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Biomedical subjects

R Guthoff

Publications and source records attributed to R Guthoff.

At least 19 recordsLinked to original sources
PubMed1996

[Ultrasound biomicroscopy imaging of accommodative configuration changes in the presbyopic ciliary body].

Direct observation of the position of the ciliary body was possible only in cases of gross anatomic, and probably also functional, abnormalities. Utilizing the 50 MHz ultrasound biomicroscope, we investigated the profile changes of the ciliary body in ten eyes of ten patients, ranging in age from 54 to 86 years while they were ocusing on a target at a distance and afterwards on an object up close. After electronic image processing of ten single video pictures from each accommodative status, a summarized picture for every accommodative status was obtained. In seven of ten cases, during accommodation a remarkable shift of the ciliary body was observed anterior to the iris and in the direction of the lens equatore, while the iridociliary body contact zone became wider in five of the ten eyes. Ultrasound biomicroscopy allows visualization of the dynamics of the accommodative process. As the human ciliary body does not lose its contractility in the senium, the loss of accommodation in presbyopia is mainly caused by age-related changes of the lens and capsula.

Accommodation, Ocular↗
PubMed1995

Correlation of histological tumor vascularization and Doppler sonography in patients with malignant melanoma of the choroid.

BACKGROUND: In previous studies Doppler sonography was proven to the useful for diagnostics and follow-up of malignant melanomas of the choroid. METHODS: To evaluate the correlation between Doppler sonographical findings and the histological tumor vascularization, we examined five eyes of five patients with malignant melanoma of the choroid before enucleation with an ATL Ultramark-8 Duplex scanner and compared these results with computerized planimetry of histological tumor vascularization after immunohistochemical staining of vascular endothelium with anti-factor-VIII antibodies. RESULTS: We found no definite correlation of flow velocities with histological parameters of tumor vascularization. The tendency was for a decrease in maximum flow velocities as histological vascularization increased. CONCLUSIONS: Due to (1) the usual lack of sensitivity parameters of the used Duplex device for the clinical user and (2) the unpredictable branching pattern within a melanoma resulting in an unknown angle of incidence of the Doppler beam, we conclude that the quantitative results of Doppler sonography require cautious interpretation. Nevertheless, presence or absence of Doppler shifts is a valuable parameter for the follow-up of irradiated tumors.

Blood Flow Velocity↗
PubMed1995

[Computer program for improved diagnostic coding in ophthalmology based on the expanded ICD 10].

BACKGROUND: The coding of ophthalmological diagnoses is a long-standing problem that has recently been highlighted by the planned introduction of ICD 10. METHODS: Using an alphanumerical classification system for the first time, ICD 10 offers the space needed for necessary expansion without leading once again to dislocations in the numbering system. The FoxPro 2.5 database system was used to create a program based on an expanded ICD 10 that can be applied from DOS and Windows. RESULTS: ICD 10 was expanded by the addition of a numerical fifth digit, thus increasing the number of classifiable ophthalmological disorders by a factor of 4.2 from 390 to 1635. The new program greatly facilitates the handling of this substantial amount of data. CONCLUSIONS: The enhanced diagnosis coding achieved with the expanded ICD 10 permits nosologically exact statistics to be kept for use as a basis for further scientific work.

Data Display↗
PubMed1995

[Continuous ultrasound biomicroscopic imaging of accommodative changes in the human ciliary body].

BACKGROUND: Slitlamp observations of the position of the ciliary body behind the iris root are possible only in cases of gross anatomic, and probably also functional, abnormalities. This study was performed to investigate physiological changes of the human ciliary body configuration during accommodation. MATERIAL AND METHODS: We used the 50 MHz ultrasound biomicroscope to measure the ciliary body changes in 5 left eyes of normal subjects during accommodation, while the right eye, wearing corrective spectacles, focussed Snellen letters at a distance of 3 m. For desaccommodation plus lenses were utilized, while negative lenses were applied to blur vision as a stimulus for accommodation. During postprocessing the best images of the video sequence were recalled on a monitor and the profile of the ciliary body was manually drawn on a transparent folder. For interpretation we used a projection system with vector analysis. RESULTS: During accommodation there is a shift of the ciliary body anteriorly toward the scleral spur and in the direction of the lens equator. In 4 out of 5 eyes a contact between the ciliary body and the posterior iris surface could be demonstrated. There was a measurably widening of the anterior chamber angle in 3 out of 5 eyes. CONCLUSIONS: Ultrasoundbiomicroscopy seems to be a way for assessing ciliary body deformation during accommodation. Our results are in accordance with histologic and gonioscopic findings and confirm biomechanical theories of the accommodation process. Further investigations including online digital image processing will be necessary to evaluate accommodation in its complexity.

