Prevalence and causes of blindness and visual impairment in Muyuka: a rural health district in South West Province, Cameroon.

AIM: To estimate the prevalence and causes of blindness and visual impairment in the population aged 40 years and over in Muyuka, a rural district in the South West Province of Cameroon. METHODS: A multistage cluster random sampling methodology was used to select 20 clusters of 100 people each. In each cluster households were randomly selected and all eligible people had their visual acuity (VA) measured by an ophthalmic nurse. Those with VA <6/18 were examined by an ophthalmologist. RESULTS: 1787 people were examined (response rate 89.3%). The prevalence of binocular blindness was 1.6% (95% CI: 0.8% to 2.4%), 2.2% (1.% to 3.1%) for binocular severe visual impairment, and 6.4% (5.0% to 7.8%) for binocular visual impairment. Cataract was the main cause of blindness (62.1%), severe visual impairment (65.0%), and visual impairment (40.0%). Refractive error was an important cause of severe visual impairment (15.0%) and visual impairment (22.5%). The cataract surgical coverage for people was 55% at the <3/60 level and 33% at the <6/60 level. 64.3% of eyes operated for cataract had poor visual outcome (presenting VA<6/60). CONCLUSIONS: Strategies should be developed to make cataract services affordable and accessible to the population in the rural areas. There is an urgent need to improve the outcome of cataract surgery. Refractive error services should be provided at the community level

Cataract prevalence, cataract surgical coverage and barriers to uptake of cataract surgical services in Pakistan: the Pakistan National Blindness and Visual Impairment Survey.

AIM: To estimate the prevalence of visual impairment and blindness caused by cataract, the prevalence of aphakia/pseudophakia, cataract surgical coverage (CSC) and to identify barriers to the uptake of cataract services among adults aged >or=30 years in Pakistan. METHODS: Probability proportional-to-size procedures were used to select a nationally representative sample of adults. Each subject underwent interview, visual acuity measurement, autorefraction, biometry and ophthalmic examination. Those that saw <6/12 in either eye underwent a more intensive examination procedure including corrected visual acuity, slit lamp and dilated fundus examination. CSC was calculated for different levels of visual loss by person and by eye. Individuals with <6/60 in the better eye as a result of cataract were interviewed regarding barriers. RESULTS: 16 507 Adults were examined (95.5% response rate). The crude prevalence of blindness (presenting <3/60 in the better eye) caused by bilateral cataract was 1.75% (95% CI 1.55%, 1.96%). 1317 Participants (633 men; 684 women) had undergone cataract surgery in one or both eyes, giving a crude prevalence of 8.0% (95% CI 7.6%, 8.4%). The CSC (persons) at <3/60, <6/60 and <6/18 were 77.1%, 69.3% and 43.7%, respectively. The CSC (eyes) at <3/60, <6/60 and <6/18 were 61.4%, 52.2% and 40.7%, respectively. Cost of surgery (76.1%) was the main barrier to surgery. CONCLUSION: Approximately 570 000 adults are estimated to be blind (<3/60) as a result of cataract in Pakistan, and 3,560000 eyes have a visual acuity of <6/60 because of cataract. Overall, the national surgical coverage is good but underserved populations have been identified

Magnetic dipole moments in single and coupled split-ring resonators

We examine the role of magnetic dipoles in single and coupled pairs of metallic split-ring resonators by numerically computing their magnitude and examining their relative contributions to the scattering cross section. We demonstrate that magnetic dipoles can strongly influence the scattering cross section along particular directions. It is also found that the magnetic dipole parallel to the incident magnetic field and/or high-order multipoles may play a significant role in the linear response of coupled split-ring resonators.Comment: 7 pages, 3 figures, 1 tabl

A test of the Poincare dodecahedral space topology hypothesis with the WMAP CMB data

