Quality of life and visual function in Nigeria: findings from the National Survey of Blindness and Visual Impairment

Aims To assess associations of visual function (VF) and quality of life (QOL) by visual acuity (VA), causes of blindness and types of cataract procedures in Nigeria. Methods Multi-stage stratified cluster random sampling was used to identify a nationally representative sample of persons aged >= 40 years. VF/QOL questionnaires were administered to participants with VA = 6/12. Results VF/QOL questionnaires were administered to 2076 participants. Spearman's rank correlation showed a strong correlation between decreasing VA and VF/QOL scores (p< 0.0001) with greatest impact on social (p< 0.0001) and mobility-related activities (p< 0.0001). People who were blind due to glaucoma had lower VF and QOL scores than those who were blind due to cataract. Mean VF and QOL scores were lower after couching compared with conventional cataract surgery (mean VF score=51.0 vs 63.0 and mean QOL score=71.3 vs 79.3). Finally, VF and QOL scores were lower among populations with specific characteristics. Conclusions Populations with the following characteristics should be targeted to improve VF and QOL: people who are blind, older people, women, manual labourers, people living in rural areas, those living in the northern geopolitical zones, those practising Islamic and Traditionalism faith, those not currently married and those who have undergone couching

Enhancement of Visual Field Predictions with Pointwise Exponential Regression (PER) and Pointwise Linear Regression (PLR).

PurposeThe study was conducted to evaluate threshold smoothing algorithms to enhance prediction of the rates of visual field (VF) worsening in glaucoma.MethodsWe studied 798 patients with primary open-angle glaucoma and 6 or more years of follow-up who underwent 8 or more VF examinations. Thresholds at each VF location for the first 4 years or first half of the follow-up time (whichever was greater) were smoothed with clusters defined by the nearest neighbor (NN), Garway-Heath, Glaucoma Hemifield Test (GHT), and weighting by the correlation of rates at all other VF locations. Thresholds were regressed with a pointwise exponential regression (PER) model and a pointwise linear regression (PLR) model. Smaller root mean square error (RMSE) values of the differences between the observed and the predicted thresholds at last two follow-ups indicated better model predictions.ResultsThe mean (SD) follow-up times for the smoothing and prediction phase were 5.3 (1.5) and 10.5 (3.9) years. The mean RMSE values for the PER and PLR models were unsmoothed data, 6.09 and 6.55; NN, 3.40 and 3.42; Garway-Heath, 3.47 and 3.48; GHT, 3.57 and 3.74; and correlation of rates, 3.59 and 3.64.ConclusionsSmoothed VF data predicted better than unsmoothed data. Nearest neighbor provided the best predictions; PER also predicted consistently more accurately than PLR. Smoothing algorithms should be used when forecasting VF results with PER or PLR.Translational relevanceThe application of smoothing algorithms on VF data can improve forecasting in VF points to assist in treatment decisions

Virological outcomes of second-line protease inhibitor-based treatment for human immunodeficiency virus type 1 in a high-prevalence rural South African setting: a competing-risks prospective cohort analysis

Background. Second-line antiretroviral therapy (ART) based on ritonavir-boosted protease inhibitors (bPIs) represents the only available option after first-line failure for the majority of individuals living with human immunodeficiency virus (HIV) worldwide. Maximizing their effectiveness is imperative. Methods. This cohort study was nested within the French National Agency for AIDS and Viral Hepatitis Research (ANRS) 12249 Treatment as Prevention (TasP) cluster-randomized trial in rural KwaZulu-Natal, South Africa. We prospectively investigated risk factors for virological failure (VF) of bPI-based ART in the combined study arms. VF was defined by a plasma viral load >1000 copies/mL ≥6 months after initiating bPI-based ART. Cumulative incidence of VF was estimated and competing risk regression was used to derive the subdistribution hazard ratio (SHR) of the associations between VF and patient clinical and demographic factors, taking into account death and loss to follow-up. Results. One hundred one participants contributed 178.7 person-years of follow-up. Sixty-five percent were female; the median age was 37.4 years. Second-line ART regimens were based on ritonavir-boosted lopinavir, combined with zidovudine or tenofovir plus lamivudine or emtricitabine. The incidence of VF on second-line ART was 12.9 per 100 person-years (n = 23), and prevalence of VF at censoring was 17.8%. Thirteen of these 23 (56.5%) virologic failures resuppressed after a median of 8.0 months (interquartile range, 2.8-16.8 months) in this setting where viral load monitoring was available. Tuberculosis treatment was associated with VF (SHR, 11.50 [95% confidence interval, 3.92-33.74]; P < .001). Conclusions. Second-line VF was frequent in this setting. Resuppression occurred in more than half of failures, highlighting the value of viral load monitoring of second-line ART. Tuberculosis was associated with VF; therefore, novel approaches to optimize the effectiveness of PI-based ART in high-tuberculosis-burden settings are needed

Improving the Convergence of Vector Fitting for Equivalent Circuit Extraction From Noisy Frequency Responses

The vector fitting (VF) algorithm has become a common tool in electromagnetic compatibility and signal integrity studies. This algorithm allows the derivation of a rational approximation to the transfer matrix of a given linear structure starting from measured or simulated frequency responses. This paper addresses the convergence properties of a VF when the frequency samples are affected by noise.We show that small amounts of noise can seriously impair or destroy convergence. This is due to the presence of spurious poles that appear during the iterations. To overcome this problem we suggest a simple modification of the basic VF algorithm, based on the identification and removal of the spurious poles. Also, an incremental pole addition and relocation process is proposed in order to provide automatic order estimation even in the presence of significant noise.We denote the resulting algorithm as vector fitting with adding and skimming (VF-AS). A thorough validation of the VF-AS algorithm is presented using a Monte Carlo analysis on synthetic noisy frequency responses. The results show excellent convergence and significant improvements with respect to the basic VF iteration scheme. Finally, we apply the new VF-AS algorithm to measured scattering responses of interconnect structures and networks typical of high-speed digital systems

Glaucomatous vertical vessel density asymmetry of the temporal raphe detected with optical coherence tomography angiography.

