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Biomedical subjects

K Rohrschneider

Publications and source records attributed to K Rohrschneider.

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

Stereotactic radiation therapy for malignant choroidal tumors: preliminary, short-term results.

PURPOSE: To evaluate the role of stereotactic radiation therapy (SRT) in the treatment of malignant choroidal tumors. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: Ten patients with unifocal choroidal metastasis (three lung carcinoma, three breast carcinoma, three colon carcinoma, one cutaneous melanoma) and five patients with primary choroidal melanoma underwent single-dose or fractionated SRT. METHODS: Before treatment, computed tomography (CT) scans of the orbit were obtained with the patient wearing an individualized immobilization mask. An integrated macro-CCD-camera system viewed the eye for detection of movements. Three-dimensional computer-based treatment planning was carried out. Dose distribution was calculated and displayed in isodose lines on the CT data set. For SRT, a dedicated stereotactic linear accelerator (6 MV) was used. Total doses for choroidal metastases were 12 to 20 Gy in a single dose or 30 Gy over 10 days (3 Gy each session), and total doses for choroidal melanoma were 50 Gy over 5 or 10 days (10 or 5 Gy each session). MAIN OUTCOME MEASURES: Best corrected visual acuity (ETDRS-chart), biomicroscopy, ultrasound examination, fluorescein angiography, and magnetic resonance imaging (MRI) were performed before treatment and at regular intervals after completion of SRT. RESULTS: During a follow-up period from 1 to 34 months (median, 6.5 months), local tumor control was achieved in all eyes. A decrease in tumor size on ultrasonography or MRI was noted in eight patients. No persistent side effects were observed during follow-up. CONCLUSIONS: Stereotactic radiation therapy allows steep dose gradients outside the target volume by minimizing the field of exposure. Thus only low radiation doses affect surrounding radiosensitive ocular structures. Our initial findings suggest that this technique may be effective in controlling tumor growth. Further studies are needed to compare treatment efficacy and safety with conventional treatment methods.

Adult↗
PubMed2000

Mutations in the VMD2 gene are associated with juvenile-onset vitelliform macular dystrophy (Best disease) and adult vitelliform macular dystrophy but not age-related macular degeneration.

Recently, the VMD2 gene has been identified as the causative gene in juvenile-onset vitelliform macular dystrophy (Best disease), a central retinopathy primarily characterised by an impaired function of the retinal pigment epithelium. In this study we have further characterised the spectrum of VMD2 mutations in a series of 41 unrelated Best disease patients. Furthermore we expanded our analysis to include 32 unrelated patients with adult vitelliform macular dystrophy (AVMD) and 200 patients with age-related macular degeneration (AMD). Both AVMD and AMD share some phenotypic features with Best disease such as abnormal subretinal accumulation of lipofuscin material, progressive geographic atrophy and choroidal neovascularisation, and may be the consequence of a common pathogenic mechanism. In total, we have identified 23 distinct disease-associated mutations in Best disease and four different mutations in AVMD. Two of the mutations found in the AVMD patients were also seen in Best disease suggesting a considerable overlap in the aetiology of these two disorders. There were no mutations found in the AMD group. In addition, four frequent intragenic polymorphisms did not reveal allelic association of the VMD2 locus with AMD. These data exclude a direct role of VMD2 in the predisposition to AMD.

Adolescent↗
PubMed2000

[Utilization of a new night vision enhancement device (DAVIS)].

PATIENTS AND METHODS: Following complete ophthalmologic examination 37 patients with night blindness due to Retinitis Pigmentosa (sometimes Usher-Syndrome) and Choroideremia (n = 3) performed several tests with DAVIS during darkness. We evaluated the improvement of visual function on a special outside course in the city of Heidelberg (duration 1.5 to 4 hours). RESULTS: Twenty six of the patients were able to better recognize obstacles, 28 could see objects which were not seen without DAVIS. Twenty two of the 37 patients would use the DAVIS. Patients needed a visual acuity of more than 0.1 and more than 6 degree of central visual field to experience improvement with DAVIS. However, in patients with only minimal changes of the visual field, the restriction due to the presence of the device was a drawback. Sudden occurrence of light sources leads to blinding and limits the indoor use. CONCLUSION: DAVIS enhances contrast acuity especially during night and twilight. This leads to improvement of orientation due to better recognition of obstacles and allows rehabilitation of patients with night blindness for outdoor mobility. Individual test and adjustment of DAVIS is necessary to allow exact and adequate prescription.

Adolescent↗
PubMed2000

[Painless orbital swelling after sojourn in tropics. Cysticercosis and other parasitic eye diseases].

