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ABSTRACT Aim To investigate the prevalence and causes of optic neuropathy, reported as epidemic in 1997, among secondary school students in Dar esc Salaam, Tanzania. Patients and methods First year students (n=10 892) from 63 secondary schools located within 30 km from the base hospital were interviewed and had a visual acuity (VA) screening test. Students failing the 6/12-line in either eye were defined as having "poor eyesight" and referred to the base hospital where an optometrist retested VA and refracted them. An ophthalmologist examined students with VA of 6/12 or worse in either eye and visual impairment was defined as VA of worse than 6/12 with best correction. Associations between optic neuropathy, socioeconomic status and educational results were investigated. Results Students' ages ranged from 12 to 22 (mean 15.2) years; 50.6% were male. The prevalence of optic neuropathy was 0.3 (SD 0.051)%. The condition affected older students and was associated with the family having fewer economic possessions (car, computer, television). Optic neuropathy accounted for 19/33 (58%) of bilateral visual impairment cases. No effect of the disease on educational performance was identified. Conclusion Optic neuropathy remains a significant problem in this population and can now be termed endemic rather than epidemic. Further research into its causes is required. [ABSTRACT FROM AUTHOR]

Purpose: To compare whether free spectacles or only a prescription for spectacles influences wearing rates among Tanzanian students with un/undercorrected refractive error (RE). Methods: Design. Cluster randomised trial. Setting: 37 secondary schools in Dar es Salaam, Tanzania. Participants: Distance visual acuity was measured in 6,904 year-1 students (90.2% response rate; median age 14 years; range 11-25 years) using a Snellen E-chart. 135 had RE requiring correction. Interventions: Schools were randomly allocated to free spectacles (arm A) or prescription only (arm B). Primary outcome: Spectacle use at 3 months. Results: The prevalence of un/undercorrected RE was 1.8% (95% CI: 1.5 to 2.2%). At 3 months, 27/58 (47%) students in arm A were wearing spectacles or had them at school compared with 13/50 (26%) in arm B (adjusted OR 2.4, 95% CI 1.0 to 6.7). Free spectacles and myopia were independently associated with spectacle use. Conclusions: The low prevalence of un/undercorrected RE and poor uptake of spectacles, even when provided free, raises doubts about the value of vision-screening programmes in Tanzanian secondary schools. Policy decisions on school vision screening in middle- and low-income countries should take account of the cost- effectiveness as well as competing demands for scarce resources. [ABSTRACT FROM AUTHOR]

OBJECTIVE:: This study validates different definitions of reported night blindness (XN) in a vitamin A deficient African population with no local term for XN. DESIGN:: Case-control study with follow-up after treatment. SETTING:: Eight primary schools and health centres in rural Tanzania. SUBJECTS:: A total of 1214 participants were screened for reported XN and other eye signs of xerophthalmia: 461 children aged 24-71 months, 562 primary school-age children and 191 pregnant or breast-feeding women. All 152 cases of reported XN were selected for the validation study and group matched with 321 controls who did not complain of XN. XN reports were validated against serum retinol concentrations and pupillary dark adaptation measurements in cases and controls. INTERVENTION:: All children and women who reported XN or had other signs of active xerophthalmia were treated with vitamin A and followed up 3-4 weeks later. Half of the untreated control group who had their serum retinol examined in the baseline examination were also followed up. RESULTS:: The overall prevalence of reported XN was 12.5%. At baseline, mean pupillary threshold (-1.52 vs -1.55 log cd/m2, P=0.501) and median serum retinol concentrations (0.95 vs 0.93 µmol/l, P=0.734) were not significantly different in cases and controls either overall or in each population group. More restricted case definitions reduced the prevalence of reported XN to 5.5% (P<0.001), but there was still no significant difference between cases and controls although the results were in the expected direction. After treatment, the median serum retinol concentration improved significantly only in the most deficient group, the young children. Dark adaptation improved in all the subgroups but the difference was only significant for young children and primary school-age children when the restricted case definitions were used. CONCLUSIONS:: XN reports are a poor indicator of vitamin A deficiency in this population. SPONSORSHIP:: Task Force Sight and Life, Basel, Switzerland.European Journal of Clinical Nutrition (2004) 58, 409-419. doi:10.1038/sj.ejcn.1601797 [ABSTRACT FROM AUTHOR]

We propose a two algorithms for computation of (sharp) enclosures of definite interevals: a local adaptive algorithm (LAA) and a global adaptive algorithm (GAA). Both algorithms are based on Gauss-Legendre quadrature. Error terms are bounded using automatic differentiation in combination with interval evaluations. Several numerical examples are presented; these examples include comparison with an adaptive interval Romberg scheme. [ABSTRACT FROM AUTHOR]