Stefan J. Lang

Analysis of the changes in keratoplasty indications and preferred techniques.

Background Recently, novel techniques introduced to the field of corneal surgery, e.g. Descemet membrane endothelial keratoplasty (DMEK) and corneal crosslinking, extended the therapeutic options. Additionally contact lens fitting has developed new alternatives. We herein investigated, whether these techniques have affected volume and spectrum of indications of keratoplasties in both a center more specialized in treating Fuchs’ dystrophy (center 1) and a second center that is more specialized in treating keratoconus (center 2). Methods We retrospectively reviewed the waiting lists for indication, transplantation technique and the patients’ travel distances to the hospital at both centers. Results We reviewed a total of 3778 procedures. Fuchs’ dystrophy increased at center 1 from 17% (42) to 44% (150) and from 13% (27) to 23% (62) at center 2. In center 1, DMEK increased from zero percent in 2010 to 51% in 2013. In center 2, DMEK was not performed until 2013. The percentage of patients with keratoconus slightly decreased from 15% (36) in 2009 vs. 12% (40) in 2013 in center 1. The respective percentages in center 2 were 28% (57) and 19% (51). In both centers, the patients’ travel distances increased. Conclusions The results from center 1 suggest that DMEK might increase the total number of keratoplasties. The increase in travel distance suggests that this cannot be fully attributed to recruiting the less advanced patients from the hospital proximity. The increase is rather due to more referrals from other regions. The decrease of keratoconus patients in both centers is surprising and may be attributed to optimized contact lens fitting or even to the effect corneal crosslinking procedure.

State and regional actors in complex governance systems: Exploring dynamics of international negotiations

Over the last decades, the number of international organizations (IOs) and regional groups (RGs) increased tremendously, and states are now simultaneously members of several RGs and IOs. This article inquiries how states act in settings of complexly nested and overlapping institutions on the regional and international levels. How frequently do states voice regional positions in international negotiations and why are some more active in this respect than others? Why are some RGs more vocal than others? Multiple state memberships in RGs foster the regionalization of international negotiation dynamics via burden-sharing mechanisms. In addition, state capacity and power, the age and policy scope of RGs and the institutional design of IOs also shape negotiation dynamics. This article concludes with reflections on implications of regionalized international negotiations for the efficiency and legitimacy of governance beyond the nation-state.

Regional actors in the United Nations: exploring the regionalization of international negotiations

Traditionally, international organizations (IOs) are arenas for state–state cooperation, but more often than not regional organizations and groups (ROs) can acquire formal status within IOs (e.g. observer). Studying the behaviour of 62 ROs in 19 UN umbrella organizations over more than 350 individual negotiations, this article provides comparative insights into the current pattern of regionalization of international negotiations. We seek to account for the observed variation in the extent of regionalization of international negotiations. Thus, we examine which institutional design features are conducive for the regionalization of IO negotiations. We show that large IOs with majority rules in place render regionalization of negotiations more likely, while the formal openness of an IO for ROs does not have a positive effect. This is not the least due to the inclination of ROs to engage in forum shopping, especially when they have access to multiple venues.

Cell-by-cell alignment of repeated specular microscopy images from the same eye.

Purpose Modern specular microscopes (SM) robustly depict the same central area of the corneal endothelium at different time points through a built-in fixation light. However, repeated image acquisitions slightly shift and rotate because of minute changes in head position in the chin and forehead rest. This prevents the manual retrieval of individual corneal endothelial cells (CECs) in repeated measurements because SM images usually lack obvious landmarks. We devised and validated an image registration algorithm that aligns SM images from the same eye to make corresponding CECs coincide. Methods We retrospectively selected 27 image pairs for the presence of significant image overlap. Each image pair had been recorded on the same day and of the same eye. We applied our registration method in each image pair. Two observers independently validated, by means of alternation flicker, that the image pairs had been correctly aligned. We also repeatedly applied our registration method on unrelated image pairs by randomly drawing images and making certain that the images did not originate from the same eye. This was done to assess the specifity of our method. Results All automated registrations of the same-day and same-eye image pairs were accurate. However, one single image incorrectly failed to trigger the non-match diagnosis twice in 81 registration attempts between unrelated images. As it turned out, this particular image depicted only 73 CECs. The average number of CECs was 253 (range 73–393). Conclusion Repeated non-contact SM images can be automatedly aligned so that the corresponding CECs coincide. Any successful alignment can be considered as proof of the retrieval of identical CECs as soon as at least 100 CEC centroids have been identified. We believe our method is the first to robustly confirm endothelial stability in individual eyes.