BACKGROUND: The differential diagnosis of painless orbital swelling is complex and based on radiological and physical examination as well as laboratory tests. Due to increasing tourism to exotic countries a thorough history is important to observe diseases which are rare in industrialised countries but frequent in developing countries. PATIENT: A 30-year-old man complained about a painless orbital swelling in the absence of general symptoms. Orbital examination revealed a normal globe. MRI scan and B-scan ultrasounds showed an orbital cyst with a diameter of 1 cm. The patient's history disclosed lengthy travel to India as well as South East Asia. RESULTS: Histopathological examinations following excision of a whitish intraorbital mass showed a cream-white, thin walled cyst with a single central invaginated scolex with suckers and hooklets. This finding is characteristic for cysticercosis. CONCLUSIONS: Cysticercus cellulose is the larval stage of the pork tapeworm Taenia solium. It is transmitted by ingestion of contaminated food or water. Ocular affection is reported concerning the vitreous or subretinal localisation, less often in the anterior segment, subconjunctiva or orbita. Especially after trips to tropical regions, parasitic diseases should be kept in mind when dealing with unusual eye symptoms. Besides cysticercosis there are e.g. echinococcosis, onchocercosis (river blindness) and infections with toxocara or Loa loa.

Adult↗
PubMed1999

[Experimental external irradiation of corneal neovascularization].

UNLABELLED: The clinical effect of ionidizing radiation on ocular neovascularizations is controversial not only because of the variety of treatment modalities. The aim of our study was to investigate an experimental model which allows to evaluate radiation parameters and to study the mechanism of the inhibitory effect on neoangiogenesis. METHODS: Corneal angiogenesis was induced by use of a micropocket assay in NZW rabbits. Pellets with 500 ng bFGF in 2% methylecellulose were implanted into the stroma 2.0 mm from the limbus. Initiation of vessel growth occurred on day 3. At this time radiation was performed with different doses (single dose of 15 to 30 Gy or fractionated 5 x 5 Gy) using a 6 MeV linear accelerator. Vascular growth was quantified. RESULTS: Irradiation with a total dose of 25 Gy applied in a fractionated regimen or as single-dose irradiation on the day of surgery or on day 6 after surgery did not significantly reduce neovascular growth. In contrast, postoperative radiation therapy on day 3 was able to reduce the area of ingrowing vessels significantly (P < 0.01). In spite of the relatively high dose there were no significant side effects during the observation period of 8 weeks. CONCLUSION: Our results show that single-dose radiation (> or = 25 Gy) is sufficient to inhibit the growth of corneal neovascularizations. With this model it might be possible to investigate parameters for therapy of ocular neovascularizations as well as the underlying mechanisms.

Animals↗
PubMed1999

[Ophthalmological rehabilitation - experience at the University Eye Hospital Heidelberg].

BACKGROUND: The rehabilitation of low vision patients is of increasing importance since the number of these patients has grown rapidly. We wanted to evaluate the actual spectrum of patients concerning age and diagnoses and the appropriate low vision aids (LVA) in 1 year. METHODS: The records of the patients seen in our low-vision unit in 1996 were retrospectively evaluated. We correlated visual function, ophthalmological diagnoses and age to the magnification needed for rehabilitation and the use or prescribed LVAs. RESULTS: There was a nearly homogeneous distribution concerning age with a range from 0 to 99 years. Most patients presented with age-related macular degeneration (25.6 %) while 10 % each had retinitis pigmentosa and optic atrophy. Simple low vision aids such as high plus reading additions (29 %) and magnifiers (18.5 %) were prescribed in the majority of patients. However, closed-circuit TV (CCTV) systems were necessary in 25 %. CONCLUSIONS: Rehabilitation of low vision patients is often possible with simple LVAs. This is especially true for patients suffering from age-related macular degeneration. Since there is a tremendous-amount of different diseases, adequate diagnostic and individual counseling is of major importance.

Adolescent↗
PubMed1999

[Techniques for reconstruction of the corneal surface by transplantation of preserved human amniotic membrane].

Persistent defects of the ocular surface remain a therapeutic challenge, which often requires surgical intervention. Recently, transplantation of human amniotic membrane has been suggested for reconstruction of the corneal surface. We describe two techniques using cryo-preserved amniotic membrane. Transplantation of several layers of amniotic membrane can successfully restore deep corneal ulcers associated with persistent epithelial defects. When such defects are not associated with stromal ulcers, they might benefit from amniotic membrane grafts sutured to cover the entire corneal surface. Both methods may serve as valuable tools for ocular surface reconstruction, especially in the context of impaired epithelial function.