It has been suggested by Roukema and coworkers (hereafter R04) that the topology of the Universe as probed by the ``matched circles'' method using the first year release of the WMAP CMB data, might be that of the Poincar\'e dodecahedral space (PDS) model. An excess in the correlation of the ``identified circles'' was reported by R04, for circles of angular radius of ~11 deg for a relative phase twist -36deg, hinting that this could be due to a Clifford translation, if the hypothesized model were true. R04 did not however specify the statistical significance of the correlation signal. We investigate the statistical significance of the signal using Monte Carlo CMB simulations in a simply connected Universe, and present an updated analysis using the three-year WMAP data. We find that our analyses of the first and three year WMAP data provide results that are consistent with the simply connected space at a confidence level as low as 68%.Comment: 8 pages, 6 figures, typo corrected/replaced to match version published in A&

Transactions of the Royal Society of Tropical Medicine and Hygiene (2006) 100, 149—157 Rapid assessment for prioritisation of trachoma control at community level in one district of the

Summary The objective of this study was to use a modified Lot Quality Assurance Sampling methodology to classify communities according to prevalence of active trachoma and to estimate the prevalence of trachoma and trichiasis in Nioro department, Kaolack Region, Senegal. A survey was conducted using twostage cluster sampling to select 50 children aged 2—5 years in each of 33 clusters. In total 1648 children were examined for active trachoma. Information on trachoma risk factors was collected through interviews with the mother or the household head of the child. Adults (&gt;40 years) with trichiasis were identified through case finding. Nineteen clusters had a low prevalence of active trachoma in children aged 2—5 years (&lt;20%), 11 had medium prevalence (20—40%) and three had high prevalence (&gt;40%). The prevalence of active trachoma in children aged 2—5 years was 17.4 % (95 % CI 12.9—21.8%). Multivariate-adjusted predictors of active trachoma were: age, facial cleanliness, hygiene practices and keeping cattle in the household. The prevalence of trichiasis in adults aged over 40 years was 1.77 % (95 % CI 1.24—2.51), equating to 985 adults (95 % CI 765—1250) with trichiasis in Nioro department. In conclusion, a survey using rapid methodology showed that trachoma is a problem of public significance in Nioro department

Rapid assessment of visual impairment (RAVI) in marine fishing communities in South India - study protocol and main findings

<p>Abstract</p> <p>Background</p> <p>Reliable data are a pre-requisite for planning eye care services. Though conventional cross sectional studies provide reliable information, they are resource intensive. A novel rapid assessment method was used to investigate the prevalence and causes of visual impairment and presbyopia in subjects aged 40 years and older. This paper describes the detailed methodology and study procedures of Rapid Assessment of Visual Impairment (RAVI) project.</p> <p>Methods</p> <p>A population-based cross-sectional study was conducted using cluster random sampling in the coastal region of Prakasam district of Andhra Pradesh in India, predominantly inhabited by fishing communities. Unaided, aided and pinhole visual acuity (VA) was assessed using a Snellen chart at a distance of 6 meters. The VA was re-assessed using a pinhole, if VA was < 6/12 in either eye. Near vision was assessed using N notation chart binocularly. Visual impairment was defined as presenting VA < 6/18 in the better eye. Presbyopia is defined as binocular near vision worse than N8 in subjects with binocular distance VA of 6/18 or better.</p> <p>Results</p> <p>The data collection was completed in <12 weeks using two teams each consisting of one paramedical ophthalmic personnel and two community eye health workers. The prevalence of visual impairment was 30% (95% CI, 27.6-32.2). This included 111 (7.1%; 95% CI, 5.8-8.4) individuals with blindness. Cataract was the leading cause of visual impairment followed by uncorrected refractive errors. The prevalence of blindness according to WHO definition (presenting VA < 3/60 in the better eye) was 2.7% (95% CI, 1.9-3.5).</p> <p>Conclusion</p> <p>There is a high prevalence of visual impairment in marine fishing communities in Prakasam district in India. The data from this rapid assessment survey can now be used as a baseline to start eye care services in this region. The rapid assessment methodology (RAVI) reported in this paper is robust, quick and has the potential to be replicated in other areas.</p

