Biomedical subjects

H P Heidenkummer

Publications and source records attributed to H P Heidenkummer.

At least 19 recordsLinked to original sources

PubMed1998

Ultrastructure of epiretinal membranes associated with macular holes.

BACKGROUND: The role of tangential traction exerted by epiretinal membranes in the pathogenesis of macular holes is not fully understood. Furthermore, the role of glial cells in the formation and/or closure of macular holes remains to be elucidated. METHODS: To better understand the pathogenesis of macular hole formation and to compare the ultrastructural features of epiretinal membranes associated with macular holes of primary and secondary etiology, we harvested 23 translucent epiretinal membranes associated with macular holes stages III-IV at the time of pars plana vitrectomy and examined them electron microscopically. Eighteen membranes were obtained from patients with idiopathic macular holes. 3 membranes from patients with myopic macular holes and 2 epiretinal membranes were associated with macular holes which had developed after retinal detachment surgery. RESULTS: Eighteen membranes contained a continuous undulating piece of inner limiting lamina (ILL). Sixteen of 18 epiretinal membranes at the margins of idiopathic macular holes, 2 of 3 membranes in myopic macular holes and both membranes associated with a macular hole after retinal detachment surgery demonstrated mono- or multilayers of fibrous astrocytes with single macrophage- or fibrocyte-like cells. Vitreous and newly formed collagen occupied the space between the ILL and the glial cells. Three macular holes were surrounded by rather firmly attached acellular ILL. CONCLUSIONS: Glial cells and newly formed collagen may play an important role in macular hole formation by exerting tangential traction regardless of the underlying disease process. Glial cells, however, may also be involved in healing of the retinal defect and pars plana vitrectomy with peeling of an epiretinal membrane, and/or the ILL may induce directed glial cell proliferation and migration. The similar ultrastructure of epiretinal membranes associated with macular holes and "simple epiretinal membranes" as described by Foos [8] suggests a common pathogenesis for macular holes and macular pucker.

Adult↗

PubMed1996

[Morphologic analysis of epiretinal membranes in surgically treated idiopathic macular foramina. Results of light and electron microscopy].

Anteroposterior and tangential traction on the central retina is an important factor in the pathogenesis of idiopathic macular hole formation. Histological studies have shown that macular holes of different stages can be associated with epiretinal membranes. Such membranes can be removed during surgery for macular holes. We investigated such tissue samples of 11 patients with macular holes in stages II-IV. Light microscopically, the tissue consisted of a thin collagen layer mostly covered by a thin layer of cells. Ultrastructural analysis revealed glial cells and macrophages as cellular components. The collagen can be ascribed to vitreous, inner limiting membrane and newly formed collagen. According to the morphological findings a multilayered tissue structure can be assumed. Macrophages were found on the retinal side of the inner limiting membrane and at the vitreal side of the tissue. Therefore, the macrophages probably originate from the retina as well as from the vitreous as so-called resident hyalocytes. Glial cells covered the inner limiting membrane forming pericellular collagen to which outer vitreous collagen fibrils can be attached. The multilayered membrane structure might possibly be the cause for only partial laminar surgical extraction so that contractile or potentially proliferative tissue residues might be one of the reasons for surgical failures after incomplete membrane peeling.

Aged↗

PubMed1996

[Recurrent vitreoretinal membranes in intravitreal silicon oil tamponade. Morphologic and immunohistochemical studies].

During intraocular silicon oil tamponade, recurrent vitreoretinal membranes can become clinically relevant and may need surgical excision. We investigated 40 PVR and 10 diabetic membranes which had formed during intraocular tamponade with highly purified silicone oil (5000 cs). The membranes were investigated by light and electron microscopy with respect to silicone oil-specific alterations. The participating cells were differentiated immunohistochemically. Mechanisms of intercellular growth regulation were analyzed by the use of antibodies against cell adhesion molecules and growth factor receptors (PDGFr-B). Most of the membranes showed typical signs of the underlying disease process. However, seven PVR and four diabetic membranes had specific interstitial and intracellular vacuoles which were considered to be silicone oil droplets. The phagocytosing cells were macrophages, partially embedded within vitreous residues. T-lymphocytes can be drawn to the area of macrophage activity by the expression of ICAM-1 and LFA-1. The residual parts of the membranes are typical vitreoretinal membranes. The receptors for PDGF, fibronectin and laminin were negative, but the receptors for collagen and vitronectin were positive within these membranes. The silicone oil-specific macrophage reaction might be supported by emulsified silicone oil droplets, which might get phagocytosed at a certain size. The secondary inflammatory reactions can further enhance silicone oil emulsification and start a vicious circle. Nevertheless, the underlying disease process seems to be much more important in stimulating recurrent membrane formation than silicone oil-specific cell reactions.

