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Allen Foster

Publications and source records attributed to Allen Foster.

At least 19 recordsLinked to original sources
PubMed2006

Outcomes of cataract surgery in Pakistan: results from The Pakistan National Blindness and Visual Impairment Survey.

AIM: To evaluate the outcomes of cataract surgery in Pakistan. METHODS: Cross-sectional, nationally representative sample of 16 507 adults (aged >or=30 years). Each underwent interview, logarithm of the minimum angle of resolution visual acuity (VA), autorefraction, examination of optic disc. Those with <6/12 VA on presentation underwent best-corrected VA and dilated biomicroscopic ocular examination. RESULTS: 1317 subjects (633 men) had undergone surgery in one or both eyes. Of the 1788 operated eyes, 1099 (61%) had undergone intracapsular cataract extraction (ICCE) and 607 (34%) extracapsular surgery with an intraocular lens (ECCE+IOL). Presenting VA: 275 (15.4%) eyes: 6/12 or better; 253 (14.1) <6/12 >or=6/18; 632 (35.3%) 6/18 to 6/60; 85 (4.8%): 6/60 to 3/60; 528 (29.5%): <3/60. With "best" refractive correction, these values were: 563 (31.5%), 332 (18.6%), 492 (27.5%), 61 (3.4%), 334 (18.7%), respectively. Of the 1498 eyes with VA or=4 years before the survey. CONCLUSION: Almost a third of cataract operations result in a presenting VA of <6/60, which could be halved by appropriate refractive correction. This study highlights the need for an improvement in quality of surgery with a more balanced distribution of services.

Adult↗
PubMed2006

Rapid assessment of avoidable blindness in Nakuru district, Kenya.

OBJECTIVES: To estimate the prevalence of avoidable blindness in > or =50-year-olds in Nakuru district, Kenya, and to evaluate the Rapid Assessment for Avoidable Blindness (RAAB), a new methodology to measure the magnitude and causes of blindness. DESIGN: Cross-sectional population-based survey. PARTICIPANTS: Seventy-six clusters of 50 people 50 years or older were selected by probability proportionate to size sampling of clusters. Households within clusters were selected through compact segment sampling. Three thousand seven hundred eighty-four eligible subjects were selected, of whom 3503 (92.6%) were examined. METHODS: Participants underwent a comprehensive ophthalmic examination in their homes by an ophthalmologist, including measurement of visual acuity (VA) with a tumbling-E chart and the diagnosis of the principal cause of visual impairment. Those who had undergone cataract surgery were questioned about the details of the operation and their satisfaction with surgery. Those who were visually impaired from cataract were asked why they had not gone for surgery. MAIN OUTCOME MEASURES: Visual acuity and principal cause of VA<6/18. RESULTS: The prevalence of bilateral blindness (presenting VA < 3/60) was 2.0% (95% confidence interval [CI], 1.5%-2.4%), and prevalence of bilateral visual impairment (VA of <6/18-> or =6/60) was 5.8% (95% CI, 4.8%-6.8%) in the sample. Definite avoidable causes of blindness (i.e., cataract, refractive error, trachoma, and corneal scarring) were responsible for 69.6% of bilateral blindness and 74.9% of bilateral visual impairment. Cataract was the major cause of blindness (42.0%) and visual impairment (36.0%). The cataract surgical coverage was high, with 78% of those with bilateral cataract who needed surgery having had surgery at VA<3/60. The quality of surgery was of concern because 22% of the 222 eyes that had undergone cataract surgery had VA<6/60 with best correction. The main barriers to surgery were lack of awareness and cost. The RAAB methodology was easy to use, and each team could visit one cluster per day. CONCLUSIONS: The prevalence of blindness in > or =50-year-olds in Nakuru district was low, in part due to the high cataract surgical coverage. The RAAB is easy to use and inexpensive and provides information about the magnitude and causes of avoidable blindness that can be used for planning and monitoring eye care services.

Blindness↗
PubMed2006

The relationship between prevalence of active trachoma, water availability and its use in a Tanzanian village.

This study aimed to establish the relationship between the prevalence of active trachoma in children, water availability and household water use in a village in Tanzania. Nine hundred and fourteen children aged 1-9 years were examined for signs of trachoma. Data were collected on time taken to collect water, amount of water collected and other trachoma risk factors. In a sub-study, 99 randomly selected households were visited twice daily on two consecutive days to document patterns of water use. The prevalence of active trachoma in the children examined was 18.4% (95% CI 15.9-20.9). Active trachoma prevalence increased with increasing water collection time (OR 2.25; 95% CI 1.13-4.46) but was unrelated to the amount of water collected. In the sub-study, active trachoma prevalence was substantially lower in children from households where more water was used for personal hygiene (P for trend < or =0.01), independent of the total amount of water used. The allocation of water to hygiene was predicted by lower water collection time. The key element in the relationship between water availability and trachoma is the allocation of water within households. Collection time may influence both the quantity of water collected and its allocation within the household.

