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D Schweitzer

Publications and source records attributed to D Schweitzer.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Age-related maculopathy. Comparative studies of patients, their children and healthy controls].

BACKGROUND: The aim of this study was to evaluate prospectively whether there are differences in spectrometrically measurable parameters of the fundus between patients with early and late age-related maculopathy (ARM), the children of the ARM patients (F1 generation) and normals. METHOD: Using the "Jenaer Imaging Spectrometer", retinal oxygen saturation, xanthophyll, and intrinsic fluorescence were measured; the spatial distribution of xanthophyll was determined using the Rodenstock SLO 101 model. RESULTS: Xanthophyll is reduced in late ARM as compared to the F1 generation and the control group (alpha < 0.01). The different fluorescence spectra, measured at shortwave and at longwave excitation, suggest the presence of more than one fluorophore. Furthermore, the components of the fluorophores seem to be different between patients with ARM and their F1 generation. The longwave autofluorescence is age-dependent only in late ARM (r2 = 0.81). For the first time, we found an alteration in oxygen saturation in retinal vessels in patients with ARM. CONCLUSIONS: Xanthophyll is reduced only in late ARM. Autofluorescence and oxygen saturation are different between ARM patients, the F1 generation and normals, however, we were not able to identify a genetically based predisposition concerning the parameters studied.

Adult↗
PubMed2000

Survivor guilt, submissive behaviour and evolutionary theory: the down-side of winning in social comparison.

In prior research submissive behaviour has been studied in relation to social comparison. Evolutionary theory conceptualized submissive behaviour as a fear-based self-protective strategy when in a subordinate position. In this study we hypothesized that survivor guilt, the type of guilt associated with feeling better off than others, is also linked to submissive behaviour. The Interpersonal Guilt Questionnaire, the Submissive Behaviour Inventory, the Eysenck Personality Questionnaire-Revised and the Automatic Thoughts Questionnaire were administered to a sample of 199 college students. Submissive behaviour was found to be significantly correlated with survivor guilt. Introversion, used as an indirect measure of the fear of being put down, was also correlated with submissive behaviour. A principal components analysis found two components: the first was composed of high loadings of submissiveness, survivor guilt and omnipotent responsibility guilt; the second was composed of high loadings of submissiveness and introversion. This supports the hypothesis that there may be two motivational states related to submissive behaviour, the fear of harm to the self, as described in prior studies, and the fear of harm to another or guilt-based submissive behaviour. We propose that survivor guilt has been selected by evolution as a psychological mechanism supporting group living, and that it may be considered from the perspective of inclusive fitness, reciprocal altruism, and multilevel selection theory.

Adaptation, Psychological↗
PubMed1999

[Oxygen saturation of retinal vessels. Studies for measuring with polarized light].

UNLABELLED: The accuracy of the spectrometric measurement of the oxygen saturation in retinal vessels is limited by its signal-to-noise ratio. The aim of this study was to investigate the possibility of enhancement of the reflection signal by the use of polarized light. MATERIALS AND METHODS: The Jena ophthalmospectrometer was equipped with two polarizing filters: one in the illumination and the other in front of the detector. Reflection spectra of erythrocytes streaming through a cuvette in the focus of an artificial eye were recorded. The influence of the polarization on the reflection spectra was investigated by rotating the polarizer in front of the detector. Furthermore, the degree of polarization of the light reflected from retinal vessels in vivo was determined. RESULTS: The degree of polarization of the light reflected from the erythrocytes was 0.6-0.8, whereas the polarization of light reflected by a standard white reflectance target was virtually zero. CONCLUSION: Polarized light can be used for the reduction of error in retinal vessel oximetry.

Blood Flow Velocity↗
PubMed1999

Observations on labor epidural analgesia and operative delivery rates.