Cell Division↗

PubMed1995

Vitreoretinal surgery in intermediate uveitis.

Between 1987 and 1992, vitrectomies were performed in 42 eyes with intermediate uveitis. Pre- and postoperative clinical and ophthalmological parameters were reviewed. Especially the pre- and postoperative time courses of visual acuity were analyzed. We looked for parameters influencing the final visual results. Furthermore, we revised pre- and postoperative recurrent exacerbations of the disease and the duration and dosage of postoperative corticosteroid therapy. The best final visual results were reached in eyes with the best preoperative visual acuities. Anatomic retinal findings and the preoperative duration of intermediate uveitis predominantly influenced the final visual results. Overall, 75% of our patients reached visual acuities of above 20/200. When asked to state their opinion about the final functional result, 80% of the patients were contented. We advocate vitrectomy in patients with intermediate uveitis after intensive follow-up and careful consideration. The anatomic integrity of the retina, a good preoperative visual acuity, and a short preoperative duration of intermediate uveitis are the most important factors influencing the final visual results.

Adolescent↗

PubMed1995

[Surgical extraction of subretinal pseudotumors in age related macular degeneration. Clinical, morphologic and immunohistochemical results].

We extracted massive disciform subretinal lesions in eight eyes of seven patients with age-related macular degeneration via pars plana access. The lesions were 4-12 mm. All eyes had additional pathological findings such as PVR detachments, vitreous hemorrhage or acute submacular hemorrhage, sometimes in combination with each other. In seven eyes the preoperative visual function was no better than perception of hand movements, in 1 eye 1/35. The postoperative visual acuity was in 1 eye 0.3, in 6 eyes between 1/50 and 1/10 and without improvement in 1 eye. An intraocular silicone oil tamponade (highly purified, 5000 cs) was used in all cases. In two eyes the postoperative complication was central submacular fibrosis, and in two eyes with large retinotomies over more than two quadrants there were PVR reactions that needed reoperation in one eye. One patient was operated on bilaterally with final visual acuities of 1/35 and 1/10. The morphological structure of the extracted disciform lesions was characterized by a central fibrotic zone surrounded by attached hematomas, which were organized from the central tissue. In the central parts histology showed single layers of pigmented cells arranged along a basal membranelike PAS-positive band. Cell differentiation revealed macrophages, fibroblasts, myofibroblasts, T-lymphocytes, and vascular cells with immunohistochemical positive stainings for CD 68, cytokeratin, vimentin, alpha-actin, UCHL-1, and factor VIII. The lesions were supplied by a main choroidal vessel with branches into the periphery of the tissue. This feeder vessel can cause severe intraocular hemorrhage when it ruptures during surgical tissue extraction. Further immunohistochemistry showed the presence of cell adhesion molecules such as fibronectin, VLA-2, VLA-5, and VLA-6, the vitronectin receptor, 1CAM-1, LFA-1, and the PDGF receptor B. Their presence reflects mechanisms of growth regulation. The surgical extraction of massive submacular disciform lesions is part of the treatment of selected cases of end stages in age-related macular degeneration.

Aged↗

PubMed1995

[Primary vitrectomy in rhegmatogenous retinal detachment].

For therapy of uncomplicated rhegmatogenous retinal detachment, a buckling procedure is the standard surgical technique today. In complicated cases, e.g., retinal redetachment after a failed buckling procedure, vitrectomy is established. Meanwhile it is being discussed whether or not certain retinal detachments, e.g., with atypically large tears, should be treated with primary vitrectomy. We studied retrospectively all primary vitrectomies for retinal detachment without proliferative vitreoretinopathy (PVR) that were operated upon during 1992 in Würzburg Eye Hospital (32 patients). In 56% (18 eyes) of the patients a subtotal or total retinal detachment was seen preoperatively; in 47% (15 eyes) the macular region was detached. In 25% (8 eyes) large retinal tears were seen (> 1 h). The other patients showed atypical horseshoe tears partly central to the equator or multiple holes. Seventy-eight percent (25 eyes) of all cases were successfully vitrectomized with one operation and revealed good results using intraocular tamponade (SF-6/air mixture). Seven patients needed further vitrectomy partly using silicone oil as an intraocular tamponade. In cases of rhegmatogenous retinal detachment with atypical tears or non-identified holes, vitrectomy without the buckling procedure is a good alternative, because the rate of successful results is as high as what is achieved with buckling procedure in uncomplicated cases.

