Biomedical subjects
Publications and source records attributed to P Kroll.
Ten consecutive cases of giant tears with retinal inversion were easily and successfully treated using vitrectomy and silicone oil injection after repositioning the retina with liquid perfluorocarbon. The good initial results show the interest of this technique compared with earlier manipulations of the retina.
In 20 cases of giant tears with considerable proliferative changes, vitreoretinal silicone-oil-surgery was performed. With liquid perfluorocarbon, the involuted retina could easily be fixed during the operation in its former position without difficulties, before silicone oil as a permanent tamponade was used. The good results prove that more invasive manipulations, which were formerly necessary, become superfluous using this method.
Local cerebral metabolic rate for glucose was studied utilizing 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography (PET) in 14 chronically alcohol-dependent patients and 8 normal control subjects of similar age and sex. Nine of the 14 patients (Group A) had clinical signs of alcoholic cerebellar degeneration, and the remaining 5 (Group B) did not have signs of alcoholic cerebellar degeneration. PET studies of Group A revealed significantly decreased local cerebral metabolic rates for glucose in the superior cerebellar vermis in comparison with the normal control subjects. Group B did not show decreased rates in the cerebellum. Both Groups A and B showed decreased local cerebral metabolic rates for glucose bilaterally in the medial frontal area of the cerebral cortex in comparison with the normal control subjects. The severity of the clinical neurological impairment was significantly correlated with the degree of hypometabolism in both the superior cerebellar vermis and the medial frontal region of the cerebral cortex. The degree of atrophy detected in computed tomography scans was significantly correlated with local cerebral metabolic rates in the medial frontal area of the cerebral cortex, but not in the cerebellum. The data indicate that hypometabolism in the superior cerebellar vermis closely follows clinical symptomatology in patients with alcoholic cerebellar degeneration, and does not occur in alcohol-dependent patients without clinical evidence of cerebellar dysfunction. Hypometabolism in the medial frontal region of the cerebral cortex is a prominent finding in alcohol-dependent patients with or without alcoholic cerebellar degeneration.
The occurrence of silicone oil-induced cataract following vitreoretinal silicone oil surgery is an unavoidable complication due the metabolic changes. Following extracapsular cataract extraction, extreme fibrosis und shrinkage of the posterior lens capsule was observed in 7 cases when the oil was left in situ. A new procedure was therefore evolved for correcting refraction following vitreoretinal silicone oil surgery. During vitreoretinal surgery, intracapsular cataract extraction is performed or the pseudophakos is removed. When all retinal interventions have been completed, and at the earliest 3 months after silicone oil removal, anterior lens implantation is performed provided the retina is stable.
In 10 cases, aphakia after silicone oil surgery was corrected as follows: after completion of all retinal interventions, but not less than 3 months after silicone oil removal, an anterior chamber lens (Kelman Multiflex) was implanted. Binocular vision was interrupted for periods ranging from 4 months to 4.6 years (mean 2 years). Tests of the recovered binocular vision, on average 13 months after implantation of the lens, revealed simultaneous vision in 7 cases and exclusion in 2 (primary amblyopia; secondary divergent squint). Stereoscopic vision of 3800" was achieved in 4 cases, and of 200" in one. Four patients regained measurable fusion, between 6 and 29 diopters.
Cryotherapy is a good method of treating chronic uveitis, because it is minimally invasive and there are normally no complications. It has proved possible to reduce the frequency and intensity of inflammatory episodes, so that in many cases systemic drug therapy is superfluous. Stabilization or even regression of secondary conditions such as cystoid macular edema or cataract has been achieved, a phenomenon also observed among the present authors' own patients. In cases which did not respond to cryotherapy or where there were severe vitreous opacities vitrectomy was performed. A total of 207 eyes were followed up, on average for 1 1/2 years. During this time visual acuity remained stable or improved in 76% of those treated by cryotherapy, and in over 86% of those treated by vitrectomy.