Amnion↗
PubMed1999

Multilayer amniotic membrane transplantation for reconstruction of deep corneal ulcers.

PURPOSE: To evaluate the efficacy of multilayer amniotic membrane transplantation for reconstruction of corneal epithelium and stroma in the context of deep corneal ulcers. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: Eleven consecutive patients with deep corneal ulcers refractory to conventional treatment; six patients had herpetic keratitis and five had other forms of neurotrophic keratitis. INTERVENTION: Multilayer amniotic membrane transplantation with kryopreserved human amniotic membrane. MAIN OUTCOME MEASURES: Integrity of corneal epithelium and stroma, opacification, and appearance of grafted membrane during 12 months follow-up. RESULTS: Amniotic membrane transplantation markedly reduced ocular inflammation in all patients. Epithelium healed above all corneal ulcers within 4 weeks and remained stable in 9 of 11 patients for 1 year. Two patients with recurrent epithelial defect suffered from severe neurotrophic keratitis. Following transplantation the amniotic membranes gradually dissolved over a period of 12 months, but stromal thickness remained stable. CONCLUSION: Amniotic membrane transplantation allows corneal surface reconstruction in patients with persistent epithelial defects. The multilayer technique is useful for treating deep corneal ulcers and even descemetoceles. Because the procedure results in stability of the ocular surface over a period of more than 12 months in most patients, it may be considered an alternative to conventional surgical techniques for ocular surface reconstruction.

Adult↗
PubMed1999

The 2588G-->C mutation in the ABCR gene is a mild frequent founder mutation in the Western European population and allows the classification of ABCR mutations in patients with Stargardt disease.

In 40 western European patients with Stargardt disease (STGD), we found 19 novel mutations in the retina-specific ATP-binding cassette transporter (ABCR) gene, illustrating STGD's high allelic heterogeneity. One mutation, 2588G-->C, identified in 15 (37.5%) patients, shows linkage disequilibrium with a rare polymorphism (2828G-->A) in exon 19, suggesting a founder effect. The guanine at position 2588 is part of the 3' splice site of exon 17. Analysis of the lymphoblastoid cell mRNA of two STGD patients with the 2588G-->C mutation shows that the resulting mutant ABCR proteins either lack Gly863 or contain the missense mutation Gly863Ala. We hypothesize that the 2588G-->C alteration is a mild mutation that causes STGD only in combination with a severe ABCR mutation. This is supported in that the accompanying ABCR mutations in at least five of eight STGD patients are null (severe) and that a combination of two mild mutations has not been observed among 68 STGD patients. The 2588G-->C mutation is present in 1 of every 35 western Europeans, a rate higher than that of the most frequent severe autosomal recessive mutation, the cystic fibrosis conductance regulator gene mutation DeltaPhe508. Given an STGD incidence of 1/10,000, homozygosity for the 2588G-->C mutation or compound heterozygosity for this and other mild ABCR mutations probably does not result in an STGD phenotype.

ATP-Binding Cassette Transporters↗
PubMed1998

[Image flicker frequency of television reading aids. Effect on reading comfort for visually handicapped patients].

PURPOSE: To compare reading speed and reading comfort between closed-circuit television systems (CCTVs) with different image refresh rates. METHODS: Reading speed was measured with three CCTVs that only differed in repeat frequency (50, 60 and 70 Hz) in 21 patients with age-related macular degeneration and 10 controls. We compared reading speed measured in syllables per minute of 16 different reading templates with about 500 syllables each. RESULTS: Reading speed was equal with all CCTVs. Eighteen of 21 patients identified and disliked 50 Hz CCTVs because the image quality was worse. An image quality of 70 HZ enabled patients to use positive contrast with the best reading speed. CONCLUSIONS: Although reading speed does not improve with increasing frequency, flickering of 50 Hz CCTVs is critical for low-vision patients. The preference of low-vision patients for negative contrast image is more likely due to flickering with a lower repeat rate and 70 Hz CCTVs may allow more comfortable reading in positive contrast.

Aged↗
PubMed1998

[Transplantation of amniotic membrane for reconstruction of the eye surface].

Persistent defects of the ocular surface remain a therapeutic challenge that often requires surgical intervention. Recently, the transplantation of human amniotic membrane has been added to our therapeutic armentarium. This thick basement membrane has distinct biological properties that influence cellular differentiation and proliferation. Amniotic membrane obtained from cesarean deliveries is prepared and cryopreserved under sterile conditions and can be sutured onto the ocular surface. This procedure allows for reepithelialization of persistent corneal ulcerations as well as filling of stromal defects. Amniotic membrane can successfully be employed for ocular surface reconstruction following large corneal excisions and in the context of limbal stem cell disease for pterygium surgery as well as for various kinds of reconstruction of the conjunctiva. Taken together, amniotic membrane transplantation can serve as a valuable tool for ocular surface reconstruction, especially in the context of impaired epithelial function.

