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Biomedical subjects

F H Koch

Publications and source records attributed to F H Koch.

At least 19 recordsLinked to original sources
PubMed2001

Intravitreous injection of tissue plasminogen activator and gas in the treatment of submacular hemorrhage under various conditions.

OBJECTIVE: To investigate the efficacy and safety of treating submacular hemorrhages secondary to age-related macular degeneration (ARMD) with intravitreous recombinant tissue plasminogen activator (rt-PA) and gas under various conditions. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: Forty-three consecutive eyes of 42 patients with recent (range, 2-28 days) subfoveal hemorrhage secondary to ARMD were included in this study. The size of subretinal hemorrhage ranged from 0.25 to 30 disc areas. METHODS: All patients were treated with intravitreous injections of rt-PA (50 microg) and sulfur hexafluoride (0.5 ml). Postoperative prone positioning was maintained for 24 to 72 hours. Patient follow-up ranged from 4 to 18 months (mean, 6 months). MAIN OUTCOME MEASURES: Best and final postoperative visual acuity in relation to size and onset of hemorrhage, displacement of subretinal blood, and surgical complications. RESULTS: Best postoperative visual acuity compared with preoperative visual acuity was improved two or more Snellen lines in 19 eyes (44%) and stable in 24 eyes (56%). Final visual acuity was improved two or more lines in 13 eyes (30%), stable in 26 (61%), and two or more lines worse in 4 eyes (9%). Duration of hemorrhage <or=14 days was associated with a better gain of lines of vision (P = 0.0058). Best postoperative acuity was maintained for an average of 4.2 months (range, 0.5-12 months). Overall, complete displacement of blood from under the fovea was achieved in 35 eyes (81%). Nine eyes (21%) developed recurrent hemorrhage, which required repeat treatment. In three patients (7%), a mild breakthrough vitreous hemorrhage was observed. CONCLUSIONS: Our findings suggest that intravitreous injections of rt-PA and gas are of value for an improved and accelerated visual recovery in ARMD patients with submacular hemorrhage, although final visual outcome is often limited by the progression of the underlying ARMD. Patients with retinal hemorrhages of recent onset (<or=14 days) seem to have the most favorable results. A rapid displacement of submacular blood may reveal discrete choroidal neovascular membranes amenable to further treatment. The complication rate of this minimally invasive technique seems to be low.

Aged↗
PubMed1999

Complications after implantation of intraocular devices in patients with cytomegalovirus retinitis.

PURPOSE: The authors report their surgical experience after sustained-release ganciclovir treatment, as well as replacing empty ganciclovir implants in patients with acquired immune deficiency syndrome (AIDS) and cytomegalovirus (CMV) retinitis. METHODS: Between November 1995 and August 1998, 79 eyes of 49 patients received 99 intravitreal ganciclovir implants. Patients were examined monthly after implant surgery. Follow-up periods ranged from 6 to 128 weeks. RESULTS: At the first 3-week postoperative visit, 73 eyes (97.2%) of 46 patients exhibited stable conditions. In 6 eyes (3.8%) of 3 patients, further progression was noted due to resistance to ganciclovir. The most common early complication (within 6 weeks after implantation) was cystoid macular edema, observed in 7 eyes receiving implants. Retinal detachment was the most common late complication (over 6 weeks after implantation) in 11 eyes. In almost all eyes with CMV retinitis and retinal detachment, involvement of more than 25% of the retina was observed. Additional severe complications included extrusion of the first pellet in 2 eyes and cataract as a late complication in 5 eyes. A total of 28 eyes (35.4%) of 16 patients receiving a second implant did not experience significant three-line loss by the end of the follow-up period. CONCLUSION: In the treatment of CMV retinitis, sustained-release ganciclovir implantation seems to be an alternative to intravenous ganciclovir. Early implantation and additional replacement of the device has the potential to decrease the risk of developing retinal detachment. We would recommend additional systemic antiviral CMV therapy to avoid infection of the fellow eye and CMV disease.

AIDS-Related Opportunistic Infections↗
PubMed1999

[Intravitreal endoscopic visualization of intraocular ganciclovir devices: improved long-term treatment of CMV retinitis].