Child↗
PubMed2006

Mapping the global distribution of trachoma.

OBJECTIVE: We aimed to summarize and map the existing global population-based data on active trachoma and trichiasis. Detailed distribution maps of various infectious diseases have proved a valuable tool in their control. Such maps play an important role in assessing the magnitude of the problem, defining priority areas for control, monitoring changes, and advocacy. Until now, information on trachoma prevalence at within country levels has not been systematically collated, analysed and reported. METHODS: We gathered the last 18 years' worth of reported data on active trachoma in children aged less than 10 years, and the last 25 years of reported trichiasis in adults aged 15 years and over from 139 population-based surveys in 33 countries. We collated these data into one database using the "district" (second administrative level) as the standard unit of reporting. We used Geographical Information Systems as a database and cartographic tool to generate a global map of the prevalence of trachoma and trichiasis. FINDINGS: We obtained data on active trachoma and trichiasis from 18 countries in the WHO African Region, 6 in the Eastern Mediterranean Region, 3 in the South-East Asia Region, 3 in the Western Pacific Region and 2 in the Region of the Americas. In 23 countries suspected of having endemic trachoma no reliable district-level population-based data were available. In China and India, data were limited to a few districts. The data highlighted important regional differences and marked national variations in prevalence of active trachoma and trichiasis. CONCLUSION: This is the first attempt to summarize and map the existing population-based data on active trachoma and trichiasis. The lack of data in many countries remains an important obstacle to trachoma control efforts.

Adolescent↗
PubMed2006

A proposed rapid methodology to assess the prevalence and causes of blindness and visual impairment.

PURPOSE: To determine whether a sample of the 50-year-old and above population would provide comparable information to a total population-based survey. METHODS: In 1996, a national eye survey of the total population in The Gambia was undertaken and the results concerning the prevalence and distribution of blindness and low vision have been reported. The same data set was used to analyse the prevalence and causes of blindness and low vision in people aged 50 years and above, and to compare the findings with the total population. RESULTS: Of 55 bilaterally blind people in the total population, 83.6% were 50 years of age or older. The distribution by cause of blindness was similar for the total population and for those aged 50 years and above. Cataract and uncorrected aphakia accounted for 46% and 13%, respectively, in the total population and 48% and 15% in the 50 year and above age group. Trachoma accounted for 5% and 4%, and other corneal opacities for 16% and 13%, respectively. Phthisis bulbi, which may follow perforated corneal ulcers, ocular trauma/surgery or occasionally severe uveitis, accounted for 4% in both age groups, and glaucoma accounted for 9% in the total population and 11% in the 50 year plus group. CONCLUSION: Assessment of the 50 year and above age group proved to be a good indicator for the causes of blindness and visual impairment in the total population and for determining those causes of blindness that are avoidable. Such an assessment requires a much smaller sample size, less than 20% of the sample size for the total population, and is likely to be less expensive.

Adolescent↗
PubMed2006

The long-term natural history of trachomatous trichiasis in the Gambia.

PURPOSE: Trachoma is the leading infectious cause of blindness. However, there are few data on the natural history of trachomatous trichiasis to guide program planning or that investigate its pathogenesis. METHODS: A cohort of Gambians with trichiasis in one or both eyes who had declined surgery was observed. Clinical examinations were performed at baseline and 4 years later. Conjunctival swab samples were collected for Chlamydia trachomatis PCR and bacteriology. RESULTS: One hundred fifty-four people were examined at baseline and 4 years later (241 nonsurgical eyes). At baseline 124 (52%) eyes had major trichiasis (5+ lashes), 75 (31%) minor trichiasis (1-4 lashes), and 42 (17%) no trichiasis. By 4 years, trichiasis had developed in 12 (29%) of 42 previously unaffected eyes. Minor trichiasis progressed to major in 28 (37%) of 75 eyes. New corneal opacification more commonly developed in eyes that had major (10%) compared to minor (5%) trichiasis at baseline. Bacterial infection was common (23%), becoming more frequent with increasing trichiasis. C. trachomatis infection was rare (1%). Conjunctival inflammation was common (29%) and was associated with progressive trichiasis and corneal opacification. CONCLUSIONS: Trichiasis progressed in the long-term in this environment, despite a low prevalence of C. trachomatis. Blinding corneal opacification develops infrequently, unless major trichiasis is present. Epilation and early surgery need to be formally compared for the management of minor trichiasis. The pathologic correlates and promoters of conjunctival inflammation need to be investigated.

