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Biomedical subjects

N Pfeiffer

Publications and source records attributed to N Pfeiffer.

126 records · Page 7Linked to original sources
PubMed1990

[The pattern electroretinogram in early glaucoma and ocular hypertension].

The pattern electroretinogram (PERG) reflects the activity of the retinal ganglion cells. To assess its value to detect early glaucoma damage, we recorded the PERG in 44 normal eyes, in 52 eyes with early stages of glaucoma, and in 34 eyes with elevated intraocular pressure but normal visual fields (ocular hypertension, OHT). All eyes had a decimal acuity of greater than or equal to 0.8. We used checkerboard patterns for the stimulation with check sizes of 0.8 degrees and 15 degrees, a contrast of 98% and a reversal rate of 16/s. Compared to the controls, in eyes with early glaucoma PERG amplitude was reduced to 50% using 0.8 degrees (p less than or equal to 0.0001) and to 74% using a check size of 15 degrees (p less than or equal to 0.001). However, due to the high interindividual variability, confidence limits overlapped to a large extent. Based on the preferential reduction at 0.8 degrees vs 15 degrees, a sensitivity of 74% and a specificity of 92% were achieved using a two-dimensional logistic regression; 50% of the OHT eyes were thus classified as pathological. These results suggest that the PERG can detect retinal ganglion cell damage before measurable changes in the visual field occur if responses to two check sizes are evaluated.

Adult↗
PubMed1990

[Local carbonic anhydrase inhibitors MK-927 and Mk-417. Effect and tolerance].

A comparative ocular tolerance study was undertaken with the topical carbonic anhydrase inhibitor (CAI) MK-927 (1% and 2%) and its S-enantiomer MK-417 (1% and 1.8%) in 20 healthy normal volunteers. In this randomized, double-blind cross over study, placebos were used for control over five periods. The subjects received one drop of placebo (common vehicle) or CAI in each eye in successive periods separated by a washout period of 1 week. Three hours after the dose, the IOP was found to be decreased by 5.3% to 9.1%, depending on the dose, with all four CAI treatments and significantly so with MK-417. Pupil-size and central vision were unchanged by CAIs. External and anterior segment examination revealed no changes following any of the treatments. The incidence of burning was significantly increased by 2% MK-927 (p less than 0.01) and 1.8% MK-417 (p less than 0.05) compared to placebo. The mean duration of burning placebo was 16.8 s, but it was significantly longer (23 to 37.1 s) following CAI application. Duration of tearing following CAI application was also significantly prolonged (p less than 0.05).

Adult↗
PubMed1990

[Decrease in intraocular pressure following administration of the local carbonic anhydrase inhibitor (MK-927)--comparison of the effect with pilocarpine].

We studied the effect of a single dose of the local carbonic anhydrase inhibitor, MK-927, on lowering IOP in 24 patients with bilateral primary open-angle glaucoma or ocular hypertension and compared it with the effect of pilocarpin in 9 patients. Following a washout of any glaucoma medication of 3 to 14 days, a diurnal IOP curve was performed. Two to seven days later one eye received a single drop of 2% MK-927 while the other eye received placebo and the diurnal IOP curve was repeated. MK-927 treated eyes showed a peak mean IOP change of 10.5 mmHg (33.1%) occurring at 4.5 h postmedication. In nine eyes treated with pilocarpin 1% q.d., the mean reduction of the mean IOP was 7.0 mmHg (22.1%) compared to no treatment. The same eyes showed a mean reduction of mean IOP of 6.1 mmHg (18.9%) following a single dose of MK-927. In contrast, the mean reduction of the maximal IOP treated with pilocarpin was 7.3 mmHg (25.8%) and 10.2 mmHg (34.2%) following MK-927. Considering the IOP lowering of MK-927 shown here, the possibility of a topically effective glaucoma therapy by local carbonic anhydrase inhibitor seems to be established. The IOP lowering effect of MK-927 appears to be similar to that of pilocarpin 1%.

Carbonic Anhydrase Inhibitors↗
PubMed1989

Limbus-based versus Fornix-based conjunctival flap in filtering surgery. A randomized prospective study.

