Christine Schmucker

A paraxial schematic eye model for the growing C57BL/6 mouse

PURPOSE The mouse eye has potential to become an important model for studies on the genetic control of eye growth and myopia. However, no data are published on the development of its optical properties. We developed a paraxial schematic model of the growing eye for the most common laboratory mouse strain, the C57BL/6 mouse, for the age range between 22 and 100 days. METHODS Refractive development was followed with eccentric infrared photorefraction and corneal curvature with infrared photokeratometry. To measure ocular dimensions, freshly excised eyes were immediately frozen after enucleation to minimize distortions. Eyes were cut with a cryostat down to the bisecting horizontal plane, until the optic nerve head became visible. The standard deviations were +/-10 microm for repeated measurements in highly magnified videographs, taken in several section planes close to the equator in the same eyes. To evaluate inter-eye and inter-individual variability, a total of 20 mice (34 eyes) were studied, with 3-4 eyes for each of the 9 sampling ages. Schematic eye models were developed using paraxial ray tracing software (OSLO, LT Lambda Research Corporation, and a self-written program). RESULTS The measured refractive errors were initially +4.0+/-0.6 D at approximately 30 days, and levelled off with +7.0+/-2.5 D at about 70 days. Corneal radius of curvature did not change with age (1.414+/-0.019 mm). Both axial lens diameter and axial eye length grew linearly (regression equations: lens, 1619 microm +5.5 microm/day, R=0.916; axial length, 2899 microm +4.4 microm/day, R=0.936). The lens grew so fast that vitreous chamber depth declined with age (regression equation: 896 microm -3.2 microm/day, R=0.685). The radii of curvature of the anterior lens surface increased during development (from 0.982 mm at day 22 to 1.208 mm at day 100), whereas the radii of the posterior lens surface remained constant (-1.081+/-0.054 mm). The calculated homogeneous lens index increased linearly with age (from 1.568 to 1.605). The small eye artifact, calculated from the dioptric difference of the positions of the vitreo-retinal interface and the photoreceptor plane, increased from +35.2 to +39.1 D, which was much higher than the hyperopia measured with photorefraction. Retinal image magnification increased from 31 to 34 microm/deg, and the f/number remained < or =1 at all ages, suggesting a bright retinal image. A calculated axial eye elongation of 5.4-6.5 microm was sufficient to make the schematic eye 1 D more myopic. CONCLUSIONS The most striking features of the mouse eye were that linear growth was slow but extended far beyond sexual maturity, that the corneal curvature did not increase, and that the prominent lens growth caused a developmental decline of the vitreous chamber depth.

A Safety Review and Meta-Analyses of Bevacizumab and Ranibizumab: Off-Label versus Goldstandard

Background We set out a systemic review to evaluate whether off-label bevacizumab is as safe as licensed ranibizumab, and whether bevacizumab can be justifiably offered to patients as a treatment for age-related macular degeneration with robust evidence of no differential risk. Methods and Findings Medline, Embase and the Cochrane Library were searched with no limitations of language and year of publication. We included RCTs with a minimum follow-up of one year which investigated bevacizumab or ranibizumab in direct comparison or against any other control group (indirect comparison). Direct comparison (3 trials, 1333 patients): The one year data show a significantly higher rate of ocular adverse effects (AE) with bevacizumab compared to ranibizumab (RR = 2.8; 95% CI 1.2–6.5). The proportion of patients with serious infections and gastrointestinal disorders was also higher with bevacizumab than with ranibizumab (RR = 1.3; 95% CI 1.0–1.7). Arterial thromboembolic events were equally distributed among the groups. Indirect comparison: Ranibizumab versus any control (5 trials, 4054 patients): The two year results of three landmark trials showed that while absolute rates of serious ocular AE were low (≤2.1%), relative harm was significantly raised (RR = 3.1; 95% CI 1.1–8.9). A significant increase in nonocular haemorrhage was also observed with ranibizumab (RR = 1.7; 95% CI 1.1–2.7). Bevacizumab versus any control (3 trials, 244 patients): We were unable to judge the safety profile of bevacizumab due to the poor quality of AE monitoring and reporting in the trials. Conclusions Evidence from head-to-head trials raises concern about an increased risk of ocular and multiple systemic AE with bevacizumab. Therefore, clinicians and patients should continue to carefully weight up the benefits and harms when choosing between the two treatment options. We also emphasize the need for studies that are powered not just for efficacy, but for defined safety outcomes based on the signals detected in this systematic review.