Adult↗

PubMed1994

Prognostic factors in vitreous surgery for proliferative diabetic retinopathy.

A total of 25 proliferative diabetic eyes of 24 patients scheduled for vitrectomy were examined. The overall preoperative visual acuity was below 0.1, corresponding to hand movement in most patients because of intravitreal hemorrhage. Hence, funduscopy was not possible. The following tests were performed in addition to standard clinical examination: Purkinje entoptic phenomenon, laser interferometry, perception of color flashes, and flicker-VEP using 1.8, 7.6, 15, and 30 Hz as stimulating frequencies. Only the flicker-VEP revealed results predicting reliably the functional visual outcome at 6 months after vitrectomy. Patients with a positive preoperative response to 15 or 30 Hz had a significantly (P < 0.05) better visual outcome at 6 months after vitrectomy (mean postoperative visual acuity 0.11; 95% confidence interval, 1/25-0.32) as compared with patients showing a positive preoperative VEP-response to only 1.8 and 7.6 Hz (mean postoperative visual acuity, hand movement; 95% confidence interval, light without projection--1/35). The flicker-VEP can give additional information about the integrity of the retina and the function of the optic nerve and can therefore help the surgeon to predict the functional result after vitrectomy.

Adult↗

PubMed1994

[Results of pars plana vitrectomy with intraocular SF-6 gas tamponade in complicated retinal detachment].

Vitrectomy following complicated retinal detachment (PVR, giant tears, persistent retinal detachments or redetachments) has become standard in ophthalmic surgery. Intraocular tamponade is performed with gas (e.g. SF-6) or silicone oil. We retrospectively analyzed our functional and anatomical results after vitrectomy with SF-6 gas tamponade in complicated cases of retinal detachment. Ninety-four severe retinal detachments in 85 patients were treated by vitrectomy using SF-6 gas tamponade in the period from July 1990 to June 1991. In 68% of eyes complete retinal reattachment was achieved with the use of SF-6 gas. Thirty-two per cent of the operated eyes developed retinal redetachment an average of 3.4 weeks after initial surgery; 27% of those eyes were treated again with the use of silicone oil. The success rate using vitrectomy with SF-6 gas ranged between 46% and 74%, depending on pathogenetic factors. The best results were obtained in patients receiving primary vitrectomy for complicated retinal detachment. It is concluded that SF-6 gas is a successful tool in the treatment of severe retinal detachment with primary vitrectomy. In cases of persistent or recurrent detachment of the retina the results are not equally good and these cases merit consideration of silicone oil tamponade, depending on the severity of the disease process. However, no definite preoperative criteria for the success of vitrectomy and gas tamponade were identified.

Follow-Up Studies↗

PubMed1992

Intercellular adhesion molecule-1 (ICAM-1) and leukocyte function-associated antigen-1 (LFA-1) expression in human epiretinal membranes.

Various histogenetically different cell types such as macrophages, retinal pigment epithelial cells, glial cells, and fibroblasts are involved in the formation of epiretinal membranes. In the development of such multicellular tissues, cellular adhesion molecules (CAMs) are necessary for cell migration, proliferation, and localization, and the transfer of information between the cells. We investigated the expression of the intercellular adhesion molecule 1 (ICAM-1) and the leukocyte function-associated antigen 1 (LFA-1) in frozen sections of epiretinal membranes in proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR), macular pucker, and recurrent membranes after intraocular silicone oil tamponade using the indirect immunoperoxidase method. ICAM-1 forms a receptor-ligand pair with LFA-1 and is involved in a number of significant cellular interactions, e.g. in providing dynamic position-specific information to guide lymphocyte and leukocyte localization in the immune response. ICAM-1 is a member of the immunoglobulin gene super-family of CAMs. LFA-1 is a member of the integrin family of cell membrane receptors. It mediates a wide range of lymphocyte, monocyte, natural killer cell, and granulocyte interactions with other cells in immunity and inflammation, and it is a receptor for ICAM-1. The LFA-1 interaction with its ligand ICAM-1 mediates not only cell adhesion but also signal transduction in immunologic and inflammatory cell responses. Basal ICAM-1 expression is normally low on nonhematopoietic cells, but it can be subject to an up-and-down regulation by various cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗

PubMed1992

Problems and timing in the removal of silicone oil.