A randomized prospective study was performed to compare the results of filtering surgery using a Limbus-based versus a Fornix-based conjunctival flap. The wound closure of the Fornix-based flap was performed using a running 10/0 nylon suture at the limbus. No statistical significant difference of IOP regulation was found between the two groups. There was a tendency of reduced occurrence of shallow anterior chamber and of less vascularized filtering blebs in the Fornix-based technique.

Conjunctiva↗
PubMed1989

[Treatment of glaucoma chronicum simplex with a combination of 0.5 percent timolol with 0.5 percent adrenaline plus 0.3 percent guanethidine].

The effect on the intraocular pressure of patients with primary open-angle glaucoma of a combination of timolol 0.5% with epinephrine 0.5% plus guanethidine 3% was studied and compared with the effects of timolol alone, of epinephrine 0.5% plus guanethidine 3%, and of other glaucoma drugs. The combination of timolol 0.5% with epinephrine 0.5% plus guanethidine 3% had a stronger effect on intraocular pressure (reduction 10.9 +/- 1.1 mm Hg) than epinephrine 0.5% plus guanethidine 3% (7.6 +/- 0.9 mm Hg) or timolol alone (5.8 +/- 1.1 mm Hg) or other glaucoma drugs. However, when the three substances are administered in combination therapy may show an addition of both pressure-lowering and side effects.

Clinical Trials as Topic↗
PubMed1985

Presynaptic opioid receptor subtypes in the rabbit ear artery.

In segments of rabbit ear arteries preincubated with [3H]noradrenaline, Leu-enkephalin, D-Ala2-D-Leu-enkephalin and ethylketocyclazocine concentration dependently reduced the overflow of tritium and the vasoconstriction elicited by field stimulation (120 pulses every 14 min, 1 Hz, 0.3 msec pulse duration). The effects of Leu-enkephalin and ethylketocyclazocine were antagonized by naloxone which, given alone, increased the evoked overflow of tritium at the high concentration of 10 microM. Morphine failed to produce inhibition, and at 100 microM actually increased evoked 3H-overflow. Continued exposure to Leu-enkephalin desensitized the tissue to this opioid; there was no cross-desensitization to ethylketocyclazocine. In arteries not preincubated with [3H]noradrenaline, normorphine, fentanyl and morphiceptin did not change the vasoconstrictor response (5 pulses every min, 5 Hz, 0.3 msec pulse duration). Among various peptide agonists, Leu-enkephalin, D-Ala2-D-Leu-enkephalin and Met-enkephalin were the most potent inhibitors. In a series of peptides with C-terminal extensions of the Met-enkephalin chain, the potency decreased in the order Met-enkephalin greater than Met-enkephalin-Arg-Gly-Leu greater than Met-enkephalin-Arg-Phe greater than BAM-12P greater than beta-endorphin. In a series of peptides with C-terminal extensions of the Leu-enkephalin chain, the potency decreased in the order Leu-enkephalin greater than dynorphin1-13 greater than dynorphin1-9 greater than alpha-neo-endorphin greater than dynorphin1-8 greater than dynorphin1-6 greater than dynorphin1-17. The delta-selective antagonist ICI 154129 counteracted the effect of Met-enkephalin but not that of dynorphin1-13, whereas naloxone counteracted the effect of either agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Presynaptic opioid receptors in the rabbit ear artery.

The effect of opioids was compared on field stimulation-induced 3H-noradrenaline overflow and vasoconstriction in the rabbit ear artery. Subtype-selective opioids were used, namely the mu-receptor agonist morphine, the delta-receptor agonist Leu-enkephalin and the kappa-receptor agonists ethylketocyclazocine and dynorphin1-13. Morphine (10 and 100 microM) exerted no inhibitory effect. The delta- and kappa-agonists depressed both the stimulation-evoked overflow and the vasoconstrictor responses with a similar potency. Naloxone prevented the effect of the respective agonists and in the same concentration range (3-10 microM) slightly increased transmitter release. During a continuous exposure of the preparation to Leu-enkephalin (0.1 microM) specific desensitization developed towards a higher concentration of this neuropeptide (1 microM), whereas the inhibition produced by ethylketocyclazocine (1 x microM) was unaffected. Exogenous and endogenous opioids may modulate transmitter release and in consequence vasoconstriction in the rabbit ear artery by acting on neuronal delta- and kappa-receptors.