Milk production per cow and per hectare of spring-calving dairy cows grazing swards differing in Lolium perenne L. ploidy and Trifolium repens L. composition

peer-reviewedGrazed grass is the cheapest feed available for dairy cows in temperate regions; thus, to maximize profits, dairy farmers must optimize the use of this high-quality feed. Previous research has defined the benefits of including white clover (Trifolium repens L.) in grass swards for milk production, usually at reduced nitrogen usage and stocking rate. The aim of this study was to quantify the responses in milk production of dairy cows grazing tetraploid or diploid perennial ryegrass (Lolium perenne L.; PRG) sown with and without white clover but without reducing stocking rate or nitrogen usage. We compared 4 grazing treatments in this study: tetraploid PRG-only swards, diploid PRG-only swards, tetraploid with white clover swards, and diploid with white clover swards. Thirty cows were assigned to each treatment, and swards were rotationally grazed at a farm-level stocking rate of 2.75 cows/ha and a nitrogen fertilizer rate of 250 kg/ha annually. Sward white clover content was 23.6 and 22.6% for tetraploid with white clover swards and diploid with white clover swards, respectively. Milk production did not differ between the 2 ploidies during this 4-yr study, but cows grazing the PRG-white clover treatments had significantly greater milk yields (+596 kg/cow per year) and milk solid yields (+48 kg/cow per year) compared with cows grazing the PRG-only treatments. The PRG-white clover swards also produced 1,205 kg of DM/ha per year more herbage, which was available for conserving and buffer feeding in spring when these swards were less productive than PRG-only swards. Although white clover is generally combined with reduced nitrogen fertilizer use, this study provides evidence that including white clover in either tetraploid or diploid PRG swards, combined with high levels of nitrogen fertilizer, can effectively increase milk production per cow and per hectar

Microbial composition and omasal flows of bacterial, protozoal, and nonmicrobial amino acids in lactating dairy cows fed fresh perennial ryegrass (Lolium perenne L.) not supplemented or supplemented with rolled barley

peer-reviewedThe objective of this study was to evaluate the effect of rolled barley supplementation on microbial composition and omasal flows of bacterial, protozoal, and nonmicrobial AA in cows fed fresh perennial ryegrass (Lolium perenne L.; PRG). Ten ruminally cannulated multiparous Holstein cows averaging (mean ± standard deviation) 49 ± 23 d in milk and 513 ± 36 kg of body weight were assigned to 1 of 2 treatments in a switchback design. The treatment diets were PRG only or PRG plus 3.5 kg of dry matter rolled barley (G+RB). The study consisted of three 29-d periods where each period consisted of 21 d of diet adaptation and 8 d of data and sample collection. A double-marker system was used to quantify nutrient flow entering the omasal canal along with 15N-ammonium sulfate to label and measure the microbial and nonmicrobial omasal flow of AA. Overall, rolled barley supplementation had no effect on the AA composition of the omasal liquid-associated and particle-associated bacteria. Rolled barley supplementation affected the AA concentrations of omasal protozoa; however, the differences were nutritionally minor. Particle-associated bacteria AA flow was increased for all AA, except for Trp and Pro, in cows fed the G+RB diet. Rolled barley supplementation had no effect on protozoal AA flow. On average, protozoa accounted for 23% of the microbial essential AA flow, which ranged from 17 to 28% for Trp and Lys, respectively. The flow of all AA in omasal true digesta increased in cows fed the G+RB diet compared with the PRG-only diet, resulting in a 228 g/d increase in total AA flow in cows fed the G+RB diet. This increase in total AA flow in cows fed the G+RB diet was due to an increase in microbial AA flow. Rolled barley supplementation had no effect on nonmicrobial AA flow. The nonmicrobial AA flow modestly contributed to total AA flow, accounting for 15.6% on average. These results indicated that extensive ruminal degradation of PRG AA occurred (83.5%), and we demonstrated that cows consuming PRG-based diets exhibit a large dependence on microbial AA to support metabolizable AA supply. Rolled barley supplementation can increase the omasal flow of microbial AA in cows consuming PRG-based diets. However, further research is required to elucidate if this increased AA supply can support higher milk yield under such dietary conditions

An assessment of the production, reproduction, and functional traits of Holstein-Friesian, Jersey × Holstein-Friesian, and Norwegian Red × (Jersey × Holstein-Friesian) cows in pasture-based systems