OBJECTIVE: Our purpose was to compare operative vaginal and abdominal delivery rates in a large population before and after on-demand labor epidural analgesia became available. STUDY DESIGN: We retrospectively compared patients who gave birth during a 20-month period immediately before the introduction of an on-demand labor epidural analgesia service with those who gave birth during a 20-month period after the epidural usage rate had reached a plateau at approximately 60%. Operative vaginal and cesarean delivery rates were stratified according to parity and history of prior cesarean delivery. RESULTS: A total of 4859 women gave birth during the study period when on-demand epidural analgesia was available, and 4778 women gave birth in the study period before the availability of on-demand epidural analgesia. Comparisons between the women with and those without on-demand availability of epidural analgesia demonstrated no statistically significant differences in the rate of spontaneous vaginal delivery (69.5% vs 68.3%), the overall cesarean delivery rate (19.0% vs 19.4%), the primary cesarean delivery rate (13.2% vs 13.4%), or the operative vaginal delivery rate (11.1% vs 11.9%) between the 2 periods. There were no statistically significant differences in mean gestational age at the time of delivery between the 2 groups, whereas there were statistically significant increases in the proportion of nulliparous women and in mean birth weight during the on-demand epidural period. Analysis after substratification of the study groups according to parity also revealed no statistically significant differences in the primary cesarean delivery rate or the proportion of women undergoing vaginal delivery. The sample size was adequate to exclude a 2% increase in the primary cesarean delivery rate between the 2 periods with 80% power. Subgroup analysis of the population of women who gave birth while epidural analgesia was available on request demonstrated that nulliparous parturient women who requested epidural analgesia were almost twice as likely to require operative vaginal or cesarean delivery as women who did not request epidural analgesia, a finding suggesting that women who request labor epidural analgesia have an inherent propensity toward operative delivery. CONCLUSION: The introduction of an on-demand labor epidural analgesia service does not increase the rate of cesarean delivery or operative vaginal delivery.

Adult↗
PubMed1999

In vivo measurement of the oxygen saturation of retinal vessels in healthy volunteers.

A new method for the spatially resolved measurement of the oxygen saturation of retinal vessels is described. Imaging spectrometry was used for both measurements of transmission and reflectance spectra of whole blood in cuvettes as well as for fundus reflectance spectra. A model was developed for the calculation of the oxygen saturation, valid in the wavelength range between 510 nm and 586 nm, in that the internal reflectance is constant and only the transmitted light depends on layer thickness and hematocrit. Altogether 265 measurements were performed in different number at 30 eyes. In each measurement, the oxygen saturation was simultaneously determined for 193 locations along a line of 1.5 mm at the fundus. The mean oxygen saturation in retinal arteries was (92.2 +/- 4.1)% and (57.9 +/- 9.9)% in retinal veins. The mean retinal arterio-venous difference of the oxygen saturation was (35.1 +/- 9.5)%. The venous oxygen saturation depended on distance from the optic disc. The measured mean of the arterio-venous difference of the oxygen saturation corresponded well to the value of the brain (34%). The utilization of oxygen in the temporal quadrants (inferior: 39.4 +/- 10.4%) is significantly (p = 0.05) higher than in the nasal quadrants (inferior: 31.3 +/- 6.7%).

Adolescent↗
PubMed1998

Spontaneous osteonecrosis of the knee. Treatment and evolution.

We performed a retrospective study on 21 patients affected by unilateral spontaneous osteonecrosis of the femoral condyle. Fifteen were women and 6 men. Their average age was 66.9 years. In ten cases the onset of pain was sudden, with a clear previous history of trauma in two of them. Gait pain, effusion, and joint locking were the most frequent clinical symptoms. At the time of diagnosis, 7 patients presented with grade I necrosis, 8 grade II, 1 grade III, and 5 grade IV, following Koshino's classification [11]. The average percentage of osteonecrosis was 36.8%. Six patients underwent conservative treatment with physical exercises and nonsteroidal anti-inflammatory drugs. We performed arthroscopy alone in 4 patients, arthroscopy and drilling in 8, valgus high tibial osteotomy in 2, and total knee arthroplasty in 1. The overall results after an average follow-up 41 months were excellent and good in 76.2% of the cases, fair in 14.3%, and poor in 9.5%. An associated medial meniscus tear was found in half of the patients who underwent surgery. In patients diagnosed with grade III and IV osteonecrosis, no increase in the percentage of necrosis was observed.