Amnion↗
PubMed1998

[Familial juvenile macular dystrophy with congenital hypotrichosis capitis].

BACKGROUND: Our knowledge about the pathogenesis of hereditary macular diseases is still very circumscript. For genetic determination, a knowledge of the coincidence of eye symptoms and other defined common symptoms is helpful. The purpose of this paper was to present two sisters of a family of consanguineous parents with the combination of hypotrichosis of the head and macular dystrophy in the context of a tricho-ocular malformation of an ectodermal dysplasia. A review of the recent literature is included. PATIENTS AND METHODS: Two 13- and 17-year-old sisters presented at our hospital with reduced visual acuity because of symmetrical central changes of the retinal pigment epithelium and chorioatrophic scars according to macular dystrophy combined with hypotrichosis capitis. We performed fundus perimetry and histological examinations of the hair. RESULTS: The 13-year-old patient exhibited central changes of the retinal pigment epithelium leading to a relative central scotoma for Goldmann 1/4 during fundus perimetry in both eyes (visual acuity 0.125 and 0.4). We found central chorioatrophic scars, followed by absolute central scotomas, with unstable fixation in the upper retinal hemisphere in her 17-year-old sister with reduced visual acuity (0.16 and 0.2). CONCLUSION: There are few descriptions of the association of macular dystrophy and hypotrichosis. The combination of hypotrichosis and macular dystrophy could make genetical analysis easier. Mutational analysis of the TIMP-3 gene that has previously been associated with Sorsby fundus dystrophy did not reveal any disease-causing mutations in our patients.

Adolescent↗
PubMed1998

[Location of the fovea at the fundus in relation to the optic nerve head].

BACKGROUND: Exact determination of the location of the fovea may be difficult, especially in patients suffering from macular pathology. The purpose of this study was to evaluate whether the distance between the optic nerve head and fovea in healthy eyes may be helpful in such patients. PATIENTS AND METHODS: We measured the distance between the center of the optic nerve head and the fovea in 165 healthy eyes in a horizontal and vertical direction. Results were correlated to the refractive status. RESULTS: There was a relatively high deviation between all eyes for the distance between the optic disc and the fovea (15.5 +/- 1.2 degrees [12.8 to 21.3 degrees]). There was a significant relationship between this distance and the refraction (r = 0.353, P < 0.001). Intraindividual deviation between the right and left eyes showed a markedly lower variance (0.67 +/- 0.49 degree [0.05 to 2.3 degrees]). CONCLUSION: The distance between the optic nerve head and the fovea does not allow for meaningful determination of the location of the fovea in eyes in which morphological changes have occurred. However, knowledge of this distance from the other eye of the same patient is helpful.

Adult↗
PubMed1998

In vivo fluorescence microscopy of corneal neovascularization.

PURPOSE: The purpose of our study establish an animal model to study the microcirculation in corneal neovascularization in the living animal atraumatically. METHODS: Corneal neovascularization was induced in New Zealand white rabbits by a standard micropocket assay utilizing pellets with 250 ng basic fibroblast growth factor. Anesthesia consisted of intramuscular injections of ketamine and xylazine. Intravital microscopy was performed without preparation of the cornea. Rhodamine 6G was used as fluorescent dye to stain leukocytes. Fluorescein-isothiocyanate-dextran served as plasma marker. Microcirculation analysis was done off-line by digital video imaging with special analysis software and included the following parameters: vessel diameters, blood velocity, and differentiation of leukocytes according to their interaction with endothelium into free-floating. rolling and sticking leukocytes. RESULTS: Vessel diameters in venular trunk vessels showed diameters of 54.0 +/- 13.3 microns with 1.1 +/- 0.5 mm/s flow; 29.4 +/- 16.3% of all leukocytes were attached to the vascular wall. The number of sticking leukocytes was found to be 17.8 +/- 36.0 cells/mm endothelial surface. Values are given for arteriolar trunk and branch as well as venular branch vessels. CONCLUSIONS: This method for in vivo microscopic observation and quantification of the vasculature of the ocular surface seems to be suitable for evaluation of microhemodynamic and leukocyte measurements in mature neovascular vessels. It allows atraumatic experiments without corneal preparation procedures which disturb the microcirculation. The results concerning microhemodynamics and adherence of leukocytes are in a range comparable to other microcirculation studies. This new model could provide insight into the pathophysiology of microcirculatory disorders of the anterior eye segment, e.g. during angiogenesis.

