Temporal scale of habitat selection for large carnivores: Balancing energetics, risk and finding prey.

When navigating heterogeneous landscapes, large carnivores must balance trade-offs between multiple goals, including minimizing energetic expenditure, maintaining access to hunting opportunities and avoiding potential risk from humans. The relative importance of these goals in driving carnivore movement likely changes across temporal scales, but our understanding of these dynamics remains limited. Here we quantified how drivers of movement and habitat selection changed with temporal grain for two large carnivore species living in human-dominated landscapes, providing insights into commonalities in carnivore movement strategies across regions. We used high-resolution GPS collar data and integrated step selection analyses to model movement and habitat selection for African lions Panthera leo in Laikipia, Kenya and pumas Puma concolor in the Santa Cruz Mountains of California across eight temporal grains, ranging from 5 min to 12 hr. Analyses considered landscape covariates that are related to energetics, resource acquisition and anthropogenic risk. For both species, topographic slope, which strongly influences energetic expenditure, drove habitat selection and movement patterns over fine temporal grains but was less important at longer temporal grains. In contrast, avoiding anthropogenic risk during the day, when risk was highest, was consistently important across grains, but the degree to which carnivores relaxed this avoidance at night was strongest for longer term movements. Lions and pumas modified their movement behaviour differently in response to anthropogenic features: lions sped up while near humans at fine temporal grains, while pumas slowed down in more developed areas at coarse temporal grains. Finally, pumas experienced a trade-off between energetically efficient movement and avoiding anthropogenic risk. Temporal grain is an important methodological consideration in habitat selection analyses, as drivers of both movement and habitat selection changed across temporal grain. Additionally, grain-dependent patterns can reflect meaningful behavioural processes, including how fitness-relevant goals influence behaviour over different periods of time. In applying multi-scale analysis to fine-resolution data, we showed that two large carnivore species in very different human-dominated landscapes balanced competing energetic and safety demands in largely similar ways. These commonalities suggest general strategies of landscape use across large carnivore species.

Conservation and monitoring of a persecuted African lion population by Maasai warriors.

Although Africa has many threatened species and biological hot spots, there are few citizen science schemes, particularly in rural communities, and there has been limited evaluation of existing programs. We engaged traditional Maasai warriors (pastoralist men aged 15 to 35) in community-based conservation and demographic monitoring of a persecuted African lion (Panthera leo) population. Through direct engagement, we investigated whether a citizen science approach employing local warriors, who had no formal education, could produce reliable data on the demographics, predation, and movements of a species with which their communities have been in conflict for generations. Warriors were given benefits such as literacy training and skill enhancement and engaged in the monitoring of the lions. The trained warriors reported on lion sign across an area nearly 4000 km(2) . Scientists worked together with the warriors to verify their reports and gather observations on the lion population. Using the verified reports and collected observations, we examined our scientific knowledge relative to the lion population preceding and during the citizen science program. Our observations showed that data quality and quantity improved with the involvement and training of the participants. Furthermore, because they engaged in conservation and gained personal benefits, the participants came to appreciate a species that was traditionally their foe. We believe engaging other local communities in biodiversity conservation and monitoring may be an effective conservation approach in rural Africa.

Association of Childhood Complex Trauma and Dissociation With Complex Posttraumatic Stress Disorder Symptoms in Adulthood.

This study replicates and extends prior research on the relationship of childhood complex trauma (CCT) and complex posttraumatic stress disorder (cPTSD) in adulthood, examining the role of psychoform and somatoform dissociation as a potential mediator. CCT, dissociation, and cPTSD were assessed in a large sample of adult psychiatric inpatients. Almost two thirds of participants reported having experienced CCT. Path analyses with bootstrap confidence intervals demonstrated a relationship between CCT, psychoform (but not somatoform) dissociation, and cPTSD. In addition, psychoform dissociation partially mediated the relationship between CCT and adult cPTSD symptoms. Dissociation (pathological or nonpathological psychoform and somatoform symptoms) warrants further clinical and scientific study as a potential link between CCT and the presence of adult cPTSD symptoms and/or the dissociative subtype of PTSD.

Efficacy of two lion conservation programs in Maasailand, Kenya.