Aged↗
PubMed2006

Operational evaluation of the use of photographs for grading active trachoma.

We evaluated the reliability of photographs to verify field diagnoses of active trachoma. We examined 956 residents of a trachoma-endemic village for signs of trachoma using the World Health Organization simplified grading system. Two photographs of the right eye of 948 persons were independently graded (masked to field assessment) by the field examiner and two other experienced graders. There was only moderate agreement between field assessment and the subsequent photographic evaluations by the three graders. When we counted ungradable photographs as disagreements, mean kappa scores for the signs trachomatous inflammation (follicular [TF]) and trachomatous inflammation (intense [TI]) were 0.44 and 0.51, respectively. There was also only fair-to-moderate agreement between the three assessments (by different examiners) of the photographs. Either the signs TF and TI themselves are not as reliable as previously believed, or photographs should be used for their diagnosis only when reliability testing demonstrates better agreement than found here.

Adolescent↗
PubMed2005

Infection with Chlamydia trachomatis after mass treatment of a trachoma hyperendemic community in Tanzania: a longitudinal study.

BACKGROUND: Data from studies done in communities where trachoma is mesoendemic suggest that ocular infection with Chlamydia trachomatis can be eliminated after one mass treatment with antibiotics. However, there are no comparable long-term data from trachoma hyperendemic communities. Our aim, therefore, was two-fold: first, to ascertain the disease pattern of trachoma and ocular infection with C trachomatis in a trachoma hyperendemic community after mass treatment; and, second, to ascertain the risk factors for incident infection. METHODS: We did a longitudinal study of a trachoma hyperendemic community (n=1017) in Tanzania. We did surveys, including ocular swabs, at baseline, 2, 6, 12, and 18 months to identify the presence, and quantity, of C trachomatis after single mass treatment of all individuals aged 6 months or older with azithromycin 20 mg per kg; pregnant women without clinical disease received topical tetracycline. FINDINGS: Mass treatment (coverage 86%) significantly reduced the prevalence of infection from 57% (495 of 871) to 12% (85 of 705) at 2 months. Infection remained fairly constant to 12 months, with evidence of increasing numbers and load of infection by 18 months post-treatment. Incident infection at 6 months was 3.5-times more likely if another member of the household had more than 19 organisms per swab at 2 months. Travel outside the village, and visitors to the household, did not increase the risk of infection within households up to 12 months. INTERPRETATION: In this trachoma hyperendemic community, infection levels after high antibiotic coverage persisted at a low level to 18 months, with evidence for re-emergence after 1 year. Fairly light loads of infection were associated with household transmission. Yearly mass treatment over a few years could be sufficient to eliminate infection.

Administration, Oral↗
PubMed2005

Analysis of costs and benefits of the Gambian Eye Care Program.

OBJECTIVE: To estimate the net benefit of the Gambian Eye Care Program (GECP) using a limited definition of benefits from a societal perspective. METHODS: The number of cases of blindness avoided was modeled using population projections, population-based blindness survey estimates from 1986 and 1996, and reported blindness-related mortality differences. Benefits were measured as lifetime productivity gains that resulted from the cases of blindness avoided between the surveys. Costs included all contributions to GECP between the surveys. RESULTS: In 1996, 1658 fewer individuals were blind than would have been without GECP. The present value of costs was 1.28 US million dollars (1995 dollars). Although the net benefit between the blindness surveys was negative, the net lifetime benefit was 1.01 US million dollars (1995 dollars), yielding an internal rate of return of 10%. In the primary sensitivity analysis, assuming similar benefits to Senegalese citizens, who accounted for 30% of patients, the internal rate of return was 19%. Upper bound sensitivity analyses result in internal rates of return higher than 20%. CONCLUSION: In one sub-Saharan African country with avoidable blindness due to cataract and eye infections, the internal rate of return of a national eye care program was substantial when using a limited definition of benefit.

Adolescent↗
PubMed2005

Acceptability of azithromycin for the control of trachoma in Northern Tanzania.