BACKGROUND: The recent development of 20- and 19-gauge diameter endoscopes allows an excellent direct intravitreal visualization of intraocular morphology. A gradient index (GRIN) endoscope (Insight Instruments, Lake Mary, FL, USA), which combines a small diameter (0.89 mm, 20 gauge) and an exceptional optical resolution, can be used as a diagnostic tool for the assessment of the safety and vitreous interaction of sustained release intraocular devices which have been designed to deliver ganciclovir (Vitrasert) over a period of 8-12 months and were successively implanted in several eyes. PATIENTS AND METHODS: 78 eyes of 49 patients received 100 ganciclovir implants between November 1995 and July 1998. In six patients who received additional implants, the GRIN endoscope was used as an optical control of wound healing processes and Vitrasert positioning after implantation of prior devices (two-point suturing technique). RESULTS: In all of these six eyes, a clinical stabilization of the cytomegalovirus retinitis was noted. Endoscopic observation of the scleral 5-mm incision revealed no gaps after two-point suturing of the device. Only one of six eyes showed significant vitreous tractions around the Vitrasert. However, the struts of all pellets were completely covered by a fibrous membrane. Occasional fibrous plaques were noted on the surface of devices which presumably had been damaged by surgical manipulations. In one case, the endoscopic examination disclosed the suprachoroidal implantation of a device. In this eye, no signs of retinal toxicity or recurrence of CMV retinitis were observed. CONCLUSIONS: High resolution endoscopy of the vitreous cavity appears to be an effective method for the control of intraocular drug delivery devices. Basically, the repeated implantation of intraocular ganciclovir implants can be considered a safe method in the management of relapsing CMV retinitis. However, the endoscopic observation of fibrous membranes covering the struts suggest that the explanation of an intraocular device has the potential for various intraoperative complications (e.g. hemorrhages, traction, tears, retinal detachment). Therefore, we would recommend the additional implantation of further implants rather than a replacement.

Cytomegalovirus Retinitis↗
PubMed1999

Vitreous concentrations of TPA and plasminogen activator inhibitor are associated with VEGF in proliferative diabetic vitreoretinopathy.

PURPOSE: In angiogenesis, matrix degradation is an important step in endothelial cell migration and proliferation. There is evidence that serine proteases, such as tissue plasminogen activator (TPA), urokinase-type plasminogen activator (UPA), and plasminogen activator inhibitor (PAI), are involved in this process. We hypothesized that in eyes in which neovascularization is active, such as in proliferative diabetic vitreoretinopathy (PDVR), vitreous levels of these proteases are increased. Furthermore, correlation was sought between intraocular concentrations of serine proteases and vascular endothelial growth factor (VEGF), a multifunctional cytokine that has been shown to play a major part in mediating active neovascularization in patients with ischemic retinal diseases. METHODS: Undiluted samples of vitreous fluid were obtained from patients who underwent vitreoretinal surgery for PDVR or retinal detachment. Vitreous levels of VEGF, TPA, UPA, and PAI were determined by enzyme-linked immunosorbent assay. RESULTS: We found a statistically significant correlation between levels of VEGF and TPA (P<0.01) and VEGF and PAI (P<0.026) in the vitreous fluid of patients with PDVR. Concentrations of VEGF (P<0.03), TPA (P<0.042), and PAI (P<0.0098) in diabetic eyes were significantly higher than in nondiabetic eyes. Of 14 eyes with PDVR, 6 contained detectable levels of UPA. CONCLUSIONS: A correlation between increased levels of VEGF and TPA or PAI in the vitreous fluid of eyes with PDVR reflects the possible role of plasminogen activators in the progression of this disease. An understanding of the endogenous inhibition of matrix degradation in ocular angiogenesis may be useful in the development of new treatment strategies.

Biomarkers↗
PubMed1999

Visual outcome after treatment with low-dose recombinant tissue plasminogen activator or hemodilution in ischemic central retinal vein occlusion.