Intravitreal bevacizumab (Avastin®) versus ranibizumab (Lucentis®) for the treatment of age-related macular degeneration: a safety review

Aim To conduct a systematic review in order to compare adverse effects (AE) and the reporting of harm in randomised controlled trials (RCTs) and non-RCTs evaluating intravitreal ranibizumab and bevacizumab in age-related macular degeneration. Methods Medline, Embase and the Cochrane Library were searched with no limitations of language and year of publication. Studies which compared bevacizumab or ranibizumab as monotherapy with any other control group were included. Case series were included if they met predefined quality standards. Results The 2 year results of phase III trials evaluating ranibizumab show that the rates of serious ocular AE were low (≤2.1%) but indicate major safety concerns (RR 3.13, 95% CI 1.10 to 8.92). A possible signal with regard to thromboembolic events (RR 1.35, 95% CI 0.66 to 2.77) and a significant increase in non-ocular haemorrhage (RR 1.62, 95% CI 1.03 to 2.55) were also noted. In contrast to ranibizumab trials, the RCTs evaluating bevacizumab are of limited value. The main shortcomings are small sample sizes and an apparent lack of rigorous monitoring for AE. A critical assessment of the large number of published case series evaluating bevacizumab also shows that no reliable conclusions on safety can be drawn using this study design. Therefore, any perception that intravitreal bevacizumab injections are not associated with major ocular or systemic AE are not supported by reliable data. Conclusion The bevacizumab studies show too many methodological limitations to rule out any major safety concerns. Higher evidence from ranibizumab trials suggests signals for an increased ocular and systemic vascular and haemorrhagic risk which warrants further investigation.

Extent of Non-Publication in Cohorts of Studies Approved by Research Ethics Committees or Included in Trial Registries

Background The synthesis of published research in systematic reviews is essential when providing evidence to inform clinical and health policy decision-making. However, the validity of systematic reviews is threatened if journal publications represent a biased selection of all studies that have been conducted (dissemination bias). To investigate the extent of dissemination bias we conducted a systematic review that determined the proportion of studies published as peer-reviewed journal articles and investigated factors associated with full publication in cohorts of studies (i) approved by research ethics committees (RECs) or (ii) included in trial registries. Methods and Findings Four bibliographic databases were searched for methodological research projects (MRPs) without limitations for publication year, language or study location. The searches were supplemented by handsearching the references of included MRPs. We estimated the proportion of studies published using prediction intervals (PI) and a random effects meta-analysis. Pooled odds ratios (OR) were used to express associations between study characteristics and journal publication. Seventeen MRPs (23 publications) evaluated cohorts of studies approved by RECs; the proportion of published studies had a PI between 22% and 72% and the weighted pooled proportion when combining estimates would be 46.2% (95% CI 40.2%–52.4%, I2 = 94.4%). Twenty-two MRPs (22 publications) evaluated cohorts of studies included in trial registries; the PI of the proportion published ranged from 13% to 90% and the weighted pooled proportion would be 54.2% (95% CI 42.0%–65.9%, I2 = 98.9%). REC-approved studies with statistically significant results (compared with those without statistically significant results) were more likely to be published (pooled OR 2.8; 95% CI 2.2–3.5). Phase-III trials were also more likely to be published than phase II trials (pooled OR 2.0; 95% CI 1.6–2.5). The probability of publication within two years after study completion ranged from 7% to 30%. Conclusions A substantial part of the studies approved by RECs or included in trial registries remains unpublished. Due to the large heterogeneity a prediction of the publication probability for a future study is very uncertain. Non-publication of research is not a random process, e.g., it is associated with the direction of study findings. Our findings suggest that the dissemination of research findings is biased.

Efficacy and safety of intravitreal therapy in macular edema due to branch and central retinal vein occlusion: a systematic review.

Background Intravitreal agents have replaced observation in macular edema in central (CRVO) and grid laser photocoagulation in branch retinal vein occlusion (BRVO). We conducted a systematic review to evaluate efficacy and safety outcomes of intravitreal therapies for macular edema in CRVO and BRVO. Methods And Findings: MEDLINE, Embase, and the Cochrane Library were systematically searched for RCTs with no limitations of language and year of publication. 11 RCTs investigating anti-VEGF agents (ranibizumab, bevacizumab, aflibercept) and steroids (triamcinolone, dexamethasone implant) with a minimum follow-up of 1 year were evaluated. Efficacy: CRVO Greatest gain in visual acuity after 12 months was observed both under aflibercept 2 mg: +16.2 letters (8.5 injections), and under bevacizumab 1.25 mg: +16.1 letters (8 injections). Ranibizumab 0.5 mg improved vision by +13.9 letters (8.8 injections). Triamcinolone 1 mg and 4 mg stabilized visual acuity at a lower injection frequency (-1.2 letters, 2 injections). BRVO Ranibizumab 0.5 mg resulted in a visual acuity gain of +18.3 letters (8.4 injections). The effect of dexamethasone implant was transient after 1.9 implants in both indications. Safety Serious ocular adverse events were rare, e.g., endophthalmitis occurred in 0.0-0.9%. Major differences were found in an indirect comparison between steroids and anti-VEGF agents for cataract progression (19.8-35.0% vs. 0.9-7.0%) and in required treatment of increased intraocular pressure (7.0-41.0% vs. none). No major differences were identified in systemic adverse events. Conclusions Anti-VEGF agents result in a promising gain of visual acuity, but require a high injection frequency. Dexamethasone implant might be an alternative, but comparison is impaired as the effect is temporary and it has not yet been tested in PRN regimen. The ocular risk profile seems to be favorable for anti-VEGF agents in comparison to steroids. Because comparative data from head-to-head trials are missing currently, clinicians and patients should carefully weigh the benefit-harm ratio.

