Ria Beck

Improved penetration of aminoglycosides and fluoroquinolones into the aqueous humour of patients by means of Acuvue contact lenses

AbstractObjectives: In order to improve the penetration of topically applied drugs in ophthalmology, the suitability of hydrophilic contact lenses (Acuvue, Vistacon, power −1.0 D) as a drug delivery system for antibiotics was tested. A prospective study was undertaken to determine the transcorneal penetration of five topically applied aminoglycosides and fluoroquinolones into the aqueous humour of patients. Methods: Two hundred and sixty-five patients undergoing cataract extraction received 0.3% gentamicin, kanamycin, tobramycin, ciprofloxacin or ofloxacin solution by two different modes of administration: either as eye drops (nine drops every 15 min, starting 2 h prior to surgery) or by means of a drug delivery system (Acuvue contact lenses soaked for 1 h in eye drop solution without preservatives, 1–5 h prior to surgery). At the beginning of cataract extraction, 50–100 μl aqueous fluid was aspirated from the anterior chamber and immediately stored at −80 °C. Antibiotic concentrations were measured using fluorescence polarisation immuno-assays (aminoglycosides) or high-performance liquid chromatography (fluoroquinolones). Results: After soaking for 1 h in 0.3% eye drop solutions, Acuvue contact lenses released about 190–250 μg aminoglycoside and ofloxacin and 1000 μg ciprofloxacin. These amounts are considerably lower or in the same order of magnitude than obtained with application of eye drops (1350 μg).From the aminoglycosides tested, only gentamicin and tobramycin, but not kanamycin, were able to penetrate into the aqueous humour of patients. After the wearing of antibiotic-soaked lenses, mean aqueous humour concentrations were higher than after the use of eye drops. This difference reached significance in tobramycin (1.09 (1.30) μg · ml−1 vs 0.49 (0.79) μg · ml−1), ciprofloxacin (1.23 (0.60) μg · ml−1 vs 0.38 (0.33) μg · ml−1) and ofloxacin (5.55 (2.53) μg · ml−1 vs 0.56 (0.37) μg · ml−1).The percentage of patients with aqueous humour concentration above the MIC90 of Staphylococcus epidermidis, the most common cause of postoperative endophthalmitis, was 92% and 100% after wearing ciprofloxacin- or ofloxacin-soaked lenses, respectively. Conclusion: Gentamicin and tobramycin penetrated into the aqueous humour of patients, whereas kanamycin was not able to overcome the corneal barrier. Acuvue contact lenses soaked in 0.3% eye drop solutions can release sufficient amounts of gentamicin, ciprofloxacin and ofloxacin to produce bacteriostatic concentrations in the humor aquosus. Acuvue contact lenses can be recommended as a drug delivery system for fluoroquinolones.

Penetration of ciprofloxacin, norfloxacin and ofloxacin into the aqueous humor using different topical application modes

Abstract · Background: A prospective study was undertaken to determine the transcorneal penetration of three topically applied fluoroquinolones into aqueous humor. · Methods: Cataract patients (n=224) preoperatively received topically applied gyrase inhibitors (0.3% ciprofloxacin, 0.3% norfloxacin, 0.3% ofloxacin) in two different application modes. In application mode I, patients received on the day before operation 3×1 eye drop at 2-h intervals, and on the day of operation 3 drops at 1-h intervals. In application mode II, patients received 9 drops at 15-min intervals on the day of operation only. Just before cataract surgery 50–100 μl aqueous humor was aspirated and stored at –80 °C. The HPLC method was used for measuring the concentration. · Results: The highest concentrations of all tested antibiotics were measured after the mode of application in which one drop was given every 15 min between 06:00 and 08:00 hours before operation. In this mode, ciprofloxacin achieved a mean aqueous level of 379.8±327.8 μg/l (range 33–1388 μg/l), norfloxacin 182.1±118.1 μg/l (range 38–480 μg/l) and ofloxacin 563.9±372.1 μg/l (range 64–1455 μg/l). These mean concentration are all above the MIC90 of gram-negative bacteria like Proteus mirabilis and Escherichia coli. In some cases the concentrations of ciprofloxacin and ofloxacin, but never norfloxacin, reached therapeutic values above the MIC90 of Staphylococcus aureus and Staphylococcus epidermidis · Conclusions: The mean concentration value of 0.3% ciprofloxacin and of 0.3% ofloxacin in the aqueous humor reached the MIC90 values of the frequently occurring gram-positive and gram-negative bacteria. Of the currently available topical fluoroquinolones, ofloxacin achieved the highest aqueous humor concentration. Considering the higher antimicrobial activity of ciprofloxacin, both ciprofloxacin and ofloxacin may be useful ophthalmic agents in antibacterial management, but they are not efficient against Streptococcus pneumoniae and Pseudomonas aeruginosa.

