophthalmology, University of Lausanne, Switzerland. METHODS: Forty-four eyes of 44 patients with medically uncontrolled open-angle glaucoma had DSCI and a matched control group of 44 patients, trabeculectomy. A superficial scleral flap was raised and a deep sclerectomy performed in the scleral bed. Schlemm's canal was opened, and the cornea was dissected to Descemet's membrane. At that stage, aqueous filtered through the remaining trabeculo-Descemet's membrane. A collagen implant was sutured radially in the scleral bed; the scleral flap and conjunctiva were then closed. Examinations were performed before surgery and postoperatively at 1 and 7 days and 1, 2, 3, 6, 9, 12, 15, 18, and 24 months. RESULTS: The mean follow-up was 14.4 months +/- 6.3 (SD) (range 3 to 24 months). The mean preoperative intraoperative pressure (IOP) was 26.7 +/- 7.3 mm Hg. The mean postoperative IOP was 6.1 +/- 4.5 mm Hg at 1 day and 11.0 +/- 4.4 mm Hg at 1 week; it remained stable for the next 24 months. The success rate, defined as an IOP lower than 21.0 mm Hg without medication, was 69% in the DSCI group and 57% in the trabeculectomy group at 24 months postoperatively (P = .047). The number of postoperative complications was significantly lower in the DSCI group than in the trabeculectomy group. CONCLUSIONS: The success rate of DSCI may be comparable to that of trabeculectomy, with fewer complications.

Aged↗