Intravitreal bevacizumab (Avastin) vs. ranibizumab (Lucentis) for the treatment of age-related macular degeneration: a systematic review.

Purpose of review We conducted a systematic review to evaluate whether the existing evidence justifies the intravitreal use of bevacizumab in comparison to ranibizumab in age-related macular degeneration. Recent findings Compared with photodynamic therapy, bevacizumab shows a relative improvement in visual acuity that is of similar size as in the comparison of ranibizumab with photodynamic therapy (relative improvement from 30 to 35%). However, this finding is based on one randomized controlled trial including less than 50 patients treated with bevacizumab. Also, nothing is known about long-term (>12 months) improvements in visual acuity and optimal treatment intervals for bevacizumab. Regarding safety, the published literature indicates that ocular and systemic adverse effects are less frequent under bevacizumab than ranibizumab treatment. But the validity of this finding is strongly limited by inadequate reporting, an unsystematic evaluation of adverse effects and short follow-up times in studies evaluating bevacizumab. Summary Given the lack of controlled data, the widespread off-label use of bevacizumab is not justified in clinical practice. On the other hand, a major challenge in the management of patients who require repeated antivascular endothelial growth factor injections is the high cost of ranibizumab. This dilemma underlines the need for head-to-head studies comparing both vascular endothelial growth factor antibodies, or, at least, well conducted randomized controlled trials evaluating intravitreal bevacizumab.

Evidence-informed recommendations to reduce dissemination bias in clinical research: conclusions from the OPEN (Overcome failure to Publish nEgative fiNdings) project based on an international consensus meeting

Background Dissemination bias in clinical research severely impedes informed decision-making not only for healthcare professionals and patients, but also for funders, research ethics committees, regulatory bodies and other stakeholder groups that make health-related decisions. Decisions based on incomplete and biased evidence cannot only harm people, but may also have huge financial implications by wasting resources on ineffective or harmful diagnostic and therapeutic measures, and unnecessary research. Owing to involvement of multiple stakeholders, it remains easy for any single group to assign responsibility for resolving the problem to others. Objective To develop evidence-informed general and targeted recommendations addressing the various stakeholders involved in knowledge generation and dissemination to help overcome the problem of dissemination bias on the basis of previously collated evidence. Methods Based on findings from systematic reviews, document analyses and surveys, we developed general and targeted draft recommendations. During a 2-day workshop in summer 2013, these draft recommendations were discussed with external experts and key stakeholders, and refined following a rigorous and transparent methodological approach. Results Four general, overarching recommendations applicable to all or most stakeholder groups were formulated, addressing (1) awareness raising, (2) implementation of targeted recommendations, (3) trial registration and results posting, and (4) systematic approaches to evidence synthesis. These general recommendations are complemented and specified by 47 targeted recommendations tailored towards funding agencies, pharmaceutical and device companies, research institutions, researchers (systematic reviewers and trialists), research ethics committees, trial registries, journal editors and publishers, regulatory agencies, benefit (health technology) assessment institutions and legislators. Conclusions Despite various recent examples of dissemination bias and several initiatives to reduce it, the problem of dissemination bias has not been resolved. Tailored recommendations based on a comprehensive approach will hopefully help increase transparency in biomedical research by overcoming the failure to disseminate negative findings.