The risk associated with silicone oil removal after complex vitreoretinal surgery is unclear. Therefore, a cohort of 87 consecutive cases of silicone oil removal were analyzed. Eyes with attached retina before silicone oil removal with a follow-up of at least 5 months were included into the study. Forty-eight eyes had severe proliferative diabetic retinopathy; 39 eyes had complex proliferative vitreoretinopathy or giant retinal tears after trauma. Additional clinical features included the presence of a secondary cataract or secondary glaucoma in some eyes. The rate of postoperative complications was different in the two groups: 75% of proliferative diabetic retinopathy patients remained attached; of proliferative vitreoretinopathy patients, only 48.5% remained stable. Whereas success was independent of the duration of intraocular silicone oil tamponade in proliferative diabetic retinopathy, removal of silicone oil was more successful in cases of proliferative vitreoretinopathy in which there was a longer period of silicone oil tamponade. Complications occurring usually were severe and led to a loss of visual acuity. The removal of silicone oil from eyes with secondary glaucoma resulted in an improvement in 68% of patients. The rate of vitreoretinal complications after silicone oil removal, even in cases with a clinically stable-appearing retina, is rather high. Silicone oil removal therefore has to be considered a procedure posing new and ill-defined risks, especially if the indications for the use of silicone oil as an internal tamponade are rather strict. Exact criteria for the timing and safe removal of silicone oil in these complex vitreoretinal disorders still need to be defined.

Adult↗

PubMed1992

Experimental evaluation of in vitro stability of purified polydimethylsiloxanes (silicone oil) in viscosity ranges from 1000 to 5000 centistokes.

One of the main problems in the clinical use of silicone oil in vitreoretinal surgery is the instability of the material in terms of emulsification. Fine silicone oil droplets can cause a secondary glaucoma by blocking aqueous outflow. Intravitreally applicable silicone oils comprise an inhomogeneous group of materials, and the rate of emulsification depends on the physicochemical properties of the silicone oils. Clinically most frequently used silicone oils are highly purified polydimethylsiloxanes with a viscosity of 1000 centistokes (cs) to 5000 cs. Low-viscosity silicone oils are preferred by some surgeons because of easier surgical handling and easier removal out of the vitreous. The authors investigated highly purified polydimethylsiloxanes in viscosity ranges of 1000 cs, 2000 cs, 3000 cs, 4000 cs, and 5000 cs with regard to their in vitro stability to evaluate the optimal range of viscosity with acceptable material stability. The comparative stability tests were performed with 0.1% salt solutions of albumin, acidic alpha-1-glycoprotein, fibrin, fibrinogen, gamma globulins, and very-low-density lipoprotein as emulsifiers. Silicone oil at 5000 cs was in all cases distinctly more stable than the silicone oils with a viscosity up to 4000 cs. A positive correlation between the degree of viscosity and an increase of material stability was not found with all emulsifiers. When very-low-density lipoprotein, albumin, and fibrin served as detergents, a remarkable stability gain was achieved only at 5000 cs.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Proteins↗

PubMed1992

Proliferative activity and immunohistochemical cell differentiation in human epiretinal membranes.

Epiretinal membranes are a complex tissue mainly formed by the proliferation of retinal pigment epithelial cells, macrophages, glial cells, and fibroblasts. The proliferative contribution of these cells in regard of the formation of an epiretinal membrane is not yet clear. We determined the cellular proliferative activity by the use of the monoclonal antibody Ki-67 in 46 epiretinal membranes of proliferative vitreoretinopathy (PVR), PVR recurrences after intraocular silicone oil tamponade, proliferative diabetic retinopathy, and macular pucker. The proliferative activity of each membrane was indicated by the proliferative index (PI), which is the ratio of the actively proliferating Ki-67-positive cells and the total cell number in a cross-section of the membrane. The PI of each membrane was combined with the expression pattern of cell type associated antigens like cytokeratin for epithelial-like cells, KiM7 for macrophages, and glial fibrillary acidic protein for glial cells. Such a membrane typing revealed distinct interindividual differences, but no strict correlation with the underlying disease process. Our findings support the idea of an individual "fingerprint-like" membrane typing at the time of surgery combining the information about the antigen expression pattern of the participating cells and their functional proliferative state. Individual membrane typing for each patient might become clinically significant as soon as the dominating cells for tissue proliferation become key targets for specific pharmacological interventions.

