PubMed Health⌕ Search

Biomedical subjects

K Heimann

Publications and source records attributed to K Heimann.

At least 19 recordsLinked to original sources
PubMed1995

CD95 (Fas/APO-1) antibody-mediated apoptosis of human retinal pigment epithelial cells.

CD95 (Fas/APO-1) is a cytokine receptor protein that signals apoptosis. Here we report that human retinal pigment epithelial cells express CD95 but are rather resistant to agonistic CD95 antibodies. Resistance to CD95 antibodies is overcome by preexposure to the cytokines, tumor necrosis factor-alpha or interferon-gamma, or by coexposure to CD95 antibodies and inhibitors of RNA or protein synthesis. The cells are resistant to tumor necrosis factor-alpha even in the presence of cycloheximide and only moderately sensitized to tumor necrosis factor-alpha-mediated toxicity by coexposure to actinomycin D. CD95-mediated apoptosis is inhibited by dexamethasone both after cytokine sensitization and upon coexposure to CD95 antibodies and actinomycin D or cycloheximide. Induction of apoptosis via CD95 may be involved in the regulation of retinal pigment epithelial proliferation at the vitreoretinal interface.

Antigens, Surface↗
PubMed1995

[Intraocular silicone lenses and silicone oil].

BACKGROUND: Foldable silicone intraocular implants are becoming more popular in conjunction with small incision phacoemulsification. PATIENTS: We observed three patients with silicone oil droplets adherent to the posterior surface of the silicone implant, following silicone oil removal after preceding vitreoretinal surgery with the installation of silicone oil. These droplets could not be dislodged intraoperatively either with focal aspiration or irrigation. They interfered with the patients subjective visual acuity. For this reason, we performed an exchange of the silicone intraocular implant against a PMMA one-piece lens in all three cases. RESULTS: This procedure resulted in an increase of the visual acuity. The mechanism of adherence between the two silicone polymers is finally not known. CONCLUSIONS: With increased use of implantable silicone intraocular lens and silicone oil this complication may be encountered more frequently. Therefore, implantation of silicone lens in vitreoretinal high risk eyes should avoided.

Aged↗
PubMed1995

[Idiopathic macular foramen: new aspects of staging and possible therapeutic concepts].

Idiopathic macular hole and its early stages raises one of the most fascinating subjects in retinal disease. In this review, we aim to summarize the current knowledge of pathogenesis, the recent classification and the strategies for therapy. Recent evidence strongly suggests tangential traction induced by a thin epiretinal membrane to be the main cause for idiopathic senile macular holes. A thickening of the epicortical vitreous membrane or the internal limiting membrane of the retina could be demonstrated in these cases. When such a precursor situation (stage I) is present, in many cases there will be a progression to a full thickness macular hole (stage II). Further traction usually causes an enlarging of the defect in these eyes and the classic appearance of macular holes (stage III-IV) can then be observed. The clinical appearance, the diagnosis and the strategies of treatment are discussed for all stages of idiopathic senile macular holes. Based on the deeper insight into macular hole development, prophylactic vitrectomy and removal of the epiretinal membrane in cases of stage I macular holes, has been considered in order to prevent a further progression of the disease. There is also evidence that in stages II-IV macular holes, a closure of the hole and a visual improvement can be gained by vitrectomy, removal of the epiretinal membrane and fluid-gas exchange. The additional application of biological modifiers (transforming growth factor-beta, human autologous serum or tissue glue) may enhance the adhesion of the detached retina and therefore lead to better anatomical and functional success rates. The results of the pilot studies are reviewed and the surgical techniques as well as the possible complications are discussed.

Blood Proteins↗
PubMed1995

Onset and recurrence of proliferative vitreoretinopathy in various vitreoretinal disease.

AIMS: This study aimed to evaluate both the mean time intervals between retinal disease and the development of proliferative vitreoretinopathy (PVR) and the time intervals at which recurrent PVR develops following various kinds of vitreoretinal disease and surgery. METHODS: One hundred and thirty six consecutive cases of PVR that were seen and operated on between 1991 and 1994 were evaluated retrospectively. Intervals between onset of disease and PVR or recurrent PVR were noted. Conditions leading to PVR, surgical procedures, and the final anatomical and functional results were evaluated. RESULTS: Before PVR was noted for the first time, an average of 1.06 vitreoretinal surgical procedures were performed (range 0 to 3). A mean of 1.99 surgeries were performed to control PVR or to reach an end stage where further surgery would have been unreasonable (range 0 to 5). The average (median) time interval between the onset of the retinal disease and PVR was 2.0 months (range 0.5 to 45 months). The median time intervals between surgery and recurrence for the second, third, or fourth times was also 2.0 months (range 0.5 to 34 months). CONCLUSIONS: PVR starts earliest at 2 weeks after an event and subsequently quietens down within a maximum of 45 months after treatment (median 2 months). PVR may recur more than once but the time course of the disease is likely to be the same for each recurrence.