Lion (Panthera leo) populations are in decline throughout most of Africa. The problem is particularly acute in southern Kenya, where Maasai pastoralists have been spearing and poisoning lions at a rate that will ensure near term local extinction. We investigated 2 approaches for improving local tolerance of lions: compensation payments for livestock lost to predators and Lion Guardians, which draws on local cultural values and knowledge to mitigate livestock-carnivore conflict and monitor carnivores. To gauge the overall influence of conservation intervention, we combined both programs into a single conservation treatment variable. Using 8 years of lion killing data, we applied Manski's partial identification approach with bounded assumptions to investigate the effect of conservation treatment on lion killing in 4 contiguous areas. In 3 of the areas, conservation treatment was positively associated with a reduction in lion killing. We then applied a generalized linear model to assess the relative efficacy of the 2 interventions. The model estimated that compensation resulted in an 87-91% drop in the number of lions killed, whereas Lion Guardians (operating in combination with compensation and alone) resulted in a 99% drop in lion killing.

Nationwide epidemiological approach to identify associations between keratoconus and immune-mediated diseases.

BACKGROUND: The aetiology of keratoconus (KC) remains poorly understood. KC has typically been described as a non-inflammatory disorder of the cornea. Nonetheless, there is increasing presumptive evidence for the role of the immune system in the pathogenesis of KC. AIM: To evaluate the association between KC and immune-mediated diseases on a population level. We hypothesise that KC is immune-mediated rather than a predominantly degenerative disease. METHODS: Data were obtained from the largest health insurance provider in the Netherlands. Dutch residents are obligatorily insured. The data contained all medical claims and sociodemographic characteristics from all KC patients plus all those data from a 1:6 age-matched and sex-matched control group. The primary outcome was the association between KC and immune-mediated diseases, as assessed by conditional logistic regression. RESULTS: Based on our analysis of 2051 KC cases and 12 306 matched controls, we identified novel associations between KC and Hashimoto's thyroiditis (OR=2.89; 95% CI: 1.41 to 5.94) and inflammatory skin conditions (OR=2.20; 95% CI: 1.37 to 3.53). We confirmed known associations between KC and atopic conditions, including allergic rash (OR=3.00; 95% CI: 1.03 to 8.79), asthma and bronchial hyperresponsiveness (OR=2.51; 95% CI: 1.63 to 3.84), and allergic rhinitis (OR=2.20; 95% CI: 1.39 to 3.49). CONCLUSION: Keratoconus appears positively associated with multiple immune-mediated diseases, which provides a population-based argument that systemic inflammatory responses may influence its onset. The identification of these particular diseases might shed light on potential comparable pathways through which this proinflammatory state is achieved, paving the way for pharmacological treatment strategies.

The evolutionary dynamics of the lion Panthera leo revealed by host and viral population genomics.

The lion Panthera leo is one of the world's most charismatic carnivores and is one of Africa's key predators. Here, we used a large dataset from 357 lions comprehending 1.13 megabases of sequence data and genotypes from 22 microsatellite loci to characterize its recent evolutionary history. Patterns of molecular genetic variation in multiple maternal (mtDNA), paternal (Y-chromosome), and biparental nuclear (nDNA) genetic markers were compared with patterns of sequence and subtype variation of the lion feline immunodeficiency virus (FIV(Ple)), a lentivirus analogous to human immunodeficiency virus (HIV). In spite of the ability of lions to disperse long distances, patterns of lion genetic diversity suggest substantial population subdivision (mtDNA Phi(ST) = 0.92; nDNA F(ST) = 0.18), and reduced gene flow, which, along with large differences in sero-prevalence of six distinct FIV(Ple) subtypes among lion populations, refute the hypothesis that African lions consist of a single panmictic population. Our results suggest that extant lion populations derive from several Pleistocene refugia in East and Southern Africa ( approximately 324,000-169,000 years ago), which expanded during the Late Pleistocene ( approximately 100,000 years ago) into Central and North Africa and into Asia. During the Pleistocene/Holocene transition ( approximately 14,000-7,000 years), another expansion occurred from southern refugia northwards towards East Africa, causing population interbreeding. In particular, lion and FIV(Ple) variation affirms that the large, well-studied lion population occupying the greater Serengeti Ecosystem is derived from three distinct populations that admixed recently.