Trachoma causes blindness; the prevention strategy includes mass antibiotic treatment. In a community in Northern Tanzania offered mass treatment with azithromycin for the control of trachoma, we used focus group discussions, individual interviews, questionnaires and direct observation to quantify, explore and contextualize reasons for acceptance or refusal of the drug. In the village studied, 76% of the population eligible to receive azithromycin were treated. Uptake was significantly higher among women (79% treated) than men (72%). Factors affecting acceptability included: local prevention norms (such as the belief that injections, rather than oral medicine, should be used for prevention); perceptions of drugs in general and azithromycin in particular; perceptions of the distribution team's expertise; witnessing adverse effects in others; and the timing, quality and quantity of information about azithromycin and its availability. Familiarity with trachoma as a blinding disease was significantly associated with uptake. Individuals who refused treatment seemed to be less altruistic than other respondents. Neither socio-economic status nor use of traditional healers was related to uptake. Pre-distribution community assessment and community education, advance notice of the distribution, standardized distribution guidelines and improved distributor training are recommended to maximize acceptance of azithromycin in future campaigns.

Adult↗
PubMed2005

The Pakistan national blindness and visual impairment survey--research design, eye examination methodology and results of the pilot study.

PURPOSE: To establish age- and sex-specific prevalence rates and causes of blindness and low vision in children aged 10 to 15 years and adults aged 30 years and older in Pakistan. METHODS: Multi-stage, stratified (rural/urban), cluster random sampling, with probability proportional-to-size procedures, was utilised to select a cross-sectional, nationally representative sample of adults (16,600 subjects) and children (6,000 subjects). Each subject underwent: interview, visual acuity (logMAR), autorefraction and optic disc examination. Those that saw < 6/12 in either eye underwent corrected visual acuity and dilated posterior segment examination. RESULTS: The results of a pilot survey are reported in this paper. In the two rural pilot sites, 159 subjects (including 47 children) were examined; 50% were male. Thirty seven adults (23.3%) but no children saw worse than 6/12 in either eye. Two subjects were blind (corrected visual acuity) in the better eye, and 11 were visually impaired. Refractive error was the main cause (in 22 eyes (39% of the total of 56 eyes)) of < 6/12 visual acuity, followed by cataract (12 eyes), uncorrected aphakia (6 eyes) and age-related macular disease (3 eyes). CONCLUSIONS: The pilot survey demonstrated that the proposed examination process for the main survey is feasible. Particular strengths of this survey include the use of logMAR visual acuity testing and autorefraction of all subjects, a dilated posterior segment examination, and the use of a 'less than 6/12' threshold for further examination. This lower threshold addresses the burden of refractive error, which, with cataract, are two of the diseases specifically targeted by Vision 2020.

Adolescent↗
PubMed2005

Participatory evaluations of trachoma control programmes in eight countries.

OBJECTIVES: Trachoma is a major cause of blindness. The objective of this initiative was to conduct participatory process evaluations of the trachoma control programmes receiving support from the International Trachoma Initiative in eight countries. METHODS: During each 2- to 4-week evaluation we analysed information collected at the central, district and community level through interviews, focus groups, questionnaires, direct observation of trachoma control activities, and existing data. RESULTS: Mapping and assessment of disease prevalence had been completed in four of eight countries. Integration of trachoma control activities into national planning and district-level service provision varied. Intersectoral partnerships to implement the SAFE strategy (i.e. surgery, antibiotics, facial cleanliness and environmental change) were well established in a few countries. In all eight countries, the number of surgeries performed annually was insufficient; and quality of surgery was rarely monitored. Mass distribution of antibiotics was carried out well in extremely resource-poor settings and good coverage was achieved, although the strategy for antibiotic distribution varied. Inadequate water and sanitation remained a major problem in all programme areas. Monitoring of programme activities was generally inadequate. The Morocco programme is an example from which lessons and processes can be learnt and adapted to other programme countries. CONCLUSIONS: Significant achievements have been made in implementing the SAFE strategy. Scaling up of activities to true national coverage should be planned and implemented provided the resources can be made available. Further standardization of how to assess, implement and monitor trachoma control activities will facilitate expansion of the programme.

Africa↗
PubMed2005

Impact of mass distribution of azithromycin on the antibiotic susceptibilities of ocular Chlamydia trachomatis.

In a community of Tanzania where trachoma is endemic, we cultured conjunctival swabs from all residents who had active trachoma and were PCR positive for ocular Chlamydia trachomatis, both before (43 isolates) and 2 months after (9 isolates) mass antibiotic treatment. No clinically or programmatically significant increase in azithromycin or tetracycline resistance was observed.

Azithromycin↗
PubMed2005

Mass treatment and the effect on the load of Chlamydia trachomatis infection in a trachoma-hyperendemic community.