Adolescent↗
PubMed1995

Intercellular adhesion molecule-1 levels in plasma and vitreous from patients with vitreoretinal disorders.

Intercellular adhesion molecule 1 (ICAM-1) is a member of the immunoglobulin superfamily with important functions in immune activation and inflammation. Its interaction with different cytokines [interleukin 1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma)] is important for lymphocyte migration into inflammatory sites. We used a sandwich enzyme immunoassay (EIA) for the quantitative determination of soluble ICAM-1 (cICAM-1) in vitreous and plasma from patients undergoing vitrectomy for a variety of proliferative vitreoretinal disorders. The values obtained were compared with the total vitreal protein. The respective concentrations of cICAM-1 in vitreous were as follows control samples, 3.47 +/- 1.84 ng/ml; proliferative diabetic retinopathy (PDR) of diabetes type I 27.43 +/- 14.72 ng/ml; PDR of diabetes type II, 32.46 +/- 10.31 ng/ml; idiopathic proliferative vitreoretinopathy 35.74 +/- 15.30 ng/ml; and traumatic PVR, 45.23 +/- 24.24 ng/ml. Plasma samples yielded the following concentrations: controls, 415 +/- 43.4 ng/ml; PDR of diabetes type I, 469 +/- 96.9 ng/ml; PDR of diabetes type II, 425 +/- 65.4 ng/ml; idiopathic PVR, 402 +/- 119.9 ng/ml; and traumatic PVR, 434 +/- 118.6 ng/ml. Our results demonstrate high levels of ICAM-1 in most proliferative vitreoretinal disorders. In PDR and in traumatic PVR, cICAM-1 levels were elevated significantly more than were total vitreal protein levels. In traumatic PVR, patients with a short interval between previous surgery or traumatic event demonstrated the highest levels of cICAM. Since plasma levels were not significantly altered, we suggest that local cICAM-1 production, possibly from macrophages, may be of importance in the early phase of PVR and PDR by enhancing immune activation and inflammation.

Diabetes Mellitus, Type 1↗
PubMed1995

Posterior drainage of intraocular fluid: an experimental approach on bovine cadaver eyes.

We evaluated the posterior drainage of saline in cadaver bovine eyes using different experimental procedures. The saline perfusion via a pars plana infusion into the vitreous cavity was measured in the following 5 different groups of 20 enucleated bovine eyes: 1, control; 2, vitrectomy; 3, vitrectomy + retinectomy; 4, vitrectomy + retinectomy + removal of retinal pigment epithelium (RPE); and 5, vitrectomy + retinectomy + removal of RPE + choroidectomy. The mean values obtained for the facility of saline outflow were as follows group 1, 0.0458 microliter min-1 mmHg-1; group 2, 0.0393 microliter min-1; group 3, 0.1308 microliter min-1 mmHg-1; group 4, 0.2288 microliter min-1; and group 5, 0.9985 microliter/min-1 mmHg-1. The retina appeared to be the major barrier to fluid movement from the vitreous to the chorioid, perhaps due to the lack of extracellular space and to the tight and impervious structure of the retina. The barrier function of the retina may explain the hypotony seen after rhegmatogenous retinal detachment and the decrease in intraocular pressure observed after the removal of silicone oil in eyes that had undergone retinectomy. Our results suggest that the reduction in intraocular pressure occurring after retinectomy is attributable to the new drainage pathway.

Animals↗
PubMed1994

The significance of vitronectin in proliferative diabetic retinopathy.