Peer-ReviewedPasture-based production systems typically require highly fertile, healthy, and robust genetics, with greater emphasis on milk solids (MSo; kg of fat + protein) production as opposed to milk yield. This study assessed milk production, production efficiency, reproductive performance, body weight (BW), body condition score, and functional traits in 3 different dairy cow genotypes: Holstein-Friesian (HF), Jersey × Holstein-Friesian (JEX), and Norwegian Red × (Jersey × Holstein- Friesian) (3-way). The 3 genotypes were rotationally grazed on 4 different grazing treatments after calving in spring and were stocked at a rate of 2.75 cows/ha. Holstein-Friesian cows produced higher daily and total milk yields compared with JEX and 3-way cows (5,718 vs. 5,476 and 5,365 kg/cow, respectively). However, JEX and 3-way cows had higher milk fat and protein contents (4.86 and 4.75%, respectively, for JEX and 3.87 and 3.88%, respectively, for 3-way) compared with HF (4.52 and 3.72%), resulting in similar MSo yield for JEX and HF (469 and 460 kg/cow) and slightly lower MSo yield for 3-way (453 kg/cow) compared with JEX. As parity increased, milk and MSo yield per cow increased. Reproductive performance was not significantly different between the 3 genotypes, which had similar 24-d submission rates, 6-wk pregnancy rates, and overall pregnancy rates over the 4-yr period. No difference in calving difficulty, incidence of mastitis, or incidence of lameness was observed among the 3 genotypes. Body weight was significantly different among all 3 genotypes, with HF being the heaviest followed by 3-way and JEX (530, 499, and 478 kg, respectively), and 3-way cows had a higher body condition score throughout lactation compared with HF and JEX cows. The differences in BW coupled with similar MSo production resulted in JEX cows having the highest production efficiency (4.58 kg of MSo/kg of metabolic BW), 3-way cows being intermediate (4.30 kg of MSo/kg of metabolic BW), and HF cows having the lowest (4.16 kg of MSo/kg of metabolic BW). In conclusion, HF herds with poor reproductive performance and low milk fat and protein contents are likely to benefit considerably from crossbreeding with Jersey, and all herds are likely to benefit in terms of production efficiency. However, where herd performance, particularly in relation to reproductive performance, is comparable with HF in the current study, crossbreeding with Jersey or Norwegian Red is unlikely to lead to significant improvements in overall herd performance

The effect of Lolium perenne L. ploidy and Trifolium repens L. inclusion on dry matter intake and production efficiencies of spring-calving grazing dairy cows

peer-reviewedThe objective of this study was to investigate the effect of perennial ryegrass (Lolium perenne L.; PRG) ploidy and white clover (Trifolium repens L.) inclusion on milk production, dry matter intake (DMI), and milk production efficiencies. Four separate grazing treatments were evaluated: tetraploid PRG only, diploid PRG only, tetraploid PRG with white clover, and diploid PRG with white clover. Individual DMI was estimated 8 times during the study (3 times in 2015, 2 times in 2016, and 3 times in 2017) using the n-alkane technique. Cows were, on average, 64, 110, and 189 d in milk during the DMI measurement period, corresponding to spring, summer, and autumn, respectively. Measures of milk production efficiency were total DMI/100 kg of body weight (BW), milk solids (kg of fat + protein; MSo)/100 kg of BW, solids-corrected milk/100 kg of BW, and MSo/kg of total DMI. Perennial ryegrass ploidy had no effect on DMI; however, a significant increase in DMI (+0.5 kg/cow per day) was observed from cows grazing PRG-white clover swards compared with PRG-only swards. Sward white clover content influenced DMI as there was no increase in DMI in spring (9% sward white cover content), whereas DMI was greater in summer and autumn for cows grazing PRG-white clover swards (+0.8 kg/cow per day) compared with PRG-only swards (14 and 23% sward white clover content, respectively). The greater DMI of cows grazing PRG-white clover swards led to increased milk (+1.3 kg/cow per day) and MSo (+0.10 kg/cow per day) yields. Cows grazing PRG-white clover swards were also more efficient for total DMI/100 kg of BW, solids-corrected milk/100 kg of BW, and MSo/100 kg of BW compared with cows grazing PRG-only swards due to their similar BW but higher milk and MSo yields. The results highlight the potential of PRG-white clover swards to increase DMI at grazing and to improve milk production efficiency in pasture-based systems