Changes in retinal vasculature and ocular circulation may play an important role in the glaucoma development and progression. We evaluated the vertical asymmetry across the temporal raphe of the deep retinal layer vessel density, using swept-source optical coherence tomography angiography (SS-OCTA), and its relationship with the central visual field (VF) loss. Thirty-four eyes of 27 patients with open-angle glaucoma were included. SS-OCTA macular scanning was performed within a 3 × 3 mm (300 × 300 pixels) volume, centred on the fovea. The relationships between the vertical asymmetrical deep retinal vessel density reduction (ADRVD) across the temporal raphe and various ocular parameters were analysed. Twenty-two glaucomatous eyes with ADRVDs had central VF loss. Contrarily, ADRVDs were not found in any of the 12 eyes without central VF loss. Thirteen eyes (59.1%) with central VF loss had ADRVDs topographically corresponding to the central VF loss and macular ganglion cell complex thinning. The glaucomatous eyes with ADRVDs exhibited inferior rather than superior central VF loss (P = 0.032). Thus, ADRVD specifically indicates the glaucomatous central visual loss. Further analysis of ADRVD may improve our understanding on glaucoma pathogenesis, offering new treatment insights

Resistance management in Vf apple scab resistant organic apple orchards

Modern Vf scab resistant apple varieties open the way for organic growers to lower fungicide input, higher yields, better skin quality, more biological control for mites and insect pests and better consumer acceptance of their management practices. Manny examples in the past years have shown however that the Vf resis-tance can be easily overcome by local scab populations in north-western Europe. Discussions during the meetings of the IOBC working group Diseases in Orchards in 2000 in Fontevraud (France) and in 2003 in Lindau (Germany) lead to a set of management practises necessary to prevent gene-fulx, and selection to-wards Vf virulence in the local apple scab populations. Eleven orchards of the Vf resistant apple variety Santana that where planted between 1998 and 2000 where monitored for apple scab lesions on fruits form 2002 to 2005. The results where evaluated in respect tot the applied resistance management practices. We conclude that fungicide treatments on the major primary scab infections are the key factor in the resistance management on Vf resistant apple varieties. From a practical viewpoint these early season fungicide applications are also necessary for the control of powdery mildew, as the main Vf- resistant apple cultivars appear to be relatively susceptible to powdery mildew. For private gardens apple varieties with field resistance to apple scab should be advised, not Vf resistant varieties

A comparative study of methods for estimating virtual flux at the point of common coupling in grid connected voltage source converters with LCL filter

Grid connected Voltage Source Converters (VSCs) with LCL filters usually have voltage measurements at the filter capacitors, while it can be important to control the active or reactive power injection at the grid-side of the LCL filter, for instance at a Point of Common Coupling (PCC). Synchronization to the PCC voltage can be obtained by Virtual Flux (VF) estimation, which can also allow for voltage sensor-less operation of VSCs. This paper is presenting a comparative evaluation of methods for estimating the VF at the PCC, considering a VSC connected to the grid through an LCL filter with a Proportional Resonant (PR) controller as the inner current control loop. The VF estimation is achieved by using frequency adaptive dual SOGI-QSGs (DSOGI-VF). The Frequency Locked Loop (FLL) is used in order to keep the positive and negative sequence (PNS) VF estimation inherently frequency adaptive. Three different methods are considered for obtaining the capacitor current needed for estimating the VF at the grid side of the LCL filter which are based on fully estimation by using the voltage sensor-less method, by estimating the capacitor current from the measured voltage or by using additional capacitor current sensors. The results have been compared and validated by simulation studies.Peer ReviewedPostprint (author's final draft

Evaluation of the progression of visual field damage in patients suffering from early manifest glaucoma

Abstract BACKGROUND: This retrospective study aimed to determine how often a perimetric examination should be carried out in order to identify visual field (VF) changes in patients with relatively early manifestation glaucoma. MATERIALS AND METHODS: Patients included had a relatively recent manifestation of primary open-angle glaucoma. Patients with a minimum follow-up of 5 years and a minimum of seven VF tests were included. Statistical analysis was performed to verify the trend of variations in mean defect (MD) over time (PeriData). The results were subjected to a t-test for a comparative analysis of progression of VF changes over time. The annual rate of progression provided by PeriData considering all the VFs analyzed was compared with that obtained on half of the VF examinations during the same follow-up period. An analysis of the MD trend over time was also carried out in relationship to the number of VF tests done and by dividing the sample into a high-frequency group (more than eight VFs) and a low-frequency group (fewer than eight VFs) in the follow-up period. RESULTS: A total of 96 eyes of 96 patients were included, and overall 846 VFs were examined. The paired t-test performed comparing the MD index of all the VFs against half of them did not show statistical significance (P=0.537). The high-frequency group comprised 39 eyes (average VF 11.05±1.91, average time interval 0.76 years) while the low-frequency group comprised 57 eyes (average VF 6.95±0.6, average time interval 1.21 years). The analysis of the MD trend in the high-frequency patients showed significance (P=0.017); the low-frequency group did not show statistical significance (P=0.08). CONCLUSION: The number of VFs in a determined time interval was not significant. However, a greater frequency of tests provides a predictive evaluation of the rate of progression of early manifestation open-angle glaucoma