Biomedical subjects

Anselm G Jünemann

Publications and source records attributed to Anselm G Jünemann.

7 recordsLinked to original sources

PubMed2006

Visual evoked potentials of the blue-sensitive pathway under cold provocation in normals and glaucomas.

BACKGROUND: Vascular dysregulation in open-angle glaucomas can be identified by measuring the blood circulation during exposure to cold water. Aim of this study was to find out whether the same cold stimulus would lead to functional changes in the visual evoked potentials (VEP) of the short-sensitive pathway in normals and glaucoma patients. PATIENTS AND METHODS: Blue-on-yellow pattern-visual evoked potentials were studied in 22 healthy control persons and 47 patients with primary open-angle glaucoma (25 high-pressure glaucomas, 22 normal pressure glaucomas with clinical signs of vasospastic hyperreactivity). A blue stripe pattern, presented in onset-offset mode on a yellow adaptation light served as the stimulus. Cold provocation was initiated by dipping one hand of the patient into cold water of 3 degrees C to 5 degrees C. The onset amplitudes and peak times were measured without cold exposition as well as two and four minutes after the cold exposition began. RESULTS: In the group of vasospastic glaucoma patients a significant reduction of visual evoked potential-amplitudes was observed during cold provocation (amplitude before ice exposition: 4.17 microV, amplitude following two minutes of ice exposition: 3.52 microV; paired test: P < 0.01). Other subject groups showed no significant amplitude reductions after cold provocation. Peak times of both open-angle glaucoma groups (132.3 +/- 18.7 milliseconds in high pressure, 132.7 +/- 14.5 milliseconds in normal pressure) were significantly increased in comparison to normals (117.4 +/- 8.0 milliseconds). However, no significant influence of the cold provocation on peak times could be found in all groups. CONCLUSION: Peak times of the blue-on-yellow visual evoked potentials are significantly prolonged in patients with primary open-angle glaucomas. Cold provocation causes a significant amplitude reduction of the blue-on-yellow visual evoked potential in the present normal-pressure glaucoma patients and reflects vascular dysregulation in patients with vasospastic hyperreactivity.

Blood Pressure↗

PubMed2006

Improving glaucoma diagnosis by the combination of perimetry and HRT measurements.

PURPOSE: The aim of this study was to determine, whether the combination of morphologic data of the optic nerve head and visual field (VF) data would improve diagnosis of glaucoma, on the basis of the measurements alone. PATIENTS AND METHODS: Eighty-eight perimetric glaucomatous and 88 normal optic discs from the Erlangen Glaucoma Registry were matched for age. All normals and patients were examined in a standardized manner (Slitlamp biomicroscopy, gonioscopy, 24 h-applanation tonometry, automated VF testing, 15-degree optic disc stereographs, and Heidelberg Retina Tomograph (HRT)-scanning of the optic disc). The HRT variables were calculated in 4 optic disc sectors. All variables were calculated with the software's standard reference plane. To gain the same allocation of sectors as provided by the HRT software, the VF responses were averaged within 4 sectors. Classification results of these VF responses were compared with the summarized results within 4 sectors. Six different combinations of morphologic and VF data were used to assess their suitability to diagnose the disease. HRT measurements, and the standard output of the Octopus (HRT/PERI1), HRT measurements and the summarized sectors and their standard deviations (HRT/PERI2), HRT measurements, standard output of the octopus and the summarized sectors and their standard deviations (HRT/PERI1/PERI2), standard output of the Octopus (PERI1), summarized sectors of the Octopus and their standard deviations (PERI2) and HRT measurements. To assess the diagnostic value of the different data sets machine learning classifiers, stabilized linear discriminant analysis, classification trees, bagging, and double-bagging were applied. RESULTS: Combination of morphologic and VF data improved the automated classification rules. The accuracy to diagnose glaucoma just by VF and HRT indices was maximized for double-bagging using both diagnostic tools. An estimated misclassification probability of less than 0.07 could be achieved for the primary open angle glaucoma patients combining HRT and VF sectors by double bagging. So highest sensitivity was 95% and specificity 91%, achieved by double-bagging and combination of HRT, PERI1, and PERI2. CONCLUSIONS: The combination of optic disc measurements and VF data could not only improve glaucoma diagnosis in future, but could also help to find an objective way to diagnose glaucomatous optic atrophy. The limitation of the topographic relationship between structure and function is the individual variability of the optic disc morphology and the subjective variability of VF testing.

Female↗

PubMed2006

Clusterin deficiency in eyes with pseudoexfoliation syndrome may be implicated in the aggregation and deposition of pseudoexfoliative material.

