Incidence of Retinal Detachment after Macular Surgery. / Ablatiohäufigkeit nach elektiver Makulachirurgie.

Macular surgery has become an increasingly atraumatic procedure for the eye with the surgical methods that have been further developed in recent years. The most common complications include cystoid macular oedema and retinal detachment, more rarely endophthalmitis. The aim of this retrospective study is to record the number of retinal detachments following elective macular surgery. In this study we included all patients who underwent pars plana vitrectomy (ppV, 20 or 25 gauge) in the years 2009 - 2016. We then identified the patients who were hospitalised again because of retinal detachment. For the affected patients, the rate of retinal detachment, functional outcomes and possible risk factors were recorded. A total of 904 eyes were identified, of which 667 had surgery for epiretinal membrane, 188 for macular hole, and 49 for vitreomacular traction with a 20 or 25 gauge ppV. Of these 904, retinal detachment occurred in 17 (1.88%) cases. The mean time between first ppV and second ppV with retinal detachment was 248 days (3 - 1837 days). Two of the 17 patients had at least one retinal break before or during surgery. The retinal break was located inferior in six cases, superior in four; in four cases PVR retinal detachment and in three cases the foramina were distributed. Mean visual acuity was 0.27 (decimal) before macular surgery and 0.28 at the time of last presentation. Modern vitrectomy techniques reduce the complications in elective macular surgery, but do not replace the surgeon's experience.

Novel ultrasonic in-die measurements during powder compression at production relevant speed.

A novel ultrasonic instrumentation was successfully implemented in a compaction simulator. A through-transmission set-up was realised with longitudinal and transverse transducers being alternately positioned inside Euro-D-modified punches. Key features of the data acquisition are described. Considerable attention was paid to an accurate displacement measurement and a synchronic acquisition of the ultrasonic signal. Vivapur 102 and Di-Cafos A150 were chosen for evaluation. In contrast to other published instrumentations, production-relevant powder densification speeds were feasible whilst featuring outstanding measurement precision. Maximum ultrasonic speed was achieved at maximum density. Materials differed considerably regarding the slope of the decompression phase, which might be suitable for assessing elasticity and speed sensitivity of powders or formulations without compressing twice. The developed set-up furthermore enables in-die measurements of apparent Young's modulus and apparent Poisson's ratio (i.e. their change throughout the course of the tableting process). Young's modulus increased upon densification and values match with literature data. Poisson's ratio increased linearly as a function of solid fraction for plastically deforming Vivapur 102, whereas it was practically constant for brittle Di-Cafos A150. Increased mechanistic understanding of deformation factors (e.g. rearrangement, fragmentation, elasticity) and estimation of mechanical compatibility of mixtures, is feasible. Moreover, in-die Young's modulus and Poisson's ratio are valuable for compression simulations based on finite or discrete element method.