Cell Differentiation↗

PubMed1992

Proliferative activity in epiretinal membranes. The use of the monoclonal antibody Ki-67 in proliferative vitreoretinal diseases.

Epiretinal membranes occur in a number of pathogenetically different diseases, such as proliferative vitreoretinopathy (PVR), proliferative diabetic retinopathy (PDR), macular pucker, and ischemic, inflammatory, and degenerative vitreoretinal disorders. The formation of epiretinal membranes is characterized by the proliferation of histogenetically different cell types. Knowledge of the proliferating potential of surgically excised epiretinal membrane tissue might be clinically relevant to determine which patients face a high risk of recurrences. The monoclonal antibody Ki-67 specifically stains a cell-cycle associated nuclear antigen that is only expressed by cells in the G1, S, and G2/M phases of the cell cycle. With this antibody, the actively proliferating growth fraction can be stained in frozen tissue samples of surgically removed epiretinal membranes by the indirect immunoperoxidase method. In this study, the monoclonal antibody Ki-67 was used to screen 37 epiretinal membranes in PVR, PDR, macular pucker, and in recurrences after intraocular silicone oil tamponade for the presence of actively proliferating cells. Additionally, the number of Ki-67 positive cells in a section of the membrane was quantitatively set in relation to the total cell number of this section. Thus a proliferative index (PI) was ascribed to each membrane as a decimal quotient. The proliferative indices can be graded into four subgroups for missing or very low (PI less than 0.1), low (PI 0.1-0.3), moderate (PI 0.3-0.6), and high (PI greater than 0.6) proliferative activities. High proliferative activities were found in 4 of 5 PVR membranes, in 9 of 14 PDR membranes, in 6 of 11 recurrent membranes after intraocular silicone oil tamponade, and in 2 of 6 macular pucker membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗

PubMed1991

Immunohistochemical localization of epidermal growth factor receptor in a human epiretinal membrane.

Cell growth in proliferative vitreoretinopathy (PVR) is activated by naturally occurring mitogenic substances; thus, growth factors seem to play an important role in PVR. Cell activation by growth factors requires the presence of specific cell-bound receptors by which the mitogenic signal is transmitted. Using the indirect immunoperoxidase method, we investigated frozen sections of 15 epiretinal membranes in PVR for the presence of epidermal growth factor receptor (EGFR), which is commonly utilized by epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha). This receptor could be localized only in one epiretinal membrane. The receptor-bearing cells stained positively for vimentin, cytokeratin, and macrophage marker Ki-M7, indicating that they most probably correspond to transformed macrophages. They stained negatively for desmin and glial fibrillary acidic protein. The cells were embedded in a fibronectin-positive intercellular matrix and were in an actively proliferating state as demonstrated by positive staining for the nuclear proliferation marker Ki-67. We propose that EGFR might be expressed only in certain as yet undefined stages of PVR.

Autoantigens↗

PubMed1991

Emulsification of silicone oils with specific physicochemical characteristics.

To determine the exact role of various factors in silicone-oil emulsification, we investigated eight different silicone oils with specific physicochemical characteristics in terms of their rate of emulsification. The silicone oils were defined by viscosity, volatility, amount of low-molecular components, electrical resistivity, degree of purification and chemical composition. The viscosities differed between the ranges of 1000 and 10,000 cs. The silicone oils included purified polydimethylsiloxane (PDMS), hydroxyl-enriched PDMS and trimethylsiloxy-terminated polydiphenylsiloxane (PDPS). As emulsifiers we used 0.1% solutions of fibrinogen, fibrin, gamma globulins, acidic alpha-1-glycoprotein, very-low-density lipoprotein and serum dissolved in sterile, distilled water as well as in balanced salt solution. The group of low-viscosity silicone oils (1000 cs) was least stable. The greatest difference in stability was found among purified PDMS, having viscosities between 1000 and 5000 cs. The most stable oil was purified PDMS, whose emulsification rate was almost identical at 5000 and 10,000 cs. High contents of hydroxyl end groups enhanced silicone-oil emulsification to a greater extent than did phenyl side groups. The strongest emulsifiers were fibrinogen, fibrin and serum, followed by gamma globulins, very-low-density lipoprotein and acidic alpha-1-glycoprotein. Balanced salt solution accelerated silicone oil emulsification in all cases. For reduction of emulsification in vivo, purified PDMS of high viscosity should be used. Biologically active emulsifiers found in hemorrhages or inflammatory situations might be lowered in vivo by hemostasis and sufficient postoperative anti-inflammatory therapy.