Animals↗
PubMedDate not supplied

Dorzolamide: development and clinical application of a topical carbonic anhydrase inhibitor.

Systemic carbonic anhydrase inhibitors are among the most powerful agents to lower intraocular pressure. Unfortunately, their use is frequently accompanied by undesired side effects. Some are due to the relatively large amounts of drug that have to be systemically administered to inhibit the carbonic anhydrase in the ciliary processes. Recently, dorzolamide, a topical carbonic anhydrase inhibitor, has become commercially available for clinical use. This article reviews the development of topical carbonic anhydrase inhibitors with special reference to dorzolamide. When administered three-times daily, dorzolamide lowers intraocular pressure in a clinically useful manner. Ocular side-effects include frequent stinging and burning and allergy can develop. Systemic side effects have not been observed that could definitively be related to inhibition of extraocular carbonic anhydrase. Blood dyscrasias have not yet been observed. Absence of cardiovascular and pulmonary side effects, as can occur with beta adrenergic antagonists, and lack of pupillary and accommodative stimulation, as occur with cholinergic agonists, might make dorzolamide first-line medical treatment for elevated intraocular pressure.

Administration, Topical↗
PubMedDate not supplied

Effects of secondary flow caused by a curved channel on plasma protein adsorption to artificial surfaces.

The effects of secondary flow induced by a curved channel on fibrinogen deposition and replacement on a glass surface were studied. Platelet adhesion to surface-bound fibrinogen was also studied to indicate how secondary flow may affect thrombogenesis on artificial surfaces. A saline pre-wetted channel with straight and curved sections was exposed to flowing plasma at a Reynolds number of 28.6. Results show that fibrinogen deposited on the surface at a shear rate of 175 s-1 was replaced faster in regions of secondary flow (Dean numbers from 11 to 19) than in adjacent regions of shear flow. Platelets adhered only to those surfaces where fibrinogen had been detected.

Adsorption↗
PubMedDate not supplied

Analysis of the antibody repertoire in tears of dry-eye patients.

PURPOSE: It has recently been suggested that dry-eye disease has an underlying autoimmune mechanism. This hypothesis is further supported by the successful treatment of the disease with immunomodulatory drugs such as cyclosporin A. Although it is known that tears contain antibodies, very little is known about the antibody repertoires in tears. It was the aim of this study to analyze the IgA antibody repertoire against ocular antigens in the tears of patients suffering from dry-eye disease and compare it to those of healthy volunteers. METHODS: Two groups were examined: 20 healthy volunteers (controls) and 28 patients suffering from dry-eye disease. The patients were grouped according to the results of the basic secretory test. Patients with values < or =10 and subjective symptoms were classified as dry-eye patients. All tears were tested against Western blots of ocular antigens. For each Western blot, a densitograph was built by digital image analysis, and subsequently a multivariate discriminate analysis was performed. RESULTS: A complex staining pattern was found in the tears of both dry-eye patients and healthy controls. However, the number of peaks was statistically significantly increased (p < 0.05) in the tears of dry-eye patients. The discriminant analysis found a statistically significant difference between the antibody repertoires of both groups (Wilks' lambda = 0.11; p < 0.001). CONCLUSIONS: In this study, it could be shown that the complex antibody repertoires in the tears of patients suffering from dry-eye disease are different from those found in the tears of healthy volunteers. Thus, our findings support the hypothesis that the dry eye disease has an autoimmune mechanism.

Autoantibodies↗
PubMedDate not supplied

Vacuoles in the Acrysof intraocular lens as factor of the presence of serum in aqueous humor.