Prevalence of Potentially Traumatic Events, Other Life Events and Subsequent Reactions Indicative for Posttraumatic Stress Disorder in the Netherlands: A General Population Study Based on the Trauma Screening Questionnaire.

The 12-month and lifetime prevalence of posttraumatic stress disorder (PTSD) in different country populations has been assessed while using clinical interviews. Because this methodology is relatively time-consuming and resource-intensive, disaster health researchers adopted instruments, like the Trauma Screening Questionnaire (TSQ). This study (1) used the TSQ to estimate the lifetime prevalence of potentially traumatic events and other life events (PTE/OLEs) and the one-week prevalence of subsequent reactions indicative for PTSD (based on DSM-IV PTSD criteria) in The Netherlands and (2) investigated risk and protective factors for the development of PTSD to overcome the lack of baseline comparison data on general populations and subgroups. The data were derived from the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2), a representative study in the Dutch general population aged 18 to 64 years (N = 6646), using face-to-face interviews. Logistic regression modeling was used to assess PTSD correlates. The lifetime PTE/OLE prevalence was 71.1%. Among exposed subjects, one-week PTSD prevalence was estimated at 2.0%. The correlates of PTSD were female gender, Moroccan, or Turkish ethnicity, and exposure to sexual abuse and exposure time less than four years ago. The results are discussed in relation to earlier 12-month and lifetime general population prevalence of PTSD in the Netherlands and other countries, and TSQ-based disaster studies. General population replications can provide additional TSQ baseline data, and shed light on exposure and PTSD prevalence assessed with different instruments.

Parameters Associated With Endothelial Cell Density Variability After Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To evaluate which parameters may affect endothelial cell loss after Descemet membrane endothelial keratoplasty (DMEK) by comparing eyes in the low vs high quartile of endothelial cell loss over a follow-up period of 4 years. DESIGN: Retrospective cohort study. METHODS: Donor endothelial cell density (ECD) decline was evaluated for 351 eyes of 275 patients up to 4 years after DMEK for Fuchs endothelial corneal dystrophy (FECD). Eyes with a postoperative endothelial cell loss in the lower quartile at all available follow-up moments were assigned to Group 1 (n = 51) and those in the upper quartile to Group 2 (n = 42). Multinomial regression was used to assess which covariates were related to greater ECD decline. RESULTS: Mean endothelial cell loss as compared to preoperative donor ECD for the entire study group was 33 (±16)%, 36 (±17)%, and 52 (±18)% at 1, 6, and 48 months postoperatively. Endothelial cell loss of Group 1 was 12 (±7)%, 13 (±6)%, and 26 (±8)% at, respectively, 1, 6, and 48 months postoperatively, and 59 (±10)%, 64 (±9)%, and 75 (±5)% in Group 2. Partial graft detachment, donor death cause cardiovascular/stroke (vs cancer), postoperative complications other than graft detachment, and severity of preoperative FECD (all P < .01) showed the strongest relation with greater ECD decline. CONCLUSIONS: DMEK eyes with a completely attached graft and operated in an early stage of FECD may show the lowest endothelial cell loss postoperatively.

Behavior-specific habitat selection by African lions may promote their persistence in a human-dominated landscape.

Co-occurrence with humans presents substantial risks for large carnivores, yet human-dominated landscapes are increasingly crucial to carnivore conservation as human land use continues to encroach on wildlife habitat. Flexibility in large carnivore behavior may be a primary factor mediating coexistence with people, allowing carnivores to calibrate their activity and habitat use to the perceived level of human risk. However, our understanding of how large carnivores adjust the timing and location of behaviors in response to variations in human activity across the landscape remains limited, impacting our ability to identify important habitat for populations outside of protected areas. Here we examine whether African lions (Panthera leo) modify their behavior and habitat use in response to risk of a human encounter, and whether behavior-specific habitat selection allows lions to access feeding opportunities in a human-dominated landscape in Kenya. We determined fine-scale behavioral states for lions using high-resolution GPS and accelerometer data, and then investigated behavior-specific habitat selection at multiple temporal and spatial scales (ranging from 15 minutes to 12 hours and from approximately 200 meters to several kilometers). We found that lions exhibit substantial differences in habitat selection with respect to humans based on behavioral state and time of day. During the day, when risk of human encounter is highest, lions avoided areas of high human use when resting, meandering, and feeding. However, lions specifically selected for habitat near people when feeding at night. Flexible habitat use by lions thus permits access to prey, which appear to concentrate in areas near humans. The importance of habitat near people for feeding was only apparent when analyses explicitly accounted for lion behavioral state and spatiotemporal scale, highlighting the necessity of incorporating such information when investigating human impacts on large carnivore habitat use. Our results support the contention that behavior-specific habitat selection promotes carnivore persistence in human-dominated landscapes, demonstrating the importance of considering not just whether but how large carnivores use habitat near humans when managing vulnerable populations.

