Magnetic resonance imaging measurements evidence weak dispersion in homogeneous porous media.

We measure the dispersion coefficient through homogeneous bead or sand packings at different flow rates from direct magnetic resonance imaging (MRI) visualizations of the transport characteristics of a pulse of paramagnetic nanoparticles. Through two-dimensional imaging we observe homogeneous dispersion inside the sample, but we show that entrance effects may induce significant radial heterogeneities, which would affect the interpretation of the breakthrough curve. Another MRI approach then provides quantitative measurements of the evolution in time of the longitudinal particle distribution in the sample. These data can be analyzed to deduce the coefficient of dispersion independently of entrance effects. The values obtained for this "effective" dispersion coefficient are almost ten times lower than the commonly accepted values.

[Long term follow-up of bleb reconstruction after glaucoma filtering surgery]. / Réfection de bulle de filtration après chirurgie du glaucome. Résultats tonométriques à moyen terme.

PURPOSE: To study the long term outcomes of surgical bleb reconstruction after glaucoma filtering surgery. METHOD: A retrospective study of 46 eyes (43 patients, mean age 67.9 years +/-12.2, 30 women, 13 men) that underwent surgical bleb reconstruction for leaking bleb (56.53%), major bleb dysesthesia (17.39%), or extend bleb over cornea (26.08%). Bleb resection associated with the covering of filtering surgery site with conjunctival flap was performed 38.5 months (+/- 45.2) after initial filtering surgery. RESULTS: After a follow up of 24.3 months (+/- 17.9), intra ocular pressure was increased in 85.2% eyes: +3.56 mmHg (+/- 4.3, p<0,001), and a new hypotonic medication was needed in 26 %. Bleb dysesthesia was reduced in any case and none of the bleb was leaking any more. CONCLUSION: Bleb excision with conjunctival advancement is a safe and effective procedure for the treatment of late bleb leak or major bleb dysesthesia. However in most cases, intra ocular pressure increase after reconstruction and new hypotensive medication may be required.

[Clinical factors favoring excessive subconjunctival fibroblastic proliferation after glaucoma surgery]. / Facteurs cliniques favorisant la cicatrisation conjonctivale excessive après chirurgie du glaucome.

PURPOSE: To understand risk factors for failure of glaucoma filtering surgery. PATIENTS: A retrospective study of 67 eyes (16 nonpenetrating trabeculectomies, 51 trabeculectomies [31 with 5FU and 20 with mitomycin]) of 61 patients in whom 5FU bleb revision was needed because of increasing intraocular pressure. Postoperative incidents were analyzed to explain excessive subconjunctival fibroblastic proliferation. RESULTS: In eight cases, IOP increased after 6.16 months (+/-2) and for 59 eyes, after 33.5 days after surgery (+/-11.4). Postoperative incidents were 24 (35.9%) bleb leaks, nine cases (13.4%) of hypotony with choroidal detachment, six (9.0%) iris incarcerations, seven (10.4%) cystic blebs, and 21 (31.3%) inflammatory flat blebs. After a mean follow-up of 27 months +/- 18, the success of bleb 5FU revision was 84.6% for nonpenetrating trabeculectomy (without glaucoma treatment, 69.2%; with medical treatment, 15.4%) and 73.9% for trabeculectomy (47.8% and 32.6%). CONCLUSION: Postoperative outcomes favor an inner or outer obstacle to conjunctival filtration. Aqueous humor can no longer remain in the subconjunctival spaces, increasing the risk of glaucoma surgery failure. Early follow-up of glaucoma surgery is crucial to obtaining long-lasting filtration.

[What should we think? Is pneumotonometry still reliable?]. / Que faut-il en penser? La tonométrie à air est-elle encore fiable?

UNLABELLED: Noncontact tonometer (NCT) is an applanation tonometry, as is Goldmann tonometry. Numerous studies have shown the reliability of this technique but problems still exist. METHOD: We measured intraocular pressure (IOP) in 340 patients (668 eyes) with NCT and Goldmann tonometer (GAT). To evaluate the influence of central corneal thickness (CCT), we classified the patients according to their CCT (<500 microm; between 520 and 580 microm, and>600 microm). RESULTS: The mean difference between the two IOP measurements was -1.4 mmHg +/- 2.67 (-12 to +7), p<0,0001 for the thinner corneas, +0.13 mmHg +/- 2.67 (-8 to +8), p=0.445 for the regular corneas, and + 3.04 mmHg +/- 3.2 (-7 to +13) p<0.0001 for the thicker corneas. CCT influences NCT and GAT, but the difference between the two techniques is higher for thicker CCTs, higher IOPs, and in younger patients. CONCLUSION: NCT is good for glaucoma screening but is less reliable than GAT for glaucoma follow-up if CCT and IOP are far from regular values.

[Diode laser in "Malignant Glaucoma" treatment]. / Le laser Diode dans le traitement du "Glaucome Malin".

UNLABELLED: Malignant glaucoma remains one of the most dramatic complications of ocular surgery. It can occur after glaucoma surgery but also after iridotomy, capsulotomy, or cataract extraction. However, the mechanisms remain unclear. PURPOSE: to evaluate diode laser cyclodestruction as a complementary treatment in refractory malignant glaucoma. PATIENTS: Seven women with malignant glaucoma with onset several months before (mean, 43 months; range, 12-96 months), in whom shallow anterior chamber and high IOP (25 mmHg +/- 5.5 treated with 2.86 +/- 0.9 topical and systemic medications) persisted despite prior surgical treatment (mean, 2; range, 1-5). Controlateral eyes had hyperopia (mean, +3.7 D, range, +1 to +6), five had shallow anterior chamber and high IOP. UBM detected plateau iris in four women. METHODS: Seven eyes with malignant glaucoma and three controlateral eyes underwent cyclodestruction with diode laser (Viridis Twin Quantel Medical, laser, 810 nm), 22 burns around 270 degrees , 2 mm from the limbus for glaucomatous eyes and 15 inferior burns for controlateral eyes. RESULTS: Resolution of malignant glaucoma, with lower pressure (mean, 35%; range, 10%-70%), lower levels of medications (64%), final IOP at 13.2 mmHg (+/- 4.7), and deepening anterior chamber was achieved in all cases (mean follow-up, 18 months; range, 12-22). Cycloplegic topical treatment was stopped in 70% of cases. CONCLUSION: Diode laser cyclodestruction can help to resolve refractory malignant glaucoma. Larger UBM studies could help us to better understand the mechanisms of malignant glaucoma.

A faster way to characterize by triple-quantum-filtered (17)O NMR water molecules strongly bound to macromolecules in solution.

The simultaneous use of transverse and longitudinal relaxation rates, together with a transverse triple-quantum-filtering NMR sequence, was estimated for the adequate characterization of (17)O-water relaxation behavior in protein solutions. A complementary contribution to transverse relaxation was found, which was interpreted as chemical exchange of (17)O-water between different sites of the proteins. This contribution was estimated via calibration measurements. Then, for other similar samples, faster experiments could be performed. The analysis of the results obtained in this way gave adequate values of the relaxation rate of water in fast motion, of the fraction of water in slow motion, and of its correlation time. Hence, it permitted the complete characterization of the sample in a reasonable experimental time.