Retinopathy in diabetic patients evaluated at a primary care clinic in Cape Town

Please cite as follows: Read, O. & Cook, C. 2007. Retinopathy in diabetic patients evaluated at a primary care clinic in Cape Town. South African Medical Journal, 97(10):941-945.The original publication is available at http://www.samj.org.zaDiabetic retinopathy is the fifth leading cause of global blindness, affecting an estimated 1.8 billion people and responsible for 4.8% of blindness.1 In South Africa, it is the third leading cause of blindness after cataract and glaucoma, and is responsible for 5% of blindness (0.04% of the total population). Cataract and refractive error are prioritised for the first phase of Vision 2020 in South Africa, while strategies to deal with diabetic retinopathy are recommended as a priority for the second phase.2 These strategies will include provision of adequate screening and argon laser treatment. The prevalence of diabetes differs in different population groups in South Africa. Among black and coloured South Africans, diabetes has risen from 3% to 12% over the past 10 years. Overall, the prevalence is conservatively estimated to be 3 - 5% (30 000 - 50 000 per million population).2 The prevalence of retinopathy in people with diabetes is estimated to be 20% (6 000 - 10 000 per million population), and the prevalence of blindness among these is estimated to be 5% (300 - 500 blind per million population).2 The objective of this study was to evaluate the retinopathy status of patients with diabetes seen at a primary care clinic in Cape Town and to assess the adequacy of the current diabetic screening programmes.Publishers versio

Development and Persistence of 'Static' or 'Dead' Zones in Flows

Certain ceramic products are formed through extrusion processes, where a slurry is forced through small openings to form such products as filters. At the top is a large tank. The slurry is forced through the tank into an extrusion chamber, and then out through slots to form the finished product. [The slurry may be thought of as a mixture of clay (or other polymers), water, and other binders. There are many ways to model this mixture, some of which will be discussed in this report. For instance, the slurry can be modeled as a non-Newtonian fluid, a two-phase flow with liquid and solids, or a viscoelastic fluid. One can also model the mixture as an elongated particle suspension in water, where changes in the orientation of the particles could affect the flow.] After the extrusion process is complete, one finds that ‘dead zones’ of dry paste accumulate in two areas. Most prominently, they occur at the lower corners of the tank. They also occur on the floor of the extrusion chamber near the slots, both near and away from the walls. Since we will consider wall effects in the tank, for the extrusion chamber we consider only flow cells sufficiently far away from the walls. Then we may exploit the periodic nature of the device and consider only a single flow cell. The aim of this project is to determine the formation mechanisms of these dead zones, and see how they affect the overall flow

The Large Synoptic Survey Telescope as a Near-Earth Object Discovery Machine

Using the most recent prototypes, design, and as-built system information, we test and quantify the capability of the Large Synoptic Survey Telescope (LSST) to discover Potentially Hazardous Asteroids (PHAs) and Near-Earth Objects (NEOs). We empirically estimate an expected upper limit to the false detection rate in LSST image differencing, using measurements on DECam data and prototype LSST software and find it to be about $450$~deg$^{-2}$. We show that this rate is already tractable with current prototype of the LSST Moving Object Processing System (MOPS) by processing a 30-day simulation consistent with measured false detection rates. We proceed to evaluate the performance of the LSST baseline survey strategy for PHAs and NEOs using a high-fidelity simulated survey pointing history. We find that LSST alone, using its baseline survey strategy, will detect $66\%$ of the PHA and $61\%$ of the NEO population objects brighter than $H=22$, with the uncertainty in the estimate of $\pm5$ percentage points. By generating and examining variations on the baseline survey strategy, we show it is possible to further improve the discovery yields. In particular, we find that extending the LSST survey by two additional years and doubling the MOPS search window increases the completeness for PHAs to $86\%$ (including those discovered by contemporaneous surveys) without jeopardizing other LSST science goals ($77\%$ for NEOs). This equates to reducing the undiscovered population of PHAs by additional $26\%$ ($15\%$ for NEOs), relative to the baseline survey.Comment: 66 pages, 18 figures, accepted to Icaru

"Any lady can do this without much trouble ...": class and gender in The dining room (1878)

Macmillan's "Art at Home" series (1876–83) was a collection of domestic advice manuals. Mentioned in every study of the late-nineteenth-century domestic interior, they have often been interpreted, alongside contemporary publications such as Charles Eastlake's Hints on Household Taste (1868), as indicators of late 1870s home furnishing styles. Mrs Loftie's The Dining Room (1878) was the series' fifth book and it considers one of the home's principal (and traditionally masculine) domestic spaces. Recent research on middle-class cultural practices surrounding food has placed The Dining Room within the tradition of Mrs Beeton's Household Management (1861); however, it is not a cookery book and hardly mentions dinners. Drawing upon unpublished archival sources, this paper charts the production and reception of The Dining Room, aiming to unravel its relationships with other contemporary texts and to highlight the difficulties of using it as historical evidence. While it offers fascinating insights into contemporary taste, class and gender, this paper suggests that, as an example of domestic design advice literature, it reveals far more about the often expedient world of nineteenth-century publishing practices

Increased ocular lens density in HIV-infected individuals with low nadir CD4 counts in South Africa: evidence of accelerated aging.