Aged↗
PubMed1998

Open reduction and internal fixation of acetabular fractures.

Between 1982 and 1995, 84 patients with displaced acetabular fractures underwent open reduction and internal fixation in our institution. The mean follow-up was 5.5 years with a minimum of 2 years. There were 33 simple and 51 complex fractures according to the classification of Judet and Letournels. Reduction after operation was anatomical in 49% of the patients, satisfactory in 24%, and unsatisfactory in 27%. Using Merle d'Aubigné's scale, the clinical results were excellent in 39% of the patients, good in 29%, fair in 8%, and poor in 24%. Factors of statistical significance associated with a poor clinical outcome were T-shaped fractures, unsatisfactory reduction (> 3 mm residual displacement), age > 40 years and development of avascular necrosis. Acetabular surgery is demanding, and a high rate of complications can be expected. Trauma centres should designate a group of surgeons who will consistently treat these fractures in order to obtain more experience and better results.

Acetabulum↗
PubMed1998

A data reduction scheme for improving the accuracy of oxygen saturation calculations from spectrometric in vivo measurements.

A developing tool in ophthalmological research and practice is the study of the oxygen saturation in retinal vessels because this measurement contains important diagnostic information about the metabolism at the human ocular fundus. Imaging spectrometry enables locally resolved measurements of the oxygen saturation simultaneously in arteries and veins. The vessel reflex, imaging errors of the detection system and the noise of the signal result in substantial uncertainties in the calculated data. We present a data processing method for the improvement of the primary information leading to a reduction of the uncertainties of the derived oxygen saturation.

Biometry↗
PubMed1998

Nonproliferative diabetic retinopathy-reflection spectra of the macula before and after laser photocoagulation.

This study examines the influence of diabetic and laser photocoagulation on the reflection spectra of the macula. In the investigation 43 patients with type II diabetes mellitus and 33 normals were included. It was shown that the optical density in diabetics is increased compared to normals. After laser photocoagulation the reflection spectra have changed, suggesting a decrease in optical density. It is proposed that the therapeutic effect of photocoagulation in diabetic retinopathy is related to an alteration in blood flow in the choroid.

Adult↗
PubMed1997

Influence of laser coagulation therapy on untreated fellow-eyes in severe nonproliferative diabetic retinopathy-spectrometric results.

PURPOSE: The aim was to examine the influence of laser treatment on untreated fellow-eyes. METHODS: The effectiveness of the laser photocoagulation was investigated in 24 patients with type II diabetes mellitus and severe nonproliferative diabetic retinopathy. Using a spectrometric technique, the measurements in the macula were performed one day before laser coagulation and on the day directly following laser treatment. Further investigations took place 14 days and 6 weeks later. RESULTS: One day after coagulation, the reflection of the untreated fellow-eyes was found to be significantly increased between 530 and 600 nm, compared to the same eyes before coagulation. However, 14 days and 6 weeks after laser treatment alterations in the untreated eyes were no longer detectable. CONCLUSION: The choroidal blood volume seems to be decreased not only in coagulated eyes, but also in untreated fellow-eyes, and, presumedly, the choroidal blood flow is improved. Considering the short duration of these effects, a therapeutic consequence is not supposed.

Adult↗
PubMed1996

Anterior cruciate ligament reconstruction with fresh-frozen patellar tendon allografts: sixty cases with 2 years' minimum follow-up.