The ischemic type of central retinal vein occlusion (CRVO) is associated with a poor visual and ocular prognosis. Although several reports have indicated that hemodilution or thrombolytic therapy may be of benefit, there is still no consensus among ophthalmologists about the management of this disorder. In our study, we retrospectively evaluated the visual outcome after medical treatment in 58 patients with ischemic CRVO and severe visual loss (< or = 20/50). We separately investigated three different groups, depending on the following criteria: onset of symptoms within 11 days prior to admission and thrombolytic treatment with 50 mg of recombinant tissue plasminogen activator (rtPA) and intravenous heparinization (n = 23) or hemodilution therapy (n = 22) or onset of symptoms >11 days before the initial visit and hemodilution (n = 13). An advancement of 2 or more lines on the logarithmic visual acuity chart was noted in 10 cases (44%) in the rtPA group and in 3 subjects (14%) in the early-phase hemodilution group, whereas only 1 patient in the late-phase hemodilution group showed a comparable improvement. Our findings suggest that treatment with low-dose rtPA or hemodilution aimed at early restoration of blood flow has the potential to improve the visual prognosis in ischemic CRVO. The finding that thrombolysis had a favorable outcome supports the hypothesis that specific subgroups of patients may benefit from this therapeutic approach. Further investigation will be required to definitively prove the effectiveness of fibrinolytic agents.

Adult↗
PubMed1997

The influence of intraocular pressure and systemic oxygen tension on the intravascular pO2 of the pig retina as measured with phosphorescence imaging.

The intravascular oxygen tension (pO2) of the pig retina was determined by measuring the phosphorescence lifetime of an intravenously injected dye. Pseudocolor images of the intravascular retinal pO2 were obtained. The method is noninvasive except for the application of the dye. The measurement system was adapted to a fundus camera. The systemic arterial oxygen pressure (PaO2) as well as the intraocular pressure (IOP) were altered. In the measurements the pO2 of the choriocapillaris was close to the systemic PaO2. Under normoxia, the retinal veins showed a lower pO2 of about 40 mm Hg. We found evidence of an autoregulation of the retinochoroidal pO2. The retina and the optic nerve head showed an autoregulation of the intravascular pO2 at low IOP, but were more sensitive to a moderate elevation of the IOP of about 40 mm Hg, as compared to the choroidal pO2. The pO2 of the choriocapillaris seemed to change little until the considerably high IOP value of about 50 mm Hg was attained. This behavior is due to either the high perfusion reserve capacity of the choroid or to autoregulation. Although our experiments refer to the perfusion of the pig eye, the results provide indirect evidence that even during a glaucoma attack the human choroid might be able to maintain a reasonable oxygen supply to the retina, whereas the intravascular pO2 of the retinal vessels and of the optic nerve head decrease strongly. The adaptation to a fundus camera facilitates a future clinical application if a nontoxic dye can be developed.

Animals↗
PubMed1997

Subretinal microsurgery with gradient index endoscopes.

State-of-the-art subretinal surgery involves a standard three-port pars plana entry, followed by an iatrogenic retinotomy to access the subretinal space. Subretinal manipulations through a small retinotomy are made possible by specially designed instruments. As the surgeon looks through the vitreous cavity, all subretinal maneuvers are obscured by the overlying retina. Consequently, the surgeon is operating 'blindly' and has to rely on 'feeling' rather than direct visualization. Micro-endoscopic viewing systems are the ideal solution for visualization during subretinal surgery. Until now, such endoscopes were either too large for intraocular use or lacked sufficient resolution, especially at a short working distance. Recently, a gradient index (GRIN) endoscope was developed (Insight Instruments, Inc., Lake Mary, Fla., USA) combining a small diameter (0.89 mm, 20 gauge) and incorporating excellent optical resolution, even at extremely close working distances. After ballooning a limited part of the retina without creating a retinal hole, the 20-gauge GRIN endoscope can be introduced into the subretinal space through the sclera and choroid, posterior to the pars plana. Surgical instruments can then be introduced into the subretinal space through a second neighboring sclerotomy. Thus, subretinal surgery can be performed under direct endoscopic control. As a result of direct visualization, the surgeon may perform certain surgical procedures with greater accuracy, i.e., subretinal neovascular membranes may be dissected meticulously from the neurosensory retina and retinal pigment epithelium, minimizing damage to both structures. The feeding choroidal vessel can be identified and directly coagulated, which is usually very difficult during conventional subretinal surgery. Endoscopic subretinal surgery is thus a significant improvement over conventional methods, avoiding the need for a retinotomy and increasing the safety and facility of the surgery itself.

Endoscopy↗
PubMed1996

A modified technique of impression cytology to study the fine structure of corneal epithelium.