Feature selection in feature network models: finding predictive subsets of features with the Positive Lasso.

A set of features is the basis for the network representation of proximity data achieved by feature network models (FNMs). Features are binary variables that characterize the objects in an experiment, with some measure of proximity as response variable. Sometimes features are provided by theory and play an important role in the construction of the experimental conditions. In some research settings, the features are not known a priori. This paper shows how to generate features in this situation and how to select an adequate subset of features that takes into account a good compromise between model fit and model complexity, using a new version of least angle regression that restricts coefficients to be non-negative, called the Positive Lasso. It will be shown that features can be generated efficiently with Gray codes that are naturally linked to the FNMs. The model selection strategy makes use of the fact that FNM can be considered as univariate multiple regression model. A simulation study shows that the proposed strategy leads to satisfactory results if the number of objects is less than or equal to 22. If the number of objects is larger than 22, the number of features selected by our method exceeds the true number of features in some conditions.

Resolving a conservation dilemma: Vulnerable lions eating endangered zebras.

When predators are removed or suppressed for generations, prey populations tend to increase and when predators are re-introduced, prey densities should fall back to pre-control levels. In cases of apparent competition where there are alternate abundant and rare prey species, rare species may decline further than expected or disappear altogether. Recently, concern about the impact of recovering predator populations on wildlife in Laikipia County, Kenya, has led to questions of whether lions (Panthera leo, IUCN Red List Vulnerable) exert top-down pressure on Grevy's zebra (Equus grevyi, IUCN Red List Endangered). We examined effects of lion predation on Plain's zebra (E. quagga, IUCN Red List Near Threatened) and Grevy's zebra populations in a 2,105 km2 area defined by lion movements. We used line transect surveys to estimate density of Grevy's (0.71/km2) and Plain's (15.9/km2) zebras, and satellite telemetry to measure movements for lions and both zebras. We tracked lions to potential feeding sites to estimate predation rates on zebras. We compared field-based estimates of predation rates on both zebras to random gas models of encounters that result in predation to ask if lions prey preferentially on Grevy's zebra at a sufficient rate to drive population declines. Lions preyed on Grevy's zebra significantly less than expected in 15 of 16 (94%) scenarios considered and lions preyed on Plain's zebras as expected or significantly less than expected in 15 of 16 scenarios. Population trend of Grevy's zebra indicates that the Kenya population may be stabilizing. Recruitment rate to the population has tripled since 2004, making it unlikely that lions are having an impact on Grevy's zebras. In Laikipia County, competitive displacement by livestock (Livestock: Grevy's zebra ratio = 864:1) and interference competition for grass with Plain's zebra (Plain's zebra:Grevy's zebra ratio = 22:1) are most likely the predominant threats to Grevy's Zebra recovery.

Estimating standard errors in feature network models.

Feature network models are graphical structures that represent proximity data in a discrete space while using the same formalism that is the basis of least squares methods employed in multidimensional scaling. Existing methods to derive a network model from empirical data only give the best-fitting network and yield no standard errors for the parameter estimates. The additivity properties of networks make it possible to consider the model as a univariate (multiple) linear regression problem with positivity restrictions on the parameters. In the present study, both theoretical and empirical standard errors are obtained for the constrained regression parameters of a network model with known features. The performance of both types of standard error is evaluated using Monte Carlo techniques.

From Attitudes to Actions: Predictors of Lion Killing by Maasai Warriors.