Corneal and conjunctival findings after mitomycin C application in pterygium surgery: an in‐vivo confocal microscopy study

Purpose:  To perform a qualitative assessment of the topical side‐effects of mitomycin C on cornea after pterygium surgery.

Analysis of aqueous humour proteins of eyes with and without pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PEX) has been suggested to represent a blood-aqueous barrier impairment leading to a higher protein content in aqueous humour of eyes with PEX. However, the nature of a prospective PEX protein has not yet been described. We set out to re-evaluate protein content and examine protein composition for prospective PEX protein candidates in aqueous humour of eyes with PEX syndrome. Aqueous humour of 52 patients with PEX and 38 without PEX signs was sampled during cataract or glaucoma surgery. Total aqueous protein concentration in the samples was analysed in 43 PEX specimens and 32 non-PEX specimens according to Bradford. Aqueous protein composition of all samples was determined by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS PAGE) and silver staining. Screening for amyloids was performed in nine PEX samples and six non-PEX samples by Congo Red staining and polarised light microscopy. Aqueous protein concentration was not significantly increased in PEX eyes in comparison with non-PEX eyes. Furthermore, we could not detect any characteristic difference in protein band sizes of the two groups after SDS PAGE. However, we were able to show the presence of amyloid exclusively in aqueous humour of PEX patients. Conclusion: our results do not confirm a generally higher protein concentration in pseudoexfoliation syndrome eyes. This does not necessarily contradict a blood-aqueous barrier impairment but illustrates the variance in protein concentration between and within the two groups. No characteristic protein band allocatable to pseudoexfoliation syndrome proteins could be detected in any of the samples. However, our findings support the theory that the pseudoexfoliation syndrome is associated with an amyloid of a serum protein.

Pharmacological-induced haptic changes and the accommodative performance in patients with the AT-45 accommodative IOL

PURPOSE To investigate the accommodative performance of the AT-45 (eyeonics Inc, Aliso Viejo, Calif) using three-dimensional ultrasound biomicroscopy. METHODS The AT-45 haptic region was visualized in vivo 1 month after surgery in four patients using an in-house developed three-dimensional ultrasound biomicroscope. Haptic changes, axial shift, and accommodation amplitude were determined under pharmacologically induced accommodation. RESULTS The angulation, depending on the accommodation state, could be distinguished and analyzed. In vivo a mean change in haptic angulation of 3.3 +/- 3.3 degrees (range: 0 degrees to 7 degrees) and a mean forward shift of 0.13 +/- 0.08 mm (range: 0.05 to 0.2 mm) were observed for the AT-45 using pharmacologically induced accommodation. A mean accommodative amplitude of 0.44 +/- 0.24 diopters (D) (range: 0.25 to 0.75 D) was found using a Hartinger coincidence refractometer. CONCLUSIONS Minimal angulation changes and axial movements of the AT-45 have been demonstrated using pharmacological stimulation and objective measurement methods. The mechanical performance of the AT-45 in these eyes does not appear to provide the range of accommodation necessary for close work.

Influence of Benzalkonium Chloride on Langerhans Cells in Corneal Epithelium and Development of Dry Eye in Healthy Volunteers

Purpose: To investigate the influence of benzalkonium chloride (BAC) on corneal Langerhans cells (LCs) and on the development of dry eye. Methods: A randomized double-blind clinical trial was performed in 20 healthy volunteers. One eye of each subject was treated with a 0.01% BAC solution (and the fellow eye with a placebo solution) three times daily for 12 weeks. The distribution and density of LCs in the central and peripheral corneal epithelium were evaluated by in-vivo confocal laser-scanning microscopy (CLSM). The subjects were monitored for dry eye (subjective discomfort, slit-lamp biomicroscopy, tear film break-up time, Schirmer’s test). Results: In the BAC group, compared with placebo, a marked increase in LC density was found in the central cornea at Week 6 and in the central and peripheral cornea at Week 12. LC density then decreased again in both zones after the end of treatment, falling toward (or even below) baseline levels. Significant changes in the LC count relative to baseline were found at Week 12 in the central and peripheral cornea in the BAC group as well as in the peripheral cornea in the placebo group. LC density in the BAC group increased more rapidly in the central than in the peripheral cornea. During therapy the BAC group showed no signs of dry eye. Conclusion: 12-week application of a 0.01% BAC solution in healthy volunteers induces a significant increase in LCs in the central cornea at Week 12 without dry-eye changes. The return of LC counts toward (or even below) baseline levels just four weeks after the end of BAC administration demonstrates the rapid normalization of the inflammatory environment.