Accommodation, Ocular↗
PubMed1995

[Visualization of keratocytes in the human cornea with fluorescence microscopy].

There is little information about the state of human keratocytes in longterm cornea storage and the influence of these cells on the survival of the corneal transplant after keratoplasty. Up to now stromal keratocytes have not been taken into consideration in regard to the culture conditions in cornea banking. Therefore, a method was used, first described by Poole et al., who stained porcine corneas using the Live/Dead-Assay (Molecular Probes Inc.). After staining porcine and human corneal slices with the fluorogenic substance calcein AM and the fluorochrome ethidium homodimer, we examined the fluorescing cells to acquire more knowledge about the density, morphology and vitality of human keratocytes. Living cells are distinguished by the presence of ubiquitous intracellular esterase activity, determined by the enzymatic conversion of the virtually non-fluorescent cell-permeant calcein AM to the intensely fluorescent calcein, producing an intense, uniform, green fluorescence in living cells. Ethidium homodimer enters cells with damaged membranes and undergoes a 40-fold enhancement of fluorescence on binding nucleic acids, thereby producing a bright red fluorescence in dead cells. The examinations were performed using a conventional fluorescence microscope and a confocal slit scanning microscope. Like in the porcine corneas, we found three keratocyte subpopulations in the human corneas, but there were some differences in morphology and patterns of staining between the two species in the central and posterior stroma. After long periods of cornea storage we found signs of cell degeneration like loss of cytoplasmic processes and an increasing number of dead cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Binocular photometer for measuring light perception in diseases of the visual pathway].

In patients with a reduction in visual function because of optic nerve neuritis, light sensitivity is tested to detect differences between the right and left eye in combination with the swinging flashlight test and visual evoked potential (VEP). A binocular Zeiss microscope was modified to use integrated photometer-controlled binocular stimulus fields and a central light system for fixation and variation of the contrast (background illumination). For exact binocular measurements of light sensitivity on both eyes, electronically controlled test fields (visual angle 5 degrees-20 degrees) guarantees only macular or overfoveolar stimulation. In addition, splitting the light for each stimulus field from only one halogen lamp guarantees wave-length-independent testing. Patients with various retinal diseases and neuritis nervi optici pathology were examined using pattern VEP, testing of the absolute lower threshold of light sensitivity, and binocular comparison over the range of luminous density. This binocular optical photometer system allowed minimal differences to be identified in the present visual function and after the eye had recovered from optic nerve neuritis.

Evoked Potentials, Visual↗
PubMed1995

[Prevention of postenucleation syndrome: the hydroxylapatite silicone implant. Preliminary experimental studies and initial clinical experiences].

An orbital implant after enucleation compensates for volume deficiency and increases prosthesis motility. In the literature, however, an extrusion rate of orbital implant between 10 and 25% is reported. Since the introduction of hydroxylapatic ceramics (HAC), these numbers have been reduced considerably. The HAC, which is derived from corals, has a rough surface and requires a scleral covering for implantation. The HAC, which is made in the laboratory, can be produced with smoother surfaces, so that a homoplastic covering is no longer mandatory. A composite implant was developed to improve prosthesis motility further. This consists of artificial HAC at its anterior surface to guarantee safe tissue integration; the posterior part of the implant is manufactured from silicon rubber to create a jointlike structure in Tenon's capsule. Integration of the porous HAC in the orbital soft tissues has been tested and confirmed by animal experiments. After 30 full HAC implants and 25 composite implants, only one extrusion occurred. In all other cases, compatibility proved to be excellent; transmission of the motility to the prosthesis was moderate to good. Examinations comparing prosthesis motility and computer tomographically evaluated implant motility enabled the analysis of deficits in motility transmission of the implant for the artificial eye.

Animals↗
PubMed1995

[Ultrasound biomicroscopy for evaluation of space-occupying lesions of the anterior eye segment. Initial results].