Animals↗
PubMed1998

Thalidomide inhibits corneal angiogenesis induced by vascular endothelial growth factor.

BACKGROUND: Ocular diseases caused by neovascularization are among the leading causes of blindness. No specific pharmacological treatment is available. Among potential drugs, thalidomide deserves special interest since a wide body of clinical experience exists. However, its antiangiogenic effect is controversial. We therefore investigated the effect of thalidomide on corneal angiogenesis induced by vascular endothelial growth factor (VEGF), which has a special role among angiogenic growth factors. METHODS: Corneal neovascularization was induced in NZW rabbits by an intrastromal pellet loaded with 500 or 750 ng VEGF. Animals received two daily feedings of 200 mg/kg thalidomide. RESULTS: Significant inhibition of corneal angiogenesis (P < 0.0001) was caused by the teratogenic dose of thalidomide after the 5th day of treatment and persisted for more than 16 days. No obvious side effects were recorded. CONCLUSIONS: Thalidomide has a significant antiangiogenic effect against VEGF-induced neovasclar growth. Together with earlier findings this observation indicates that the drug inhibits two angiogenic pathways which are mediated through integrin adhesion molecules.

Administration, Oral↗
PubMed1998

Normal values for fundus perimetry with the scanning laser ophthalmoscope.

PURPOSE: To evaluate the normal light sensitivity values for fundus perimetry and their short time fluctuation (reliability) in normal volunteers of different ages. After the development of full-threshold static fundus perimetry, age-corrected sensitivity values for normal subjects are required to interpret results and to compare them with conventional computerized perimetry. METHOD: Full-threshold fundus perimetry of the central field (33 x 21 degrees) by means of the scanning laser ophthalmoscope was performed on 152 eyes of 99 healthy persons aged 16 to 77 years with normal vision and no eye disease. Fixation was simultaneously documented. Light sensitivity values were evaluated according to each subject's age and test point location. RESULTS: Linear regression analysis disclosed a significant (P < .0001) decrease of the mean sensitivity of 0.275 dB per decade of increasing age, starting with 16.6 dB at age 10 years. Standard deviation around the center of fixation was 0.287 degrees in the first decade, and it increased by 2.82 minutes of arc per decade (P < .0001). Variation in triple examinations of subjects did not differ from short time fluctuation. CONCLUSION: Visual fields examined with fundus perimetry show reliable measurements in a range comparable to conventional computerized perimetry. There is a significant correlation between increase of age and decrease of light sensitivity in fundus perimetry. Visual fields obtained with fundus perimetry seem to correlate well with known data from computerized static threshold perimetry. It should be recognized that even in normal subjects, the stability of fixation decreases with increasing age.

Adolescent↗
PubMed1998

Simultaneous confocal scanning laser fluorescein and indocyanine green angiography.

PURPOSE: To evaluate clinically a recently developed confocal scanning laser ophthalmoscope for simultaneous fluorescein and indocyanine green angiography. METHODS: After comprehensive ophthalmic examination, including stereoscopic biomicroscopy, and after color fundus photographs, simultaneous confocal scanning laser fluorescein and indocyanine green angiography was performed after injection of 500 mg of fluorescein and 25 mg of indocyanine green mixed in one syringe using the Heidelberg Retina Angiograph. An argon laser beam (488 nm) and a diode laser beam (795 nm) from an external source were delivered by single-mode fibers. Emission was recorded between 500 and 700 nm and above 810 nm, respectively. Digital images were displayed simultaneously on a monitor during angiography. RESULTS: Two hundred twenty simultaneous fluorescein and indocyanine green angiograms were obtained in 193 consecutive patients with various diagnoses, including exudative age-related macular degeneration with occult and classic choroidal neovascularization. Simultaneous angiography with both dyes gave high-contrast images during all phases of the angiography, which allowed for accurate correlation of fluorescein and indocyanine green angiographic findings and correct comparison of the transit of both dyes through the retinal and choroidal circulation. Corresponding display of quasisimultaneous frames facilitated interpretation of the angiograms. CONCLUSIONS: Confocal laser scanning angiography allows for quasisimultaneous fluorescein and indocyanine green angiography. The investigation is possible at low retinal irradiance and offers high-contrast digital images. Compared with consecutive angiographic investigations using both dyes, simultaneous angiography is less time consuming, requires only one injection, and, because quasisimultaneous frames are obtained, facilitates interpretation of the angiograms.

Adult↗