OBJECTIVE: Acrysoftrade mark (Alcon) foldable lenses (IOLs) have been shown to be highly biocompatible and exhibit a low incidence of posterior capsular opacification. However, minute vacuoles or 'glistenings' have been observed in some Acrysof IOLs. The clinical relevance of vacuole formation is presently unclear. To help clarify the influence of factors present under in vivo conditions on vacuole formation, the present experimental study examines the influence of aqueous humor components on the occurrence of vacuoles in Acrysof IOLs. METHODS: A total of 12 sterile Acrysof IOLs (Alcon, MA60BM) were incubated at body temperature (37 degrees C) for 3 or 6 months in anterior-chamber aqueous humor with or without human serum. The center portion was cut from two unconditioned, unhydrated, sterile control IOLs and the 12 conditioned IOLs and examined using light microscopy for vacuole formation. A third unconditioned, hydrated control IOL was examined using light and scanning electron microscopy. MEASURES: The incidence of vacuoles was quantified by two independent investigators using light microscopy. After hydration with balanced salt solution, the surface quality of a control IOL was examined using scanning electron microscopy. RESULTS: The control IOLs exhibited no or very few vacuoles. Scanning electron microscopy revealed that the control IOLs had normal surface texture without any surface vacuoles. IOLs that had been conditioned in aqueous humor without serum exhibited no great increase in the number of vacuoles, whereas IOLs conditioned in aqueous humor with serum exhibited a greater number of vacuoles that increased over time. CONCLUSIONS: The number of vacuoles increases with incubation time in aqueous humor containing serum. The addition of serum increased the proportion of lipids and proteins in the solution, which also occurs with a breakdown in the blood-aqueous barrier. The results of the present study point to a physiological factor that may lead to vacuole formation in IOLs and may aid clinicians in identifying risk factors involved in the formation of vacuoles.

Acrylates↗
PubMedDate not supplied

Physicochemical surface properties of various intraocular lenses.

PURPOSE: It is of major interest to understand how intraocular lens (IOL) surfaces interact with aqueous humor or tissues after implantation. Important parameters to describe the physicochemical surface properties are the contact angle and critical surface tension. Therefore, we performed measurements of the contact angle and critical surface tension of several commercially available IOLs. SETTING: Department of Ophthalmology, Johannes Gutenberg University, Mainz, University Eye Hospital, Tübingen, and Max Planck Institute for Polymer Research, Mainz, Germany. METHODS: A total of 17 commercially available standard quality IOL types (6 of each) of different materials from several manufacturers were studied. Scanning electron microscopy and contact angle measurements using the sessile drop method were made. RESULTS: The sessile drop method differentiated all materials based on their surface forces. The contact angle (mean +/- SD) ranged from 56.5 +/- 3.8b 3. CONCLUSION: Contact angles differed between the IOLs depending on the IOL material with the lowest contact angle in the heparin-surface-modified IOL. The contact angle measurement method generates useful information about the material surface and its potential biomaterial interactions.

Acrylic Resins↗
PubMedDate not supplied

Allopurinol has immunomodulating activity following topical and systemic application in experimental autoimmune uveitis.

PURPOSE: Allopurinol has beneficial effects in the systemic treatment of lens-induced uveitis and experimental autoimmune uveitis (EAU). This is believed to be due to a reduction of oxidative tissue damage through its dose-dependent free radical scavenging ability, and to an immunomodulating effect. The purpose of this study was to demonstrate the immunological effects on the IgG-antibody repertoire in EAU after topical and systemic allopurinol and steroids. METHODS: We assigned 43 male Lewis rats to 6 different groups: healthy rats (BASE, n=3)

Adjuvants, Immunologic↗
PubMedDate not supplied

Analysis of autoantibody repertoires in sera of patients with glaucoma.