Pavlin's group developed the ultrasound biomicroscope, and it has been in use since 1990. It is an ultrasound method working at high frequencies between 40 and 100 MHz. It is possible to resolve structures up to approximately 50 microns in size at a maximal depth of 5 mm. We examined about 80 patients with tumors in the anterior segments of the eye, mainly in the iris and the ciliary body. Good differentiation between cystic and solid space-occupying lesions is possible to say whether or not is malignant.

Adult↗
PubMed1995

Inflammatory pseudotumor of the anterior orbit. A symptom in allergic granulomatous angiitis (Churg-Strauss syndrome).

Allergic granulomatosis accompanied by angiitis (Churg-Strauss syndrome) constitutes an unusual disorder which is characterized clinically by bronchial asthma and hypereosinophilia, accompanied by systemic symptoms of histopathologically and by necrotizing vasculitis, extravascular granulomas and tissue infiltration by eosinophils. We report a case of a 4 year-old child presenting with acute pneumonia and deteriorated general condition. The biopsy of an inflammatory pseudotumor of the right anterior orbit revealed necrotizing vasculitis, extravascular epitheloid granuloma and eosinophilic tissue infiltration. These are characteristic changes of allergic granulomatous vasculitis (Churg-Strauss syndrome. Laboratory findings were characterized by blood eosinophilia, increased IgE value and the presence of antineutrophil cytoplasmic ant antibodies (p-ANCA). Local and systemic manifestations quickly regressed after parenteral application of corticosteroids. Two exacerbations of inflammatory pseudotumor occurred after reduction of the corticosteroid dosage. Systemic vasculitic syndromes are rare in childhood. Orbital manifestations in Churg-Strauss syndrome in childhood have never been reported.

Biopsy↗
PubMed1994

[Clinical decision aids using ultrasound biomicroscopy].

Ultrasound biomicroscopy (UBM) allows high-resolution imaging of the anterior segment due to ultrasound transducers between 50 and 100 MHz. At present stage of experience, mainly analysis of iris and ciliary body structures seem to be clinically rewarding. This is demonstrated by two similar looking tumors, involving the chamber angle. By means of UBM it was possible to differentiate between cystic and solid growths and to assess tumor extensions.

Adult↗
PubMed1994

Possible effects of radiobiological parameters on metastatic spread of uveal melanomas treated with 106Ru plaques.

We reviewed 184 cases of uveal melanoma treated with 106Ru eye plaques. The influences of the dose rate, the total dose and the initial tumour size on the incidence of metastases were of major interest in this retrospective analysis. It is widely accepted that the risk of metastatic spread increases with increasing tumour volume. However, for tumours measuring < 10 mm in basal diameter the dose rate in brachytherapy with 106Ru eye plaques might be important, since we observed a better prognosis for patients treated with plaques of relatively low activity.

Adult↗
PubMed1993

Radiotherapy of the R1H-tumor: dose-rate effect on tumor response in brachytherapy with 106-ruthenium eye applicators.

PURPOSE: The influence of the dose-rate on tumor response in radiotherapy with 106-Ruthenium eye plaques has been investigated in an experimental tumor system. MATERIALS AND METHODS: The identical total dose was applied within three different overall treatment times (42 hr, 192 hr and 312 hr), corresponding to dose-rates of 6.0 Gy/hr, 1.3 Gy/hr and 0.8 Gy/hr. RESULTS: The therapeutic outcome of brachytherapy varied significantly between the three groups of animals treated with different dose-rates. At a dose-rate of 1.3 Gy/hr all tumors were locally controlled, but no local control was observed when a dose-rate of 6.0 Gy/hr was delivered. 0.8 Gy/hr was less effective than 1.3 Gy/hr but more effective than 6.0 Gy/hr. CONCLUSION: These results were unexpected but they might be explained by an incomplete reoxygenation if the overall treatment time is too short (42 hr, dose-rate 6.0 Gy/hr) and by proliferation of tumor cells under treatment if the overall treatment time is too long (312 hr, 0.8 Gy/hr).

Animals↗
PubMed1993

Rates of local control, metastasis, and overall survival in patients with posterior uveal melanomas treated with ruthenium-106 plaques.

The prognostic importance of clinically assessed tumor variables, patient variables, and treatment variables of 184 patients treated with ruthenium-106 eye plaques for uveal melanoma was studied using crude survival, metastatic disease and local tumor control as the endpoints. Using the multivariate Cox proportional hazards model, tumor diameter, age and sex were identified as the strongest variables predicting survival. Risk of metastasis was found to be dependent on tumor size (diameter) only and the metastasis was generally observed within 6 years after the end of treatment (96%). Clinically diagnosed local tumor control was predicted by tumor T-stage, treatment time, and total dose to the sclera. No correlation between metastatic disease and local failure was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

[Resorbable implant materials in retinal detachment surgery. Initial animal experiment studies].