PURPOSE: Trachoma remains a leading cause of blindness. Determining the most effective antibiotic treatment strategy is essential for the success of country-based trachoma control programs. METHODS: Baseline and 2-month follow-up examinations were performed in a trachoma-hyperendemic village. All residents were offered azithromycin for trachoma after baseline was determined. Infection with Chlamydia trachomatis and chlamydial load were determined by PCR. Clinical trachoma status was evaluated. A high chlamydial load was defined as a higher than median chlamydial load among those with infection. Risk factors were examined in multiple logistic regression models. Associations are presented as odds ratios and 95% confidence intervals. RESULTS: At baseline, 57% of participants were infected with C. trachomatis. Although clinical trachoma correlated with infection, 23% of participants with high chlamydial loads showed no clinical signs. Adults represented only 10% of the population with high loads. Treatment significantly decreased the proportion positive in the community and the load in the community. However, 27% of individuals with high loads at baseline who received treatment also were infected at 2 months. Of those, 93% with high loads at 2 months were aged < or =10 years. CONCLUSIONS: Although most of the chlamydial load in this community resided in children, 10% of the high load resided in adults, most of whom did not have follicular trachoma and in whom the infection would be missed under treatment strategies that focus on clinical disease or children. These data support a mass treatment strategy for hyperendemic communities, at least as a first approach. In addition, treatment of children age < or =2 years should be reexamined, as >30% with high loads at baseline remained infected at 2 months, despite monitored treatment according to weight.

Adolescent↗
PubMed2005

Risk factors for postsurgical trichiasis recurrence in a trachoma-endemic area.

PURPOSE: The World Health Organization recommends trichiasis surgery to prevent blindness caused by trachoma; however, recurrence is common. Risk factors for recurrence have not been widely studied, particularly in trachoma hyperendemic areas. METHODS: Three hundred ninety-four persons with trichiasis in Tanzania were examined. Participants had undergone surgery >18 months before the study. Trichiasis recurrence and active trachoma at study visit were assessed. Ocular swabs were collected and tested for Chlamydia trachomatis. Household members were examined for active trachoma. RESULTS: Of the surgical eyes, 28% had recurrence; 40% of patients had recurrence in one or both eyes. Rates did not vary by time since surgery. Eye-level recurrence rates varied significantly across districts, ranging from 16% to 38%. Current chlamydial infection among surgical cases was low (6%) and was not associated with recurrence. Recurrence was associated with tarsal conjunctival inflammation (OR: 2.4; 95% confidence interval [CI]: 1.6-3.8) and residence in the Kongwa district (OR: 2.3; 95% CI: 1.2-4.6). CONCLUSIONS: Recurrence after trichiasis surgery is high, suggesting that vigilant follow-up in surgical cases is needed to reduce blindness. Recurrence is associated with evidence of inflammation in the tarsal conjunctiva, although it is not clear whether the inflammation contributes to recurrence, or is a result of the recurrence. Longitudinal studies of trichiasis patients after surgery are needed.

Aged↗
PubMed2004

Mass treatment with single-dose azithromycin for trachoma.

BACKGROUND: Trachoma, caused by repeated ocular infection with Chlamydia trachomatis, is an important cause of blindness. Current recommended dosing intervals for mass azithromycin treatment for trachoma are based on a mathematical model. METHODS: We collected conjunctival swabs for quantitative polymerase-chain-reaction assay of C. trachomatis before and 2, 6, 12, 18, and 24 months after mass treatment with azithromycin in a Tanzanian community in which trachoma was endemic. For ethical reasons, at 6, 12, and 18 months, we gave tetracycline eye ointment to residents who had clinically active trachoma. RESULTS: At baseline, 956 of 978 residents (97.8 percent) received either one oral dose of azithromycin or (if azithromycin was contraindicated) a course of tetracycline eye ointment. The prevalence of infection fell from 9.5 percent before mass treatment to 2.1 percent at 2 months and 0.1 percent at 24 months. The quantitative burden of ocular C. trachomatis infection in the community was 13.9 percent of the pretreatment level at 2 months and 0.8 percent at 24 months. At each time point after baseline, over 90 percent of the total community burden of C. trachomatis infection was found among subjects who had been positive the previous time they were tested. CONCLUSIONS: The prevalence and intensity of infection fell dramatically and remained low for two years after treatment. One round of very-high-coverage mass treatment with azithromycin, perhaps aided by subsequent periodic use of tetracycline eye ointment for persons with active disease, can interrupt the transmission of ocular C. trachomatis infection.

Adolescent↗