PURPOSE: To determine the role of the extracellular chaperone clusterin in the pathophysiology of pseudoexfoliation (PEX) syndrome/glaucoma, which is characterized by the stable deposition of abnormal extracellular fibrillar material in anterior segment tissues. METHODS: Real-time PCR, in situ hybridization, and immunohistochemistry were applied to analyze the mRNA and protein expression of clusterin in PEX eyes of patients without and with glaucoma and to compare them with eyes of patients with primary open-angle glaucoma and angle-closure glaucoma and with normal control eyes. Aqueous levels of clusterin were determined by Western blot analysis. Real-time PCR and Western blot analysis were used to study the effect of TGF-beta1, which is significantly increased in the aqueous humor of PEX eyes, on clusterin expression by nonpigmented ciliary epithelial cells in vitro. RESULTS: Clusterin mRNA was ubiquitously expressed in most ocular cells and tissues, particularly in the epithelium of ciliary processes, whereas the protein was mostly located to extracellular structures, such as ocular basement membranes and stromal fibers. Real-time PCR and in situ hybridization displayed significant downregulation of clusterin mRNA in all anterior segment tissues of PEX eyes, irrespective of the presence or type of glaucoma, compared with normal and glaucomatous control eyes, whereas posterior segment tissues did not show any differential expression. A generally decreased immunoreactivity, but a prominent binding of clusterin to all PEX deposits, could be observed in ocular tissues of PEX eyes. Clusterin levels in aqueous humor were significantly reduced in eyes of patients with PEX syndrome compared with normal and glaucomatous control eyes. The expression of clusterin mRNA and protein in nonpigmented ciliary epithelial cells was significantly downregulated by TGF-beta1 in vitro. CONCLUSIONS: Considering the known role of clusterin as a highly efficient extracellular chaperone, its deficiency in the anterior segment of PEX eyes may promote the stress-induced aggregation and stable deposition of the pathologic extracellular matrix product characteristic of PEX syndrome.

Aged↗

PubMed2005

Association between localized visual field losses and thickness deviation of the nerve fiber layer in glaucoma.

PURPOSE: To perform a correlation between morphology and function by studying local perimetric field losses and thickness reduction of the nerve layer in corresponding areas. METHOD: Forty-seven patients with "preperimetric" open-angle glaucoma, 95 patients with "perimetric" open-angle glaucoma, and 75 control subjects had perimetric (Octopus) and polarimetric measurements. Criteria for exclusion: optic discs larger than 4 mm, media opacities, polarimetric hourglass pattern in the macular image. Thickness values of the retinal nerve fiber layer were determined in 14 upper and 14 lower sectors (10 degrees each) as well as nasally and temporally (40 degrees each) as provided from the GDx (software version 4000). The healthy control subjects served to determine age-corrected thickness deviation in all sectors. Analyses were calculated in eight nerve fiber bundle related areas. Due to non-linear relationships between perimetric defects and corresponding thickness deviation non-parametric tests were used. RESULTS: Localized visual field defects in the present perimetric patients were highest in upper and lower visual field areas abutting the nasal meridian. Thickness loss of nerve fiber layer however was highest in more circumferential upper and lower nerve fiber bundles. Correlations between local mean defects and deviation of the retinal nerve fiber layer thickness from normals showed a clear association for corresponding areas. The correlation coefficients were significant (P < 0.01) for all arcuate superior and inferior visual field zones except horizontally and not for the area of the lower nasal step. CONCLUSION: The present correspondence map indicates that focal perimetric defects can be identified best polarimetrically if they occur in the arcuate bundles of the visual field. A lack of correspondence was observed in the area of the papillo-macular bundle.

Female↗

PubMed2003

Combined use of frequency doubling perimetry and polarimetric measurements of retinal nerve fiber layer in glaucoma detection.