In this article, the development and application of a modified technique of impression cytology for the electron-microscopic examination of corneal epithelium is presented. Corneal epithelium of controls and diabetic patients was obtained using millipore filters, which had been presoaked with EDTA to weaken intercellular adhesions. Light and electron microscopy (EM) of the control samples showed sheets of well-preserved corneal epithelial cells. Therefore, this modified technique is supposed to be useful for the analysis of alterations of the corneal epithelium. EM of corneal cells of diabetic patients showed irregularly formed epithelial cells. The corneal epithelium of diabetic patients revealed thickening of the basement membrane and a decreased number of hemidesmosomes. The alterations observed in specimens of diabetic patients represent the morphological equivalent of an impaired epithelial barrier function, an increased fragility of epithelial lining and the disturbed healing properties occurring in diabetic keratopathy.

Adolescent↗
PubMed1996

Effects of different antioxidants on lens-induced uveitis.

For evaluation of the effects of different free-radical scavengers on biochemical changes in lens-induced uveitis (LIU), ten male Wistar rats were sensitized for 8 weeks using bovine lens protein and Freund's adjuvant. The uveitis was induced by disruption of the lens capsule. One group of animals received superoxide dismutase and catalase (SOD/CAT); a second group of animals was treated with vitamin E. Lipid peroxides (LPO) of the retinal tissue and aqueous humor served as parameter of oxidative tissue damage. Glutathione (GSH/GSSG) of the aqueous humor was evaluated as a parameter of the tissue's redox state. For evaluation of the inflammatory response, myeloperoxidase activity (MPO) was determined in the iris/ciliary-body complex. SOD/CAT produced no improvement in the significantly (P < 0.05) elevated MPO and LPO values recorded for untreated control animals. Following vitamin E treatment the GSH/GSSG and LPO values in aqueous humor were markedly improved as compared with controls. Retinal LPO values were significantly (P < 0.05) reduced as compared with controls. No change in MPO levels was observed. The results demonstrate that enzymes such as SOD and CAT do not influence tissue damage at a significant level, whereas radical chain breakers such as vitamin E can do so. However, the inflammatory response itself is not reduced. To achieve global results, drugs are necessary that act on both free radicals produced by noninflammatory pathways and those originating from inflammation.

Animals↗
PubMed1995

Oxidative reactions in the tear fluid of patients suffering from dry eyes.

PURPOSE: To evaluate whether products of oxidative and inflammatory reactions are detectable in the tear fluid of patients suffering from dry eyes. METHODS: The tear fluid of 217 patients (397 eyes) was sampled. Criteria for grouping of the patients were (1) basic secretion test ("sicca 1": BST = 0-5 mm, n = 78 eyes; "sicca 2": BST = 6-10 mm, n = 109 eyes) and (2) subjective symptoms (normal BST, burning, foreign body sensations, tearing, dryness of the eyes: n = 78 eyes). One group of healthy patients (normal BST, n = 132 eyes) served as controls. Lipid peroxide levels and myeloperoxidase activity, as parameters for oxidative tissue damage and inflammatory activity, were determined in the tear fluid. Those patients whose consent could be obtained were subjected to the rose bengal test (sicca 1: 56 eyes; sicca 2: 97 eyes; subjective symptoms: 44 eyes; controls: 49 eyes). The correlation between BST and rose bengal test results was calculated. RESULTS: Lipid peroxides were significantly (P < 0.05) higher in the groups sicca 1 and subjective symptoms than in healthy controls, as was the inflammatory activity in groups sicca 1, sicca 2 and subjective symptoms. Additionally, the inflammatory activity in the group sicca 1 was significantly (P < 0.05) higher than in the groups sicca 2 and subjective symptoms. No evidence of a significant correlation between BST and rose bengal test results was observed. CONCLUSIONS: Both oxidative tissue damage and polymorphonuclear leukocytes indicating an oxidative potential occur in the tear film of patients suffering from dry eyes. These reactions lead to severe damage of the involved tissue. Free radicals and inflammation may be involved in the pathogenesis or in the self-propagation of the disease.

Dry Eye Syndromes↗
PubMed1995

Local effects of different perfluorochemical agents.