In detachment surgery after a mechanically stabile chorioretinal scar is at present full scleral indentation no longer mandatory. Following these considerations absorbable scleral implants have been developed and tested in an animal model. Cylindrical pieces of absorbable composite-material with a diameter of 5 mm were sutured as radial scleral explants in 18 rabbits. The composite material consisted of a polyglactin-polydioxanon ratio 7:1. The absorption time for polyglactin is 60 days, for polydioxanon 180 days. The explants produced initially in ultrasonographically measured buckle height between 3.2 and 4.0 mm. The clinical and ultrasonographical follow up study demonstrated a continuous decrease of buckle height. Two weeks after implantation there was a medium height of 2.0 mm after five weeks a medium elevation of 0.5 mm was found. Histopathological examinations showed incidence of a slight resorptive inflammation in the area of the buckle which was not evident after 12 weeks. No scleral infiltration or scleral thinning was found. The promising results have justified controlled clinical trials with the absorbable material which might allow to combine the advantages of silicone sponge explants (precise localization) with those of scleral buckles by inflatible balloons (reversibility).

Absorption↗
PubMed1993

Neurofibromatosis 2 in the pediatric age group.

Bilateral acoustic neurofibromatosis or neurofibromatosis 2 (NF2) is an autosomal dominant disease predisposing to the formation of multiple tumors in the central and peripheral nervous system. Vestibular schwannomas (VSs) are considered to be the hallmark of the disease, but other tumors and ocular findings occur as well. In patients that do not carry the NF2 mutation, VSs usually occur in the fifth or sixth decade of life. VSs in patients with NF2 are often bilateral and become symptomatic in the third or fourth decade of life. In order to define the early manifestations of NF2, we examined nine children who either had one parent with NF2 or had multiple skin or spinal tumors suggestive of NF2. In addition to neurological, dermatological, and ocular examinations, all patients were studied by gadolinium-enhanced magnetic resonance imaging of the brain and spine. None of the children exhibited symptoms or signs due to VSs. However, VSs were detected during the neuroradiological work-up in six children. Seven children developed symptoms or signs due to skin or spinal tumors. Slit lamp examination detected cataracts in four patients as young as 10 years of age. The diagnosis of NF2 in the pediatric age group requires a high degree of suspicion and should be considered in children with multiple central nervous system or skin tumors without cafe-au-lait spots or Lisch nodules. Because VSs are unlikely to produce the signs seen at the time of admission, careful examination of the skin and eyes is necessary and should be followed by gadolinium-enhanced magnetic resonance imaging of the brain and spine. First-degree relatives need to be examined as well.

Adolescent↗
PubMed1993

[Ophthalmologic differentiation of various forms of neurofibromatosis].

Neurofibromatosis (NF) is one of the most frequent autosomal-dominant hereditary disorders. The molecular-genetic differentiation of NF 1 and NF 2 has important implications for the ophthalmologist. Among 80 patients with NF 1, Lisch nodules were diagnosed in 83% as typical criteria for the disease. In 6 patients who did not meet the NIH criteria for NF 1 and NF 2, the ophthalmological investigation showed no cataracts or Lisch nodules; thus, the ophthalmological examination can help to confirm a subtype of NF. In 8 out of 22 NF 2 patients a juvenile posterior subcapsular cataract was diagnosed. Our examination demonstrates that the diagnostic value of lens opacities in NF 2 patients--especially for early detection of the disease--must be clarified, especially with regard to the fact that there were no patients with incipient cataract and no neuroradiological criteria for the disease.

Adolescent↗
PubMed1992

[Meningioma of the optic nerve sheath. Diagnostic problems despite use of modern imaging procedures].

In spite of modern optical examination techniques such as sonography, nuclear magnetic resonance tomography (NMR) and x-ray computer tomography up to now the meningioma of the optic nerve sheath still poses a problem in respect of differential diagnosis. This problem is illustrated by two case reports. In both patients a meningioma of the optic nerve sheath could be diagnosed only after various attempts using all the imaging techniques mentioned above. NMR in combination with Gadolinium injection gave most important information.

Cranial Nerve Neoplasms↗