Effectiveness of screening preschool children for amblyopia: a systematic review

BackgroundAmblyopia and amblyogenic factors like strabismus and refractive errors are the most common vision disorders in children. Although different studies suggest that preschool vision screening is associated with a reduced prevalence rate of amblyopia, the value of these programmes is the subject of a continuing scientific and health policy discussion. Therefore, this systematic review focuses on the question of whether screening for amblyopia in children up to the age of six years leads to better vision outcomes.MethodsTen bibliographic databases were searched for randomised controlled trials, non-randomised controlled trials and cohort studies with no limitations to a specific year of publication and language. The searches were supplemented by handsearching the bibliographies of included studies and reviews to identify articles not captured through our main search strategy.ResultsFive studies met the inclusion criteria. Of these, three studies suggested that screening is associated with an absolute reduction in the prevalence of amblyopia between 0.9% and 1.6% (relative reduction: between 45% and 62%). However, the studies showed weaknesses, limiting the validity and reliability of their findings. The main limitation was that studies with significant results considered only a proportion of the originally recruited children in their analysis. On the other hand, retrospective sample size calculation indicated that the power based on the cohort size was not sufficient to detect small changes between the groups. Outcome parameters such as quality of life or adverse effects of screening have not been adequately investigated in the literature currently available.ConclusionPopulation based preschool vision screening programmes cannot be sufficiently assessed by the literature currently available. However, it is most likely that the present systematic review contains the most detailed description of the main limitations in current available literature evaluating these programmes. Therefore, future research work should be guided by the findings of this publication.

A protocol for a systematic review on the impact of unpublished studies and studies published in the gray literature in meta-analyses

AbstractBackgroundMeta-analyses are particularly vulnerable to the effects of publication bias. Despite methodologists’ best efforts to locate all evidence for a given topic the most comprehensive searches are likely to miss unpublished studies and studies that are published in the gray literature only. If the results of the missing studies differ systematically from the published ones, a meta-analysis will be biased with an inaccurate assessment of the intervention’s effects.As part of the OPEN project (http://www.open-project.eu) we will conduct a systematic review with the following objectives:▪ To assess the impact of studies that are not published or published in the gray literature on pooled effect estimates in meta-analyses (quantitative measure).▪ To assess whether the inclusion of unpublished studies or studies published in the gray literature leads to different conclusions in meta-analyses (qualitative measure).Methods/DesignInclusion criteria: Methodological research projects of a cohort of meta-analyses which compare the effect of the inclusion or exclusion of unpublished studies or studies published in the gray literature. Literature search: To identify relevant research projects we will conduct electronic searches in Medline, Embase and The Cochrane Library; check reference lists; and contact experts. Outcomes: 1) The extent to which the effect estimate in a meta-analyses changes with the inclusion or exclusion of studies that were not published or published in the gray literature; and 2) the extent to which the inclusion of unpublished studies impacts the meta-analyses’ conclusions. Data collection: Information will be collected on the area of health care; the number of meta-analyses included in the methodological research project; the number of studies included in the meta-analyses; the number of study participants; the number and type of unpublished studies; studies published in the gray literature and published studies; the sources used to retrieve studies that are unpublished, published in the gray literature, or commercially published; and the validity of the methodological research project. Data synthesis: Data synthesis will involve descriptive and statistical summaries of the findings of the included methodological research projects.DiscussionResults are expected to be publicly available in the middle of 2013.

Systematic review finds that study data not published in full text articles have unclear impact on meta-analyses results in medical research.

Background A meta-analysis as part of a systematic review aims to provide a thorough, comprehensive and unbiased statistical summary of data from the literature. However, relevant study results could be missing from a meta-analysis because of selective publication and inadequate dissemination. If missing outcome data differ systematically from published ones, a meta-analysis will be biased with an inaccurate assessment of the intervention effect. As part of the EU-funded OPEN project (www.open-project.eu) we conducted a systematic review that assessed whether the inclusion of data that were not published at all and/or published only in the grey literature influences pooled effect estimates in meta-analyses and leads to different interpretation. Methods and findings Systematic review of published literature (methodological research projects). Four bibliographic databases were searched up to February 2016 without restriction of publication year or language. Methodological research projects were considered eligible for inclusion if they reviewed a cohort of meta-analyses which (i) compared pooled effect estimates of meta-analyses of health care interventions according to publication status of data or (ii) examined whether the inclusion of unpublished or grey literature data impacts the result of a meta-analysis. Seven methodological research projects including 187 meta-analyses comparing pooled treatment effect estimates according to different publication status were identified. Two research projects showed that published data showed larger pooled treatment effects in favour of the intervention than unpublished or grey literature data (Ratio of ORs 1.15, 95% CI 1.04–1.28 and 1.34, 95% CI 1.09–1.66). In the remaining research projects pooled effect estimates and/or overall findings were not significantly changed by the inclusion of unpublished and/or grey literature data. The precision of the pooled estimate was increased with narrower 95% confidence interval. Conclusions Although we may anticipate that systematic reviews and meta-analyses not including unpublished or grey literature study results are likely to overestimate the treatment effects, current empirical research shows that this is only the case in a minority of reviews. Therefore, currently, a meta-analyst should particularly consider time, effort and costs when adding such data to their analysis. Future research is needed to identify which reviews may benefit most from including unpublished or grey data.