Clinical follow-ups of 235 patients following vitrectomy and silicone oil injection were evaluated with special regard to the occurrence and time course of reproliferations. The total incidence of reproliferations was 33%. The highest rate was found after ocular injuries (47%), followed by rhegmatogenous retinal detachment (30%) and proliferative diabetic retinopathy (23%). In all three groups the incidence of reproliferation was highest during the first three postoperative months. In cases with ocular injuries and rhegmatogenous retinal detachment, the rate of reproliferation was found to be highest during the first postoperative month, while in cases of proliferative diabetic retinopathy the incidence peaked during the second and third months. Therefore, in order to prevent complications due to the silicone oil, the oil should be evacuated between the third and sixth postoperative month.
Within the first three or four days after occurrence of a premacular subhyaloidal hemorrhage, the posterior vitreous boundary layer may be lacerated by argon laser coagulation in such a way that the blood flows into the vitreous body, where it is absorbed within a few weeks. Older premacular hemorrhages under an intact vitreous boundary layer, typically green-white in color, have to be treated by more invasive vitreosurgical procedures.
We examined experimentally the pathomechanism of ocular contusion and its damaging influence on the retina. Therefore, various jabbing instruments were used with which a definite trauma can be obtained. The physical parameters, the localization of the trauma and their importance for the injury and the intraocular pressure were analyzed. We found that the amount of energy has no special influence on the kind of ocular contusion, but that it does influence the dynamics of an injury. In direct trauma, the location where the eye is struck, e.g. the cornea or sclera, plays a decisive role in retinal damage. By means of various measurements of intraocular pressure we were able to prove that in non perforating trauma, the anterior segment, has a buffer function and protects the retina in case of corneal trauma from damage caused by contusion.
During the past six years, visual loss in 60 patients was caused by infectious processes and mucoceles of the ethmoid region, benign paranasal tumours, endocrine ophthalmopathies, head trauma etc. Comparison of preoperative and postoperative visual function in 48 cases treated by decompression of the orbit and in 12 cases treated by decompression of the optic nerve demonstrated visual improvement of 68 percent on average. Surgically, we preferred the transethmoidal route and in some cases the lateral osteoplastic approach. With regard to the success of the surgical therapy, a correlation between the time of manifestation of the visual loss and the time of surgery was found. The results mainly depended on the underlying diseases.
In 61 patients echographically examined in A and AB mode at Münster University Eye Hospital a membrane-like echo was found between the retina and the choroid. The acoustic characteristics were studied. The usefulness for the differential diagnosis of retinal detachment was demonstrated with several situations of the retina. The thickness of the retina and choroid can be measured in routine examinations.
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The decision to treat retinal breaks and degenerations prophylactically should be made with an awareness of the incidence of complications associated with argon laser photocoagulation (ALP). We evaluated retrospectively 2,000 eyes with retinal breaks and degenerations treated with ALP, with follow-up from 6 to 84 months (mean 46 months). The only complications during photocoagulation were petectal intra- and preretinal hemorrhages, which absorbed after a few days. Complications after treatment were limited to epiretinal membrane formation in the macular area in four eyes (0.2%). The applied laser energy in three of these four eyes was significantly greater (mean 34.4 mJ) than in the total 2,000 eyes (mean 7.2 mJ). This finding supports the observation by other authors that extensive photocoagulation is associated with an increased incidence of epiretinal membrane formation.
We have developed an experimental model to show that an additional mechanism apart from absorption by pigment epithelium is responsible for the absorption of subretinal fluid. The cause of a fast diminution of subretinal fluid after a buckling procedure is the prominence of the buckle as an obstacle to fluid movements in the eye. This results in any fluid being pushed through the retinal hole into the vitreous. When the retinal hole is closed by the buckle, the remaining part of the subretinal fluid is slowly absorbed by the pigment epithelium present. We performed a preliminary qualitative and quantitative analysis of the phenomena occurring using the finite element method of Zienkiewicz.
Clinical echographic examinations were performed in 15 cases of traumatic cataract. As a result certain criteria were established which give some information on the condition of the posterior capsule of the lens. Echographic examination prior to reoperation enables the procedure to be optimized with regard to IOL implantation, anterior vitrectomy, or prevention of retinal detachment.
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