Qualitätsmessung aus Routinedaten

There is a growing interest in quality measurement in the healthcare sector. Hospitals in Germany are obligated to participate in measures for external quality assurance and they must establish an internal quality management system. In addition to the legal requirements, measurement of quality is also possible with routine data. Suitable sources are the ICD system or unstandardized information from treatment documentation. The selection of suitable quality indicators is necessary to interpret the data. Complications or achievement of surgical objectives can be suitable quality indicators. Analysis of procedures or the assessment of waiting time are also possible indicators. Our first data concerning waiting time show that with increasing use of an electronic patient guidance system, the waiting time decreased in our outpatient department. Assessment of quality indicators from routine data enables a continuous measurement of quality over a long period. Measures to increase quality can easily be checked. Routine data also provide the possibility to participate in a public reporting of quality indicators.

Simultaneous Transplantation of Limbal Stem Cells May Reduce Recurrences of Granular Dystrophy After Corneal Transplantation: 2 Long-Term Case Reports

AbstractTo present 2 cases with long-term relapse-free intervals only after limbo-keratoplasty but not after conventional penetrating keratoplasty in granular dystrophy.Retrospective review of the patient charts and photographs taken during long-term follow-up of 2 cases with granular dystrophy, in which 1 eye received penetrating keratoplasty and the fellow eye received penetrating limbo-keratoplasty.In the first patient, 1 eye showed extensive recurrence of granular deposits 17 years after penetrating keratoplasty was performed while in the second eye two-thirds of the corneal transplant adjacent to the transplanted limbal area remained clear 12 years after the limbo-corneal transplant. In the second patient, 1 eye showed no signs of recurrence 5 years after limbo-keratoplasty, whereas a recurrence of granular corneal deposits occurred 18 months after surgery in the fellow eye.These cases show that the simultaneous transplantation of healthy donor limbus when performing penetrating keratoplasty may prolong recurrence in granular corneal dystrophy. Although we were unable to prove it on the molecular level, these clinical courses may support the hypothesis that a limbal transplant helps prevent a recurrence.

Instrumented indentation for determination of mechanical properties of human cornea after ultraviolet-A crosslinking: MECHANICAL PROPERTIES OF HUMAN CORNEA

UVA crosslinking is used for treatment of corneal diseases such as keratoconus in order to stabilize the corneal tissue by crosslinking of the collagen fibers. It has been shown that the crosslinking treatment leads to a stiffening of the central corneal tissue. However, knowledge of lateral extent of the corneal stiffening as well as a systematic study of the mechanical response of human cornea is still missing. In our study we measured the stiffness (elastic modulus) of the anterior surface of healthy and crosslinked human corneas by instrumented indentation using a spherical indenter. The results show that the stiffness of the central and paracentral cornea increased almost two times after the crosslinking but the stiffening effect rapidly decreased towards the periphery of the radiation field. These new insights into the understanding of the biomechanical response of corneal crosslinking shall contribute to a better understanding and an optimization of this perspective medical treatment.

Connection of histological corneal endothelial cell count with endothelial cell density before penetrating keratoplasty

PurposeCorneal endothelial cell density and the integrity of the monolayer are essential for maintenance of a clear cornea. In 1992, Williams et al. introduced a method to estimate the endothelial cell density in histopathologic examination. It would enable an evaluation of the corneal host endothelium, even if preoperative measurement was not possible. The goal of this study is to evaluate the accuracy of the Williams equation in corneal buttons obtained from penetrating keratoplasties.MethodsHigh power field (HPF) photographs and histological endothelial cell counts were made from the corneal endothelial cells of each corneal histopathological cross-section. We then compared the calculated endothelial cell density using the Williams equation with the preoperative measured endothelial cell density. A bivariate regression analysis of the histological HPF cell counts and the preoperative endothelial cell density count was also performed.ResultsThe equation of Williams et al. overestimates the endothelial density in all of our patients. Linear regression showed a strong relation between the central histological HPF count and the preoperative endothelial cell density. The regression formula for the endothelial cell density is 59.66 + (272.447 × HPF count); p < 0.001, R2 = 0.901.ConclusionThis study confirms the relation between the corneal endothelial cell density, measured with specular microscopy, and the histopathological endothelial cell count in a HPF. However, the equation of Williams et al. provides an overestimation of the endothelial cell density. To proper utilize the histopathological endothelial cell count, a calibration of the equation coefficients in the local setting is necessary to prevent systematic errors.

Epithelinvasion nach traumatischer Flap-Dislokation

Eine traumatische Flap-Dislokation gehört zu den seltenen und späten Komplikationen nach LASIK [1]. Nach einer FlapDislokation kann es zu Irregularitäten der Hornhaut, Infektionen oder auch einer Epithelinvasion kommen [2,3]. Auch Fremdkörper sind im Interface beschrieben. Die Behandlung einer Epithelinvasion erfordert ein Anheben des Flaps, das Entfernen des eingewachsenen Epithels und ggf. die Behandlung mit proliferationshemmenden Medikamenten [2,4]. Wir präsentieren den Fall einer Patientin mit Epithelinvasion nach traumatischer Flap-Dislokation mit Foto-, OCTund histologischer Dokumentation.