Electrolytes↗

PubMed1991

[Clinical use and results of trans-scleral Nd-YAG cyclophotocoagulation in therapy-refractory glaucoma].

We report on our results of transscleral Nd-YAG-cyclophotocoagulation on 27 eyes with refractory glaucoma. Cyclophotocoagulation was performed with similar parameters according to our findings of morphological investigation in normal human donor eyes. 9 eyes had hemorrhagic glaucoma, 10 eyes had secondary glaucoma after intraocular silicone oil tamponade because of proliferative diabetic retinopathy or because of complicated retinal detachment with proliferative vitreoretinopathy. None of the patients in this group had silicone oil in the anterior chamber, silicone oil emulsification and only one eye had rubeosis iridis. The third group of 8 eyes had glaucoma with aniridia, post-traumatic or postinflammatory glaucoma, glaucoma after extraction of a congenital cataract and one eye with an absolute painful pseudoexfoliation glaucoma. The effects were applied coaxially through the conjunctiva at 1 to 1.5 mm distance from the limbus. The energy was between 3.8 and 4.2 Joules, the exposure time was 10 ms. The focus of the laser beam was placed 3.6 mm posteriorly with a focus adjustment of 9 at the LASAG Microruptur 2. The mean postoperative observation period was 7.5 months. Among the group of hemorrhagic glaucomas the intraocular pressure could in 78% be lowered below 22 mmHg, in 60% among the secondary glaucomas after intraocular silicone oil application and in 50% among the heterogenous third group. In eyes with preceding cyclocryocoagulation 82% fulfilled this criterion. The intraocular pressure stayed stable after 4 weeks at a mean level of 40% below the preoperative values. In all cases the intraocular pressure was at least lowered by 14 mmHg. Vision was reduced in three eyes by the underlying disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

[Possibilities of silicone oil removal after complex vitreoretinal surgery].

The question of the long-term risks and benefits of silicone oil removal after complex vitreoretinal surgery involving the use of silicone oil has not yet been answered. A consecutive series of 50 eyes from which silicone oil had been removed were therefore analyzed in a retrospective study. In all cases the retina was completely attached and seemed to be stabilized before silicone oil removal. The reasons for the original surgery were severe proliferative diabetic retinopathy (PDR) in 20 cases and proliferative vitreoretinopathy (PVR) in 30, in 2 of which PVR developed after perforating injuries. Silicone oil was removed because the retina was clinically stable and completely attached, and in some cases cataract or glaucoma was present. The complication rate after silicone oil removal in these situations varied widely in dependence on the form of disease. After PDR stable conditions were achieved in 70% of cases after silicone oil removal. After PVR with retinal detachment the situation remained stable in only 50%. The most frequent complication was retinal redetachment because of recurrent PVR, accounting for 80% of all failures. The success rate with silicone oil removal after PDR in this study was independent of the duration of tamponade, which had lasted for about 1 year in most cases. Following PVR, silicone oil removal seems to be more safer after long-term tamponade (22 months) than after a shorter duration (12 months). Secondary glaucoma during silicone oil tamponade could be influenced positively in 70% of all cases by silicone oil removal. Because of the relatively high rate of complications after silicone oil removal, especially in PVR, the indications for removal must be carefully considered.

Adolescent↗

PubMed1991

Age-related macular degeneration: current aspects of pathogenesis and treatment.

About 1.1 million people are estimated to have age-related macular degeneration in West Germany. Anatomical aspects of the normal macula and physiological ageing processes in the retina will be described including alterations in the choroid, in Bruch's membrane, the pigment epithelium and the sensory retina. Risk factors for the development of age-related macular degeneration are age per se, perhaps ethnologic characteristics, ocular characteristics, and perhaps environmental factors. The histopathology of age-related macular degeneration will be shown in respect to the formation of drusen in Bruch's membrane, changes in the retinal pigment epithelium, subretinal scar formation, and the development of subretinal choroidal neovascularisation. The clinical importance of subretinal neovascularisation will be discussed including the indications and problems of laser treatment.

Age Factors↗