A prospective study was performed on 101 patients who underwent an arthroscopic anterior cruciate ligament (ACL) reconstruction with fresh-frozen patellar tendon allograft (bone-patellar tendon-bone). We present the results of the first 60 patients with a minimum follow-up of 2 years. Thirty-four were men and 26 women with a mean age of 23. In 45 patients, a postoperative arthroscopy was performed, and tissue biopsies of the reconstructed ACL were obtained. Patients were evaluated according to the International Knee Documentation Committee evaluation form. After a mean follow-up of 47 months, the overall results were normal or nearly normal in 85%. Under postoperative arthroscopy, the macroscopic appearance of the implant was similar to that of a normal ligament. The ACL allograft was covered with a normal, well-vascularized synovium. There were no cases of infection, disease transmission or tissue rejection. We conclude that the use of fresh-frozen patellar tendon allografts is a good method of ACL reconstruction.

Activities of Daily Living↗
PubMed1996

Imaging spectrometry in ophthalmology--principle and applications in microcirculation and in investigation of pigments.

Imaging spectrometry is a new technique that permits simultaneous measurements of reflectance spectra at different locations along a line. Results are three-dimensional images, whose coordinates are location, wavelength, and reflectance. A conventional fundus camera is adapted to a spectrograph and an intensified charge coupled device (CCD) matrix detector system. The spectral resolution of this spectrometer is lower than 2 nm within a spectral range between 395 and 710 nm. The local resolution is lower than 23 microns along a line of 1.5 mm. From an imaging spectrum, the extinction spectrum of blood in vessels can be calculated. Also, in case of a noisy extinction spectrum of blood, its approximation by a model function results in calibration-free measurement of the oxygen saturation. Considering the radiation transport in single fundus layers, the local distribution of the concentration-thickness product of xanthophyll, melanin, and choroidal blood can be calculated.

Animals↗
PubMed1995

Traumatic lumbosacral dislocation in a 5-year-old boy with eight years follow-up.

STUDY DESIGN: The authors present an unusual case of pure traumatic bilateral lumbosacral dislocation in a 5-year-old boy, the conservative treatment carried out, and the long-term result. OBJECTIVES: To describe a rare traumatic lesion in children and evaluate the result obtained with conservative treatment. SUMMARY OF BACKGROUND DATA: Watson-Jones was the first to describe this type of lesion. Since then, only a few cases have been added. Most authors suggest that open reduction should be carried out. No cases of this type of injury in children have been reported. METHODS: A 5-year-old boy was hit in the lumbosacral region with a rocking chair. Examination showed neurologic deficit of left L5 and S1 nerve roots. Roentgenographic examination and computed tomography scan confirmed the anterior dislocation of the fifth lumbar vertebra on the sacrum without any fracture. He was treated with traction, followed by hyperextension in a Cotrel traction table and further immobilization with a lumbar plaster jacket. RESULTS: Eight years after the injury, the patient had no neurologic deficit and lumbar radiographs showed a good alignment of the lumbosacral spine. CONCLUSION: In children with traumatic lumbosacral dislocation, closed reduction should be attempted even if neurologic deficit is present.

Child, Preschool↗
PubMed1995

Optical properties of ocular fundus tissues--an in vitro study using the double-integrating-sphere technique and inverse Monte Carlo simulation.

Various models have been published calculating the light transport at the ocular fundus either for interpretation of in vivo reflectance measurements or for the prediction of photocoagulation effects. All these models took the absorption spectra of the pigments located at the ocular fundus, melanin, haemoglobin, xanthophyll, and the photoreceptor pigments, into account. However, light scattering inside the single fundus layers has not been investigated in detail and was, therefore, neglected in the calculations or only considered by very rough approximations. This paper presents measurements on specimens of retina, retinal pigment epithelium, choroid, and sclera using the double-integrating-sphere technique. Absorption coefficients, scattering coefficients, and anisotropy of scattering were calculated by an inverse Monte Carlo simulation from the measured collimated and diffuse transmittance and diffuse reflectance. Conclusions are drawn for the interpretation of fundus reflectance measurements, which are a useful tool in diagnostics and photocoagulation dosimetry.

Animals↗