Adherence of staphylococci to various intraocular lenses with different levels of hydrophobicity

Background: A major goal in research on intraocular lenses (IOL) is the development of new polymers and modifications to reduce foreign-body reactions after implantation. This effect may be achieved by a reduction in the surface hydrophobicity of the polymers. To illustrate the influence of surface modifications on bacterial adhesiveness, the most often isolated organism in “low-grade” postoperative endophthalmitis, Staphylococcus epidermidis, was used. Materials and methods: For this reason three strains of this species, the type strain ATCC 14990 and two clinical isolates (8687, 6579 I) with different hydrophobic surface properties were studied. IOL, used in the experiments were either made of PMMA or silicone with modified surfaces (unpolished, polished, heparinized). The adhesiveness of H3-thymidin-labeled bacteria was calculated/mm2 of lens surface. Each experiment was performed in triplicate and repeated three times. Results: The hydrophobic-type strain showed stronger adherence to unpolished PMMA surface (8000 bacteria per mm2) compared to the polished (5200 bacteria/mm2). In contrast, the hydrophilic strain adhered with 2000 bacteria/mm2 to the unpolished and with 4200 bacteria/mm2 to the polished surface. Polishing PMMA lenses diminished the differences between the three strains. However, surface passivation of silicone lenses increased the adhesion rate of the hydrophilic strain up to 9600 bacteria/mm2. Treatment of PMMA lenses with heparin increased the adhesiveness of the hydrophilic strain and reduced the adhesion rate of the hydrophobic type strain to 250 bacteria/mm2. Conclusions: It was demonstrated that bacterial adherence to IOL also involves hydrophobic interactions. Obviously, however, that adherence reflects a complex of interactions between the two surfaces.Fragestellung: Ein Hauptziel in der Entwicklung von Intraokularlinsen (IOL) ist die Anwendung neuer Polymere und Modifikationen zur Reduzierung von Fremdkörperreaktionen. Dies kann durch eine Verminderung der Oberflächenhydrophobizität der Polymere erreicht werden. Inwieweit eine Oberflächenmodifizierung auch die bakterielle Haftung beeinträchtigt, soll mit dem am häufigsten bei Low-grade-Endophthalmitiden isolierten Keim Staphylococcus epidermidis untersucht werden. Material und Methode: Für die Untersuchungen wurden 3 Staphylococcus-epidermidis -Stämme, ATCC 14990 und 2 klinische Isolate (8687, 6579 I) mit unterschiedlicher Hydrophobizität und verschiedene IOL (PMMA, Silikon) mit unterschiedlichen Oberflächenmodifikationen (unpoliert, poliert, heparinisiert) ausgewählt. Die Haftung von H3-Thymidin-markierten Bakterien wurde auf mm2 Linsenoberfläche berechnet. Aufgrund bekannter Schwankungen bei Adhärenzuntersuchungen wurden pro Bakterienstamm und Versuch 3 Linsen parallel getestet und jeder Versuch insgesamt 3 mal an 3 verschiedenen Tagen durchgeführt, so daß pro Stamm 9 Einzelwerte erhalten wurden. Ergebnisse: Der hydrophobe Stamm zeigte eine stärkere Haftung an unpolierten (8000 Bakterien/mm2) als an polierten PMMA-Linsen (5200 Bakterien/mm2). Im Gegensatz dazu adhärierte der hydrophile Stamm mit 2000 Bakterien/mm2 an unpolierten und mit 4200 Bakterien/mm2 an polierten Oberflächen. Die Polierung von PMMA-Linsen reduzierte die Differenzen in der Haftung der 3 Staphylococcus-epidermidis -Stämme unterschiedlicher Hydrophobizität. Bei der Verwendung von Silikonlinsen stieg die Anzahl adhärierter Bakterien des hydrophilen Stamms auf 9600 Bakterien/mm2. Die Oberflächenmodifizierung von PMMA-Linsen mit Heparin verstärkte die Haftung des hydrophilen Stamms und führte zu einer Adhärenzreduzierung des hydrophoben Stamms auf 250 Bakterien/mm2. Schlußfolgerung: Es konnte gezeigt werden, daß in die bakterielle Adhärenz an IOL auch hydrophobe Wechselwirkungen integriert sind. Offensichtlich handelt es sich jedoch um ein komplexes Wechselspiel zwischen beiden Oberflächen.