Despite legal protection, deliberate killing by local people is one of the major threats to the conservation of lions and other large carnivores in Africa. Addressing this problem poses particular challenges, mainly because it is difficult to uncover illicit behavior. This article examined two groups of Maasai warriors: individuals who have killed African lions (Panthera leo) and those who have not. We conducted interviews to explore the relationship between attitudes, intentions and known lion killing behavior. Factor analysis and logistic regression revealed that lion killing was mainly determined by: (a) general attitudes toward lions, (b) engagement in traditional customs, (c) lion killing intentions to defend property, and (d) socio-cultural killing intentions. Our results indicated that general attitudes toward lions were the strongest predictor of lion killing behavior. Influencing attitudes to encourage pro-conservation behavior may help reduce killing.

Multicenter Study of 6-Month Clinical Outcomes After Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To report the 6-month clinical outcomes of a large cohort of Descemet membrane endothelial keratoplasty (DMEK) eyes operated by 55 starting or experienced surgeons. METHODS: This is a retrospective, multicenter, interventional, cohort study with a total of 2485 eyes. Best-corrected visual acuity (BCVA), endothelial cell density (ECD) decrease, and intra- and post-operative complications were evaluated. Three groups based on case order were compared: group I (cases 1-24), group II (cases 25-99), and group III (cases ≥100). Forty-nine percent of the surgeons were in their learning curve (<25 cases), representing 10.4% of the surgeries. RESULTS: Six months after DMEK, BCVA improved in 90.5% of eyes, remained unchanged in 4.6%, and deteriorated in 4.9% (n = 1936); 75.4% of eyes reached a BCVA of ≥20/40 (≥0.5), 45.4% ≥20/25 (≥0.8), and 25.8% ≥20/20 (≥1.0) (n = 1959) and ECD decreased by 40% (±19) (n = 1272, P < 0.05). BCVA and ECD outcomes did not differ between groups I and III (P > 0.05). Intraoperative complications were reported for 9.4% of eyes, whereas graft detachment was the main postoperative complication (27.4%), with lower intra- and post-operative complication rates in group III than group I (P < 0.05). Rebubbling was performed in 20.1% of eyes; 13.8% required secondary keratoplasty within 6 months. CONCLUSIONS: DMEK is applicable for surgeons in various settings with good clinical outcomes. After an arbitrary learning curve (<25 cases), virtually all transplant-related complications declined with experience. Notably, surgeons with a higher annual caseload may pass faster through their learning curve than surgeons performing their first surgeries over an extended period.

Clinical Outcome of Rebubbling for Graft Detachment After Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To assess the clinical outcome after successful rebubbling procedures for visually significant graft detachment after Descemet membrane endothelial keratoplasty (DMEK). METHODS: From a total of 760 consecutive DMEK surgeries, 41 eyes required rebubbling. Of those, 33 eyes of 31 patients were successful and were included in our retrospective outcome analysis study. Main outcome measures were compared with those of matched controls with uneventful primary DMEK (attached DMEK grafts without rebubbling). Rebubbling was performed on average 25 (±20) days (range 7-91 days) after DMEK. All eyes were evaluated for best-corrected visual acuity, endothelial cell density (ECD), pachymetry, and complications up to 6 months after rebubbling. RESULTS: At 6 months after DMEK, best-corrected visual acuity in rebubbled eyes did not differ from that in control eyes (P = 0.514). The mean ECD decrease was higher in rebubbled than in control eyes (54% vs. 35%, respectively, P = 0.001). Pachymetry did not differ between both groups (P = 0.153). After rebubbling, one buphthalmic eye showed temporary intraocular pressure elevation and 5 eyes had minor graft edge detachment that did not require further treatment. CONCLUSIONS: Rebubbling for DMEK graft detachment may result in similar visual outcomes as in uncomplicated DMEK, when performed within the first 6 to 8 postoperative weeks. However, rebubbled eyes may have lower ECD, which may be attributed to additional air bubble trauma and/or selection bias through more extensive manipulation during initial DMEK or higher risk of graft detachment in more complicated eyes.