Vitronectin, an integrin-binding a-1-glycoprotein with potent cell-adhesion and proliferation-mediating properties, has been shown to be incorporated in surgically removed membranes from patients with proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR) and macular pucker. Therefore we developed an ELISA technique to quantify levels of vitronectin in human vitreous and plasma samples in order to be able to evaluate the significance of vitronectin in these different vitreoretinal diseases. Our results indicate a significant increase of vitronectin in all proliferative disorders except idiopathic macular pucker. Adjustment of all probes to equal total protein content yielded a significant increase only in PDR (type II diabetes). Plasma samples demonstrated a significant increase of vitronectin in patients with type II diabetes suffering from PDR. Therefore, break-down of the blood-retina barrier appears to be the most likely explanation for the increased levels of vitronectin in the vitreous. Our results indicate that vitronectin may not only be involved in the regulation of epiretinal membrane formation at significantly higher levels in patients with type II diabetes, but the increase of vitronectin in diabetic plasma may also help to explain the pathological alteration of the coagulation cascade in diabetics.

Blotting, Western↗
PubMed1994

Visual outcome of secondary lens implantation after trauma or complicated retinal detachment surgery.

PURPOSE: Visual outcome of intraocular lens (IOL) implantation as a separate surgical procedure after severe trauma of the anterior or posterior segment or after vitreoretinal surgery for complicated retinal detachment resulting in aphakia was evaluated. METHODS: The charts of all patients undergoing secondary IOL implantation for the above reasons between 1988 and 1992 were retrospectively reviewed. A special transcleral suturing technique was developed for the posterior chamber lenses, where needles are primarily passed from the outside through the sclera to enhance correct positioning of the sutures. RESULTS: In all but one of the cases in group 1, visual acuity after surgery was equal to or better than before surgery. In the second group, visual acuity after surgery was equal to or better than before surgery in 9 of 12 cases. CONCLUSIONS: Secondary IOL implantation after severe trauma or vitreoretinal surgery for complicated retinal detachment is a fairly safe technique, with only few transient complications. Visual acuity did not deteriorate after surgery by more than two lines in any the cases discussed. Peripheral binocularity was restored in all cases. The suturing technique described here, in which the needles are primarily passed from the outside through the sclera, offers the advantage of exact positioning of the haptics in the ciliary sulcus.

Adolescent↗
PubMed1994

Histopathologic study of epiretinal proliferations after vitrectomy with daunomycin and silicone oil.

PURPOSE: The cellular composition of primary and recurrent periretinal proliferations has been widely described. The use of daunomycin, an antiproliferative antibiotic, has been recommended to reduce these proliferations. Two recurrent membranes after intraoperative application of daunomycin were examined. METHODS: Two epiretinal membranes, which were removed 5 months and 20 months after vitrectomy with daunomycin, were examined by light and electron microscopy to determine the structure and cellular composition of these membranes. RESULTS: The matrix of the membranes consisted of new collagen with fiber diameters between 20 and 22 nm. Fibrocytes and macrophages were present in both specimens. Retinal pigment epithelial cells and fibrous astrocytes were present in only one specimen. CONCLUSION: Retinal pigment epithelial cells, which are consistently present in primary periretinal membranes, were found in only one of the two specimens examined. Myofibroblasts, also normally present, were not found. The other cells found are typically seen in primary periretinal proliferations.

Adult↗
PubMed1994

[Protein composition of the vitreous body in proliferative diabetic retinopathy. An analysis with 2-D-electrophoresis].

Gradient SDS-polyacrylamide gel electrophoresis is a useful technique for characterization of soluble human vitreous protein. However, this technique is limited in the case of suboptimal discrimination power. In this study, we used 2-D electrophoresis to analyse the protein composition of proliferative diabetic retinopathy (PDR) intraocular fluid (n = 10), and compared it with normal vitreous (n = 10) and serum (n = 10). In normal vitreous, the protein content consisted mainly of albumin, transferrin, alpha 1-antitrypsin, IgG, and prealbumin as confirmed by the comparison with protein standards. Compared to vitreous controls, all PDR samples were shown to have lower amounts of transferrin, alpha 1-antitrypsin, and prealbumin. However, the amounts of IgG were higher than in the controls. This reflects a shift to a serum-like protein profile, indicating a blood-retinal barrier breakdown. However, we also detected in PDR vitreous three protein spots in a low-molecular-weight range (5-10 kDa) none of which could be found in native vitreous or in serum. Therefore, additional local protein synthesis appears to be present in the pathogenesis of PDR. 2-D electrophoresis permits precise characterization of the soluble vitreous proteins which may be associated with the fibrovascular proliferative vitreoretinal response.

Blood Proteins↗
PubMed1994

Validity of two-dimensional data obtained with the Heidelberg Retina Tomograph as verified by direct measurements in normal optic nerve heads.