PURPOSE: The aim of this study was to evaluate the diagnostic usefulness of the combined use of frequency-doubling technology (FDT) perimetry and polarimetry of the retinal nerve fiber layer. DESIGN: Cross-sectional study. METHODS: Seventy ocular hypertensive patients (normal optic disk and standard perimetry, elevated intraocular pressure [>21 mm Hg]), 59 patients with "preperimetric" open-angle glaucoma (glaucomatous optic disk atrophy, elevated intraocular pressure [>21 mm Hg], no visual field defect in standard perimetry), 105 patients with "perimetric" open-angle glaucoma (glaucomatous optic disk atrophy and clearly marked visual field defect), and 73 control subjects had FDT screening (protocol: C-20-5) and polarimetric measurements (GDx). Criteria for exclusion: optic disks larger than 4 mm(2), media opacities, patients younger than 33 years or older than 66 years. None of the subjects had earlier FDT perimetry. One eye of each patient and control subject entered the statistical evaluation. Database and statistical software were used for case-wise recalculation of all missed localized probability levels to create a FDT screening score. RESULTS: At a predefined specificity of 94.5% in control eyes, discrimination between "perimetric" glaucoma and normal subjects is superior using the FDT perimetry (sensitivity = 84.8%) in comparison to polarimetry (sensitivity = 63.8%), whereas sensitivity is similar with both methods in "preperimetric" patients (GDx, FDT: 25.4%). In several cases, patients classified as glaucomatous by the GDx are not the same patients as identified by the FDT perimetry. Therefore, a two-dimensional discrimination analysis can increase correct positive classification. Using a linear combination of the present FDT screening score and polarimetry ("the number"), 92.4% of "perimetric" glaucoma eyes and 44.1% of "preperimetric" glaucoma eyes have been classified as glaucomatous. CONCLUSION: Joint usage of polarimetry and FDT perimetry indicate that a combination of different techniques which can uncover different glaucoma properties, might be helpful in early glaucoma detection.

Cross-Sectional Studies↗

PubMed2003

New glaucoma classification method based on standard Heidelberg Retina Tomograph parameters by bagging classification trees.

PURPOSE: In this article we propose and evaluate nonparametric tree classifiers that can handle non-normal data and a large number of possible predictors using the full set of standard Heidelberg Retina Tomograph measurements for classifying glaucoma. METHODS: The classifiers were trained and tested using standard Heidelberg Retina Tomograph parameters from examinations of 98 subjects with glaucoma and 98 normal subjects of the Erlangen Glaucoma Registry. All patients and control subjects were evaluated by 15 degrees -optic disc stereographs, Heidelberg Retina Tomograph measurements, standard computerized white-in-white perimetry, and 24-hour-intraocular pressure profiles. The subjects were matched by age and sex. Standard classification trees as well as bagged classification trees were used. The classification outcome of the trees was compared with the classification by two published linear discriminant functions based on Heidelberg Retina Tomograph variables with respect to their cross-validated misclassification error. RESULTS: The bagged classification tree had the lowest misclassification error estimate of 14.8% with a sensitivity of 81.6% at a specificity of 88.8%. The cross-validated error rates of the two linear discriminant function procedures were 20.4% (sensitivity 82.6%, specificity 76.7%) and 20.6% (sensitivity 81.4%, specificity 77.3%) for our set of observations. Bagged classification trees were able to reduce the misclassification error of glaucoma classification. CONCLUSIONS: Bagged classification trees promise to be a new and efficient approach for glaucoma classification using morphometric 2- and 3-dimensional data derived from the Heidelberg Retina Tomograph, taking into account all given variables.

Case-Control Studies↗

PubMed2002

Discriminant analysis formulas of optic nerve head parameters measured by confocal scanning laser tomography.

PURPOSE: To evaluate whether discriminant analysis formulas of optic disc variables measured by confocal laser scanning tomography can detect glaucomatous visual field defects, to compare the diagnostic precision of these formulas to detect glaucomatous visual field defects in different types of chronic open-angle glaucoma, and to assess whether gender or refractive error influence the results obtained by the formulas. METHODS: One hundred and sixty-one patients with perimetrically defined glaucomatous optic nerve damage and 194 healthy subjects were recruited. All patients underwent confocal laser scanning tomography of the optic disc. The data were analyzed with three linear discriminant analysis formulas (sectorial, Bathija, and Mikelberg) obtained in sets of data different from those used in the present study. RESULTS: The areas under the receiver-operating characteristic curves of the three formulas and of the cup shape measure as a single parameter ranged from 0.649 to 0.81 in the entire group, and the results did not change when age-matched eyes were considered (0.618-0.812). In each of the glaucoma subgroups with primary open-angle, pseudoexfoliative, and normal-pressure glaucoma, and additionally in the hyperopic, myopic, female, and male subgroups, the sectorial formula had the highest diagnostic precision and the highest correlation coefficients with the visual field indices, followed by the Bathija and Mikelberg formulas, without major differences between the subgroups. All three formulas were more effective than the cup shape measure as a single parameter. CONCLUSION: In the various chronic open-angle glaucomas, the sectorial and Bathija formulas tended to have higher diagnostic precision than the Mikelberg formula and the cup shape measure. Gender and refractive error do not markedly influence the diagnostic precision of the formulas tested. The scores of the formulas are mild indicators of the amount of glaucomatous visual field loss. All three formulas are superior to the single cup shape measure in the detection of glaucomatous optic nerve damage.

Adult↗