PURPOSE: Glaucoma is the second cause of blindness worldwide. It is usually considered a neurodegenerative disease. There is evidence that an autoimmune mechanism is involved in the development of glaucoma in some patients. The aim of this study was to analyze the IgG autoantibody repertoires in sera of glaucoma patients and healthy subjects. METHODS: A total of 82 patients were divided into four groups: healthy volunteers without any ocular disorders (CO, n = 30), patients with primary open-angle glaucoma (POAG, n = 19), ocular hypertension (OHT, n = 16), and normal tension glaucoma (NTG, n = 17). All groups were matched for age and gender. The sera of these patients were tested against Western blots of retinal antigens. Immunodetection was done using 4-chloro-1-naphthol staining. The autoantibody patterns were digitized and subsequently analyzed by multivariate statistical techniques. RESULTS: All patients showed different, complex staining patterns of autoantibodies against retinal antigens. There was an increase in the number of peaks in sera of patients with primary open-angle glaucoma (POAG) compared to healthy subjects (CO). Including all peaks the analysis of discriminance revealed a statistically significant difference between the patterns of POAG compared to all other groups (p < 0.01). Sera of normal tension glaucoma (NTG) had no statistically different autoantibody pattern compared to those of control subjects. CONCLUSIONS: In this study, we demonstrated a difference in the IgG autoantibody patterns of primary open-angle glaucoma patients compared to healthy subjects. However, the patterns were not significantly different in normal tension glaucoma compared to control subjects.

Aged↗
PubMedDate not supplied

Glaucoma detection using the GDx nerve fiber analyzer and the retinal thickness analyzer (RTA).

PURPOSE: To compare the ability of the nerve fiber analyzer (GDx) and the retinal thickness analyzer (RTA) to discriminate between glaucomatous and healthy eyes. METHODS: Thirty-seven glaucoma patients (early to moderate severity) and 34 healthy controls were included. Glaucoma patients were defined as those with two repeatable abnormal visual fields by automated perimetry within 1 year. All subjects were examined with a GDx scanning laser polarimeter and RTA. Twelve GDx retinal nerve fiber layer parameters and 12 RTA optic disk topography parameters were obtained. GDx and RTA measurements were compared between both experimental groups using t-tests. Areas under the receiver operating characteristic curves (AUROC) for discriminating between healthy and glaucomatous eyes using GDx and RTA parameters were calculated and compared, and sensitivities at >or=80% and >or=95% specificity were reported. RESULTS: Statistically significant differences between glaucomatous and healthy eyes were found for most GDx and RTA parameters. For GDx, the parameter with the largest AUROC for discriminating between healthy and glaucomatous eyes was the number (AUROC = 0.91, sensitivity = 85% at specificity = 84%, sensitivity = 73% at specificity = 95%). For RTA, the parameter with the largest AUROC was mean cup depth (AUROC = 0.79, sensitivity = 61% at specificity = 82%, sensitivity = 33% at specificity = 95%). The AUROC for the GDx number was significantly larger than the AUROC for RTA mean cup depth (p<0.05). CONCLUSIONS: GDx showed better discrimination and better sensitivities at fixed specificities than RTA. The currently available RTA optic disk analysis software likely cannot replace GDx RNFL analysis software for successful glaucoma diagnosis.

Area Under Curve↗
PubMedDate not supplied

Scanning laser polarimetry and retinal thickness analysis before and after laser in situ keratomileusis.

PURPOSE: To evaluate changes in retinal nerve fiber layer (RNFL) thickness after laser in situ keratomileusis (LASIK) using a scanning laser polarimeter with fixed corneal compensation (GDx) and the retinal thickness analyzer (RTA). METHODS: Thirty-eight eyes of 19 healthy subjects (10 female and 9 male; mean age 37.0-/+8.8 years) underwent GDx and RTA measurements before and after LASIK. All subjects revealed mild to high myopia (mean spherical refraction: -4.0-/+2.75 D). Measurements using GDx were followed by RTA measurements after pupil dilation. All measurements were performed the day before LASIK and 1 week postoperatively. RESULTS: GDx revealed a decrease in nerve fiber layer thickness measurements after LASIK, but did not reach statistical significance (p>0.05). Using RTA, mean RNFL thickness (MRNFL) and RNFL cross sectional area decreased significantly after LASIK (p=0.03 and p=0.02, respectively). CONCLUSIONS: Scanning laser polarimetry revealed a slight decrease in RNFL thickness measurements after LASIK. MRNFL and RNFL cross section were significantly lower after LASIK using RTA. The changes might be artifacts in a small group of myopic subjects.

Adult↗