Investigation of the refractive index repeatability for tantalum pentoxide coatings, prepared by physical vapor film deposition techniques.

Random effects in the repeatability of refractive index and absorption edge position of tantalum pentoxide layers prepared by plasma-ion-assisted electron-beam evaporation, ion beam sputtering, and magnetron sputtering are investigated and quantified. Standard deviations in refractive index between 4*10-4 and 4*10-3 have been obtained. Here, lowest standard deviations in refractive index close to our detection threshold could be achieved by both ion beam sputtering and plasma-ion-assisted deposition. In relation to the corresponding mean values, the standard deviations in band-edge position and refractive index are of similar order.

Grafting of the posterior cornea. Description of a new technique with 12-month clinical results.

PURPOSE: To describe the technique of grafting only the posterior cornea and to report 12-month clinical results. METHOD: A two-layer technique with an anterior recipient flap created by a microkeratome and a posterior penetrating donor graft allows for a watertight wound closure and at the same time a peroperative correction of astigmatism. Four eyes (3 patients) were followed for 12 months. RESULTS: The surgical technique could be completed in all cases without complications. The postoperative course was uneventful. The intrastromal absorbable sutures disappeared spontaneously and completely. Graft thickness showed the expected 6-month minimum while recipient flap thickness remained constant. After 1 year endothelial cell densities were 1200-2300 cells/mm2. Confocal microscopy showed activated keratocytes in the flap and quiescent keratocytes in the donor tissue by one year. The anterior chamber depth was normal in all cases. The optical quality of the cornea was studied by automatic keratometry and keratoscopy (TMS). The obtained optical properties were not optimal. CONCLUSIONS: The developed novel technique gives a better wound closure and a complication free postoperative course. It may allow for better control of postoperative astigmatism. In order to disseminate the use of the technique, eyebanks should supply posterior corneas to the surgeon.

Corneal transplantation with donor tissue kept in organ culture for 7 weeks.

PURPOSE: To study the fate of corneal grafts after extended organ culture (7 weeks). METHODS: Six patients with symmetrical eye diseases were grafted bilaterally, in one eye with a cornea prepared by routine organ culture (mean 16 days), in the other eye with a donor cornea kept for 7 weeks (mean 49 days) in organ culture. The outcome was evaluated by biomicroscopy, graft thickness, endothelial cell density and visual performance after an observation time of at least 1 year. RESULTS: Penetrating 7-8 mm grafting was uncomplicated in all cases. The endothelial densities were in both groups in the range 1000-2000 cells/mm2, and visual acuity 0.2-0.9 in cases with no other ocular pathology. Postoperative graft thickness and deswelling did not differ between 2- and 7-week cultured corneas. At final examination the thicknesses were 0.50 mm and 0.49 mm for 2- and 7-weeks cultured corneas. CONCLUSION: Seven-week cultured corneas give clinical results comparable to those obtained using shorter culture periods. An extended culture period may be used to improve other qualities of the graft (compatibility, cell number, cell metabolism) and microbiological control.

Beta blockers: evidence versus wishful thinking.

Catecholamines and ischemia play an important role in the induction of ventricular tachyarrhythmias. Beta blockers antagonize the effect of catecholamines and have anti-ischemic properties. Several controlled studies performed in the early 1980s in patients after myocardial infarction have shown that beta-blocker therapy clearly decreases sudden and nonsudden cardiac death. Despite the lack of recent randomized trials, data from uncontrolled studies suggest that the beneficial effect of beta blockers is still present in the thrombolytic era. Thus, it is incomprehensible that today in the United States and in most parts of Europe, < 40% of post-myocardial infarction patients are treated with beta blockers. Even in patients with documented sustained ventricular tachycardias (VTs) or ventricular fibrillation (VF), clinical studies indicate that beta blockers improve survival. Thus, even in the thrombolytic era, beta blockers should be used as a basic therapy in patients who are at risk of sudden cardiac death.

Risk stratification following myocardial infarction in the thrombolytic era: a two-step strategy using noninvasive and invasive methods.

OBJECTIVES: We prospectively performed a two-step risk assessment in patients in the early phase after acute myocardial infarction (MI). BACKGROUND: Noninvasive methods like Holter electrocardiographic monitoring (HM) and determination of the left ventricular ejection fraction (EF) as well as the invasive technique of programmed ventricular stimulation (PVS) have been used to identify patients in the late phase after MI as candidates for prophylactic implantation of a cardioverter/defibrillator. However, it is unclear whether these results can be transferred to patients following acute MI. METHODS: A series of 657 patients with acute MI (< or = 75 years) underwent HM and EF. If one of the two methods yielded abnormal findings (HM > or = 20 ventricular ectopic beats/h/> or =10 ventricular pairs/day/ventricular tachycardia; EF < or = 40%), PVS was done (abnormal PVS: induction of monomorphic ventricular tachycardia, duration >10 s, cycle length > or = 230 ms). RESULTS: Of 657 patients, 304 (46%) had either an abnormal HM or EF. The PVS performed in 146 of 304 patients was abnormal in 22. During a mean follow-up of 37 months, there were 106 (16%) deaths, being sudden in 24 (3.6%), nonsudden cardiac in 45 (6.8%). The incidence of arrhythmic events (sudden cardiac death, symptomatic ventricular tachycardia, cardiac arrest) was 18% (4/22) with an abnormal PVS and only 4% (5/124) with a normal PVS (odds ratio 4.0, p=0.032). CONCLUSIONS: The rate of arrhythmic events is low in post-MI patients in the 1990s. Nevertheless, a two-step risk stratification is helpful in selecting candidates for a defibrillator trial aiming at primary prevention of sudden cardiac death after MI.

Cytomorphometric characterization of NHL(non-Hodgkin's lymphomas) of low and high grade malignancy.

From semithin sections of 12 non-Hodgkin's lymphomas (3 lymphocytic, 3 centrocytic, 3 lymphoblastic, 3 centroblastic m.L.) morphometric parameters of nucleus and cytoplasm, including size, shape, roundness, number and size of nucleoli were measured. Statistical evaluation of the data showed that the lymphoma cells mainly differ in their size, less in their shape. Nucleolar parameters are of greater value than contour features in discriminating the four groups of NHL. With growing grade of malignancy an increasing nuclear and cellular polymorphism was observed. Moreover, measurement of the feature "maximal nuclear diameter" on paraffin sections from 42 further cases showed the possibility of morphometric discrimination of low and high malignant NHL in histopathological diagnostics.