PURPOSE: To clarify whether the prolonged presence of perfluorochemicals (PFC) in the vitreous cavity causes oxidative tissue damage and inflammatory response of the retina and, if so, what the process is. METHODS: After three different perfluorochemicals [perfluorodecalin (C10F18), perfluorooctane (C8F18) and Fluosol-DA (corresponding to a 20% emulsion of 70% PFD and 30% perfluorotripropylamine, C9F21N)] had been in the vitreous cavity of rabbits for 2 weeks, lipid peroxide concentration and myeloperoxidase activity in the retina were determined. RESULTS: Whereas only Fluosol-DA showed significant oxidative damage, the inflammatory activity was significantly increased in all groups. CONCLUSION: The increased myeloperoxidase activity and the observed oxidative damage of the retina seem to be the effect of both perfluorochemical-loaded macrophages and inflammatory-induced lipid peroxidation.

Animals↗
PubMed1995

Systemic effects of different perfluorochemical agents.

PURPOSE: An intravitreal injection of Fluosol-DA leads to a higher alteration of the macrophage system of the retina than perfluorooctane and perfluorodecalin administered by the same route. The difference may be due to different kinds of oxidative damage caused by the three chemicals. To test the validity of this assumption, the degree of cell alteration, expressed as reduction of cytoplasmic motility, caused by these three perfluorochemicals was examined. METHODS: Using the hepatic macrophage system of the rat, cell alteration was examined by magnetometry after intravenous application of various perfluorochemicals [emulsified perfluorodecalin (C10F18), perfluorooctane (C8F17Br) and Fluosol-DA (corresponding to a 20% emulsion of 70% perfluorodecalin and 30% perfluorotripropylamine, C9F21N)]. RESULTS: After administration of high doses, all perfluorochemicals led to cytoskeleton alteration. This alteration, expressed as retardation of the relaxation period of ferromagnetic iron oxide particles, was most pronounced after administration of Fluosol-DA. CONCLUSION: The compromising effect of perfluorochemicals is dose dependent and differs among the three compounds tested, with Fluosol-DA showing the greatest decrease in cytoplasmic motility.

Animals↗
PubMed1995

Pars plana incisions of four patients: histopathology and electron microscopy.

The pathology of pars plana incisions of four patients is described: three with light microscopy and one with light and electron microscopy. Two eyes were removed because of choroidal melanoma, immediately and 8 days after vitrectomy and transvitreous retinal biopsy. Considerable disruption of tissues surrounding the pars plana incisions was observed. Vitreous was incarcerated in the wounds, which healed with granulation tissue. One eye was examined 4 months after vitrectomy for diabetic retinopathy and a failed pars plana filtering operation. It contained fibrovascular ingrowth from all the incisions, infiltrating the vitreous base with granulation tissue and causing vitreous haemorrhage and retinal detachment. One eye was removed 1 year after vitrectomy for anterior hyaloidal fibrovascular proliferation and early phthisis. The wound had fibrous ingrowth histologically and evidence of active fibroplasia.

Adult↗
PubMed1994

No cataract two years after pneumatic retinopexy.

PURPOSE: This study was conducted to examine possible adverse effects on lens transparency caused by pneumatic retinopexy using sulfur hexafluoride gas. METHODS: In a prospective study, both lenses of 33 patients undergoing pneumatic retinopexy in one eye were monitored up to 24 months postoperatively by slit-lamp examination and Scheimpflug photography. RESULTS: Pneumatic retinopexy does not cause significant lens opacifications up to 2 years after surgery. CONCLUSION: Temporary gas tamponade for pneumatic retinopexy is not associated with permanent changes in lens transparency.

Adult↗
PubMed1993

The retinal irradiance and spectral properties of the multiport illumination system for vitreous surgery.

The multiport illumination system was developed as a fiberoptically illuminated pars plana cannula system for vitreous surgery. The retinal irradiance of the multiport illumination system and several other commonly used endoilluminators (light pipes) measured at 5 mm are comparable, ranging from 94 to 256 mW/cm2. In the actual surgical setting, however, the retinal irradiance of the multiport illumination system is far less (56 mW/cm2) because the end of the fiberoptic cables are fixated in the pars plana 16.5 mm away from the retinal surface. A reduction in the maximal intensity (100%) to 50% reduces the retinal irradiance by approximately two thirds to 3.7 mW/cm2. The light emitted by the multiport illumination system used in conjunction with a long-wave pass filter with a cutoff wavelength of 420 nm reduces the amount of short-wavelength light by one third to about 4% of the overall irradiance.

Eye Diseases↗