The Heidelberg Retina Tomograph (HRT) was recently developed to measure two- and three-dimensional parameters of the optic disc. The instrument gives measurement results on an absolute scale; the validity of the scaling has never been proven in the living eye. Eight phakic eyes (eight patients) scheduled for subsequent pars plana vitrectomy were selected for this study. The optic disc was scanned using the HRT. During vitrectomy, the disc was measured directly using a modified retina spatula that had a 2.5-mm scale with a grading of 1/10 mm at the tip. The measurement was recorded with a high-resolution video system adapted to a Zeiss operation microscope. We used a vitrectomy contact lens with a flat surface. First we looked for reference points along the disc margin that could be clearly identified on both images, then we determined the distances between these points. Calculations from HRT data followed according to the software used in this instrument. Calculations from video images were related to the grading of the intraocular scale instrument. As determined using HRT software version 1.08, the mean ratio of HRT distances obtained by direct video measurements was 1.031 (SD, +/- 0.099; SE, +/- 0.035). No significant correlation between the ratio and the ametropia of the eyes could be verified (r = 0.506, P = 0.20). On average, the two-dimensional measurements of the HRT were correct. Furthermore, we used software version 1.07, which does not correct the image size depending on refraction, and found that the mean ratio of HRT distances obtained direct video measurements was 0.985 (SD, +/- 0.108; SE, +/- 0.038).(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1994

Atypical presentations of Best's vitelliform macular degeneration: clinical findings in seven cases.

The clinical findings obtained in seven patients from four families with atypical vitelliform macular degeneration are described. Five patients had an onset of the disease in childhood and two patients, at the age of 45 years. Their visual acuity was mildly reduced (0.52 +/- 0.27). The fundus showed variable changes with single or multiple central or paracentral yellowish subretinal exudates and deposits, sometimes surrounded by scars. Both eyes were affected in all patients. The scotopic and photopic electroretinograms were normal in all cases. The electrooculogram (EOG) showed a significant reduction of the light rise in all affected eyes, and in five eyes a reduction in the dark trough could be observed. In three clinically unaffected first-order relatives with normal fundus appearance, the light rise of the EOG was reduced, thus identifying them as gene carriers. The clinical features of atypical vitelliform macular degeneration are discussed with respect to similar diseases that must be excluded and may give reason for misdiagnosis.

Child↗
PubMed1993

Tenascin and decorin in epiretinal membranes of proliferative vitreoretinopathy and proliferative diabetic retinopathy.

Extracellular matrix (ECM) synthesis plays an important part in the pathogenesis of the intravitreal membranes and is thus characteristic of both proliferative vitreoretinopathy (PVR) and the involutive stages of proliferative diabetic retinopathy (PDR). Using a polyclonal antiserum against human decorin and a monoclonal antibody against human tenascin, we detected these molecules in membranes from patients with raumatic PVR (n = 10), idiopathic PVR (n = 8), and proliferative diabetic retinopathy (n = 8). We conclude that both tenascin and decorin play a role in the development of epiretinal PVR and PDR membranes by controlling cell adhesion and regulating ECM formation.

Antibodies, Monoclonal↗
PubMed1992

Retinal detachment in eyes with congenital glaucoma.

Five patients with congenital glaucoma were treated for complicated retinal detachment. All patients underwent a pars plana vitrectomy and fluid/gas or fluid/silicone exchange. The technical difficulties of operating on buphthalmic eyes are described. Due to subretinal reproliferation, corneal decompensation, and pressure elevation, the functional prognosis is still poor.

Adult↗
PubMed1992

Artificial iris diaphragm and silicone oil surgery.

In order to avoid contact between silicone oil and the cornea and subsequent painful corneal dystrophy in aniridial eyes, an artificial iris diaphragm was constructed. It consists of polymethylacrylat (PMMA) and simulates the situation of the iris with a central pupillary opening and inferior iridectomy. To date, these diaphragms have been implanted in 11 cases of the severest ocular trauma with accompanying aniridia and proliferative vitreoretinopathy. In the presence of sufficient residual secretion of the ciliary body (9 cases), the diaphragm assumes the function of normal iris and prevents the silicone oil from coming into contact with the corneal endothelium. The transparent diaphragm ensures a view through to the fundus. In the early postoperative period, there was, as anticipated, a fibrinous reaction in the area of the anterior segment.

Adult↗