Two-Year Clinical Outcome of 500 Consecutive Cases Undergoing Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To evaluate the clinical outcome of 500 consecutive cases up to 2 years after Descemet membrane endothelial keratoplasty (DMEK) and to assess which parameters may have influenced the clinical outcome. METHODS: From a group of 500 eyes (393 patients), which underwent DMEK for Fuchs endothelial corneal dystrophy (FECD), bullous keratopathy, failed corneal transplants and other indications, clinical outcomes [best-corrected visual acuity (BCVA), central endothelial cell density (ECD), and central corneal thickness] were evaluated before, and at 6, 12, and 24 months after DMEK and postoperative complications were documented. RESULTS: At 12 months postoperatively, 81% of eyes reached a BCVA of ≥20/25 (≥0.8), 49% ≥20/20 (≥1.0), and 15% ≥20/18 (≥1.2) (n = 396) and remained stable up to 24 months (P = 0.828). Compared with preoperative ECD, mean postoperative ECD decreased by 37 (±18)%, 40 (±18)%, and 45 (±18)% at 6, 12, and 24 months, respectively (P < 0.05 for all time points). Surgery indication and graft attachment status were related to postoperative BCVA and ECD results. Eyes with FECD and attached grafts showed better BCVA outcomes and higher ECD (P < 0.05). Central corneal thickness decreased by 20 (±11)% to 525 (±46) µm from preoperative to 6 months postoperatively and remained stable thereafter (P > 0.05). Within the study period, retransplantation was required in 32 eyes (6.4%). Principal longer-term complications were secondary graft failure (1.4%) and allograft rejection (1.4%). CONCLUSIONS: Clinical outcomes remain excellent up to 2 years after DMEK, in particular for eyes operated on for FECD and with completely attached grafts.

Two-Year Refractive Outcomes After Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To monitor refractive changes after Descemet membrane endothelial keratoplasty (DMEK) and to determine what may influence these changes and the time point of stabilization. METHODS: From 67 pseudophakic DMEK eyes operated on for Fuchs endothelial dystrophy at a tertiary referral center, biomicroscopy, visual acuity, subjective refraction, and Scheimpflug-based corneal tomography data were obtained before and up to 2 years postoperatively. Visual acuity and changes in spherical equivalent (SE), mean anterior and posterior simulated keratometry (Km), and central pachymetry were analyzed. RESULTS: At 3 months postoperatively, both hyperopic (28/67 eyes) and myopic (21/67 eyes) shifts were observed; 18/67 eyes showed no SE change. The mean change in SE at 3 months was +0.33 diopters (D) (95% confidence interval = [0.11, 0.54], P = 0.028), which stabilized thereafter (P > 0.466). Initial flattening of mean anterior Km by 0.66D (95% confidence interval = [-0.81, -0.51], P < 0.001) at 3 months was followed by a slow steepening, which became significant between 1 and 2 years postoperatively (P < 0.001). Posterior Km stabilized after 3 months (P > 0.252). Preoperative to 3 months postoperative absolute changes in anterior Km were positively related to preoperative backscattered light from the central anterior cornea (P = 0.035), and the presence of partial graft detachment postoperatively (P = 0.013). CONCLUSIONS: After DMEK, SE and posterior corneal curvature were on average stable at 3 months after surgery, whereas the mean anterior corneal curvature showed an ongoing gradual change. Changes in anterior corneal curvature may be related to preoperative anterior corneal densitometry or postoperative partial graft detachment.

Association Between Graft Storage Time and Donor Age With Endothelial Cell Density and Graft Adherence After Descemet Membrane Endothelial Keratoplasty.

IMPORTANCE: After retrospectively evaluating the clinical outcome of 500 consecutive cases after Descemet membrane endothelial keratoplasty (DMEK), we extended the analysis in this study by assessing the effect of donor-related parameters on endothelial cell density (ECD) decline and detachment rate in this group. OBSERVATIONS: This retrospective case series included 500 cases who had undergone DMEK from October 2007 to September 2012 at the Netherlands Institute for Innovative Ocular Surgery (NIIOS), Rotterdam, the Netherlands. Logistic regression analysis (n = 332 eyes) showed that donor age might be associated with a 3% increase in the risk for a detachment (odds ratio, 0.97; 95% CI, 0.94-1.00; P = .049) (ie, higher donor age seems to be associated with lower chances of a detachment). In addition, linear regression analysis indicated that graft storage time in medium was associated with ECD decrease (ie, the longer the storage time, the larger the decrease at 6 months after DMEK) (P = .01). CONCLUSIONS AND RELEVANCE: We showed an association between graft storage time and ECD decline after DMEK and possibly between donor age and graft detachment. Therefore, donor storage times should be kept as short as possible to improve short-term ECDs. More research is needed to draw definite conclusions on the possible effect of donor age on the chance of a detachment after DMEK.