BACKGROUND: HIV infection is thought to be associated with an increased risk of age-related morbidity and premature aging. Lens density increases with age and may function as a biomarker of aging. The relationship of lens density measurements with clinical and demographic characteristics in HIV-infected individuals in comparison with a matched population of HIV-seronegative individuals was investigated. METHODS: Case-control study of 490 adults aged greater than or equal to 30 years composed of 242 HIV-infected adults and 248 age- and sex-matched HIV-seronegative individuals. Lens density was assessed using lens densitometry (Pentacam) imaging. Measurements were divided into quartiles, and comparison of HIV status and HIV-related factors was assessed by multivariate and multinomial logistic regression. RESULTS: The mean age was 41.2 years in HIV-infected adults and 42.3 years in HIV-seronegative individuals (P = 0.14). Of the HIV-infected adults, 88% were receiving antiretroviral therapy (ART) (median duration, 58 months), and within this group, their median CD4 count was 468 cells per microliter and 84% had undetectable viral load. Although adjusted lens densities were similar by HIV serostatus, participants on ART and who had nadir CD4 counts less than 200 cells per microliter had a higher risk of high lens density compared with HIV-seronegative individuals (P trend = 0.04). Lens density was weakly associated with detectable HIV viremia despite ART, but not with current CD4 count. CONCLUSIONS: HIV-infected individuals on ART with nadir CD4 counts <200 cells per microliter had increased risk of higher lens density. Lens density may represent a novel biomarker of aging, providing insight into accelerated aging trajectories in HIV infection

Factors affecting cataract surgical coverage and outcomes: a retrospective cross-sectional study of eye health systems in sub-Saharan Africa.

BACKGROUND: Recently there has been a great deal of new population based evidence on visual impairment generated in sub-Saharan Africa (SSA), thanks to the Rapid Assessment of Avoidable Blindness (RAAB) survey methodology. The survey provides information on the magnitude and causes of visual impairment for planning services and measuring their impact on eye health in administrative "districts" of 0.5-5 million people. The survey results describing the quantity and quality of cataract surgeries vary widely between study sites, often with no obvious explanation. The purpose of this study was to examine health system characteristics that may be associated with cataract surgical coverage and outcomes in SSA in order to better understand the determinants of reducing the burden of avoidable blindness due to cataract. METHODS: This was a descriptive study using secondary and primary data. The outcome variables were collected from existing surveys. Data on potential district level predictor variables were collected through a semi-structured tool using routine data and key informants where appropriate. Once collected the data were coded and analysed using statistical methods including t-tests, ANOVA and the Kruskal-Wallis analysis of variance test. RESULTS: Higher cataract surgical coverage was positively associated with having at least one fixed surgical facility in the area; availability of a dedicated operating theatre; the number of surgeons per million population; and having an eye department manager in the facility. Variables that were associated with better outcomes included having biometry and having an eye department manager in the facility. CONCLUSIONS: There are a number of health system factors at the district level that seem to be associated with both cataract surgical coverage and post-operative visual acuity outcomes. This study highlights the needs for better indicators and tools by which to measure and monitor the performance of eye health systems at the district level. It is unlikely that epidemiological data alone is sufficient for planning eye health services within a district and health managers and study coordinators need to consider collecting supplementary information in order to ensure appropriate planning can take place

Oxygen environment and islet size are the primary limiting factors of isolated pancreatic islet survival

Background: Type 1 diabetes is an autoimmune disease that destroys insulin-producing beta cells in the pancreas. Pancreatic islet transplantation could be an effective treatment option for type 1 diabetes once several issues are resolved, including donor shortage, prevention of islet necrosis and loss in pre- and post-transplantation, and optimization of immunosuppression. This study seeks to determine the cause of necrotic loss of isolated islets to improve transplant efficiency. Methodology: The oxygen tension inside isolated human islets of different sizes was simulated under varying oxygen environments using a computational in silico model. In vitro human islet viability was also assessed after culturing in different oxygen conditions. Correlation between simulation data and experimentally measured islet viability was examined. Using these in vitro viability data of human islets, the effect of islet diameter and oxygen tension of the culture environment on islet viability was also analyzed using a logistic regression model. Principal findings: Computational simulation clearly revealed the oxygen gradient inside the islet structure. We found that oxygen tension in the islet core was greatly lower (hypoxic) than that on the islet surface due to the oxygen consumption by the cells. The hypoxic core was expanded in the larger islets or in lower oxygen cultures. These findings were consistent with results from in vitro islet viability assays that measured central necrosis in the islet core, indicating that hypoxia is one of the major causes of central necrosis. The logistic regression analysis revealed a negative effect of large islet and low oxygen culture on islet survival. Conclusions/Significance: Hypoxic core conditions, induced by the oxygen gradient inside islets, contribute to the development of central necrosis of human isolated islets. Supplying sufficient oxygen during culture could be an effective and reasonable method to maintain isolated islets viable