Importance of calcium and potassium currents in human lens epithelial cells (hLEC) and the effect of the calcium channel blocker mibefradil

Background: To prevent posterior capsule opacification (PCO), we followed the hypothesis that calcium channel blockers (antagonists) interfere with integrin signaling and block cell adhesion in lens epithelial cells (LEC). In primary human LEC we found that the T channel antagonist mibefradil induces apoptosis which was accompanied with cell shape changes and loss of cell adhesion. Although T-type calcium channels are substantially present in membranes of freshly dispersed primary cultured hLEC and calcium currents are inhibited by mibefradil at concentrations of 10-8 M, the antiproliferative site of action of this drug remains unclear, since this feature is observed at concentrations 200-fold higher than that for calcium channel blockade. Methods: Epithelial cells of the human lens were dispersed by enzymatic treatment, recordings of membrane currents were performed using patch clamp technique in the whole cell configuration. Westernblot analysis was used for protein detection. Results: Total current elicited on depolarizing voltage steps from a holding potential of-80 mV was composed of inward (calcium) and outward (potassium) current. Outward current could be inhibited mostly by intracellular application of cesium ions. Currents in inward direction were activated fast (< 2 ms) and inactivated during the following 20 ms. They were characterized as calcium currents since the known calcium channel inhibitor nifedipine blocked these currents in a concentration-dependent manner. Using potassium in the pipette (145 mM) as main charge carrier, additionally a noninactivating potassium current and a voltage- and time-dependent potassium current which slowly inactivated (Kv) were observed (control). Adding mibefradil in concentrations from 10-6 M - 10-5 M to the bath solution, the inwardly directed and the non-inactivating current component were inhibited concentration-dependent. The Kv component was affected in a similar way, however, this component showed an increased inactivation behavior after application of mibefradil in the named concentrations. Conclusion: The total effects of mibefradil are significant for the calcium homeostasis since calcium current itself is inhibited but, moreover, the membrane is permanently depolarized up to 20 mV by the drug. Both effects may contribute to the observed reduced cell adhesion during mibefradil treatment. (Less)

Ein 3-D-Kapselsackmodell zur Beschreibung der biomechanischen Eigenschaften neuer Kunstlinsentypen

ZusammenfassungHintergrund. Zur Bestimmung einer eventuellen Verformung des Kapselsackes nach Implantation von. Intraokularlinsen (IOL) aus unterschiedlichem Material und Design wurde mit Hilfe einer geeigneten Preßvorrichtung aus Silikonkautschuck ein 3-dimensionales Modell des Kapselsackes hergestellt. Material und Methode. Nach Einsetzen von 13 verschiedenen Intraokularlinsen aus PMMA, Silikon und Acrygel in den künstlichen Kapselsack wurden die Verformungsgrade mit Hilfe von Deformierungsquotienten und -faktoren bestimmt. Mit Hilfe des Ultraschallbiomikroskopes (UBM) wurde die Größe des Spaltes zur Kapselsackrückwand ermittelt. Ergebnisse. Intraokularlinsen aus PMMA mit C-Haptik-Design bewirkten eine relativ stärkere Verformung des Kapselsackes als Linsen aus Silikon. Beide Linsentypen zeigten einen relativ breiten Spalt zwischen Optik und Kapselsackrückwand. Intraokularlinsen aus Acrygel mit atypischen Haptikkonfigurationen oder C-Haptik erzielten bessere Ergebnisse hinsichtlich der Verformung und spaltfreier Lage der Optik zur Kapselsackrückwand. Schlussfolgerungen. Ein 3-D-Silikonkautschuckmodell ist geeignet, eine mögliche Verformung des Kapselsackes nach der Implantation einer IOL und die Lage der Optik zur Kapselsackrückwand außerhalb des Auges zu simulieren. Aus den gewonnenen Ergebnissen hinsichtlich der spaltfreien Lage der Optik zur Kapselsackrückwand könnte man Rückschlüsse auf die zu erwartende Nachstarentwicklung ziehen.AbstractBackground. This study quantified the geometric deformation of the capsular bag following implantation of various intraocular lenses (IOL) using a three-dimensional capsular bag model made of silicone caoutchouc. Methods. After implantation of 13 different IOLs (polymethylmethacrylate, silicone acrygel) into the artificial bag, the induced capsular bag deformation was measured and analyzed. The posterior space between IOL and capsule was examined by ultrasonographic biomicroscopy. Results. Polymethylmethacrylate IOLs with C-haptic design induced a greater deformation of the capsular bag than silicone lenses; however, both types showed a larger gap posterior to the IOL than acrygel lenses. Acrygel IOLs with different haptic design revealed only minimal deformation with close contact posteriorly. Conclusions. The presented three-dimensional model simulates the biomechanical and geometrical parameters of the vital capsular bag. Further investigations may determine a correlation of close posterior IOL contact and lens epithelial cell progression.

Mechanical ocular trauma

The problems related to mechanical ocular trauma must always be analyzed with the socioeconomic background of the population in mind. This theory applies to etiology, diagnostic and therapeutic procedures, as well as the final functional outcome. The literature published in 31 main ophthalmological journals in the last 12 months reflects different local factors, such as military activities of various technical levels, the degree of violence in so-called “civilized” countries, and the different spectrum of occupational accidents depending on the degree of preventive care.