Endothelial Survival After Descemet Membrane Endothelial Keratoplasty: Effect of Surgical Indication and Graft Adherence Status.

IMPORTANCE: This study evaluates the longevity of Descemet membrane endothelial keratoplasty (DMEK) grafts in terms of endothelial survival and endothelial failure. OBJECTIVE: To determine endothelial survival and its association with the indication for surgery and/or partial graft detachment in DMEK. DESIGN, SETTING, AND PARTICIPANTS: Retrospective cross-sectional study of data collected from August 8, 2006, until June 17, 2015, at a tertiary referral center. A total of 352 eyes were evaluated up to 8 years after DMEK for Fuchs endothelial corneal dystrophy (FECD; n = 314), bullous keratopathy (BK; n = 31), and failed previous endothelial graft (n = 7), of which 314 eyes had complete graft attachment and 38 eyes had partial graft detachment (one-third of the graft surface area or less). Endothelial cell density was measured with specular microscopy, and Kaplan-Meier survival estimates were based on eyes with endothelial failure. Endothelial survival was followed up to 8 years after DMEK. MAIN OUTCOMES AND MEASURES: Endothelial cell density, endothelial failure, and endothelial survival. RESULTS: Endothelial cell density decreased to a mean (SD) of 952 (366) and 771 (321) cells/mm2 at 7 and 8 years postoperatively, respectively. Higher endothelial cell densities were found in eyes with FECD compared with those with BK (estimated mean difference, 261 cells/mm2; 95% CI, 118-404; P = .003) and in eyes with attached grafts compared with those with partially detached grafts (estimated mean difference, 330 cells/mm2; 95% CI, 208-452; P < .001), until 8 years. In 11 eyes (3.1%) that had concomitant ocular pathology, endothelial failure occurred within 4 years after DMEK. The overall graft survival probability was 0.96 at 5 and 8 years (95% CI, 0.94-0.99). At 8 years, better survival rates were found in eyes with FECD than in those with BK (survival probability, 0.97 [95% CI, 0.95-0.99] vs 0.84 [95% CI, 0.70-0.99], respectively); until the same follow-up, survival probabilities in eyes with attached and partially detached grafts were 0.97 (95% CI, 0.95-0.99) and 0.91 (95% CI, 0.82-0.99), respectively. CONCLUSIONS AND RELEVANCE: Endothelial decay was higher in eyes with a partial graft detachment than in those with attached grafts and lower in eyes with FECD than in those with BK. Endothelial failure only occurred in eyes with concomitant ocular pathology. These results suggest that eyes with DMEK that have undergone surgery for FECD with a completely attached graft may have an excellent prognosis.

Dual imputation model for incomplete longitudinal data.

Missing values are a practical issue in the analysis of longitudinal data. Multiple imputation (MI) is a well-known likelihood-based method that has optimal properties in terms of efficiency and consistency if the imputation model is correctly specified. Doubly robust (DR) weighing-based methods protect against misspecification bias if one of the models, but not necessarily both, for the data or the mechanism leading to missing data is correct. We propose a new imputation method that captures the simplicity of MI and protection from the DR method. This method integrates MI and DR to protect against misspecification of the imputation model under a missing at random assumption. Our method avoids analytical complications of missing data particularly in multivariate settings, and is easy to implement in standard statistical packages. Moreover, the proposed method works very well with an intermittent pattern of missingness when other DR methods can not be used. Simulation experiments show that the proposed approach achieves improved performance when one of the models is correct. The method is applied to data from the fireworks disaster study, a randomized clinical trial comparing therapies in disaster-exposed children. We conclude that the new method increases the robustness of imputations.