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BackgroundTrichiasis is present when one or more eyelashes touches the eye. Uncorrected, it can cause blindness. Accurate estimates of numbers affected, and their geographical distribution, help guide resource allocation.MethodsWe obtained district-level trichiasis prevalence estimates for 44 endemic and previously-endemic countries. We used (1) the most recent data for a district, if more than one estimate was available; (2) age- and sex-standardized corrections of historic estimates, where raw data were available; (3) historic estimates adjusted using a mean adjustment factor for districts where raw data were unavailable; and (4) expert assessment of available data for districts for which no prevalence estimates were available.FindingsInternally age- and sex-standardized data represented 1,355 districts and contributed 662 thousand cases (95% confidence interval [CI] 324 thousand-1.1 million) to the global total. age- and sex-standardized district-level prevalence estimates differed from raw estimates by a mean factor of 0.45 (range 0.03-2.28). Previously non-standardized estimates for 398 districts, adjusted by ×0.45, contributed a further 411 thousand cases (95% CI 283-557 thousand). Eight countries retained previous estimates, contributing 848 thousand cases (95% CI 225 thousand-1.7 million). New expert assessments in 14 countries contributed 862 thousand cases (95% CI 228 thousand-1.7 million). The global trichiasis burden in 2016 was 2.8 million cases (95% CI 1.1-5.2 million).InterpretationThe 2016 estimate is lower than previous estimates, probably due to more and better data; scale-up of trichiasis management services; and reductions in incidence due to lower active trachoma prevalence.Author SummaryAs an individual with trichiasis blinks, the eyelashes abrade the cornea, which can lead to corneal opacity and blindness. Through high quality surgery, which involves correcting the position of the in-turned eyelid, it is possible to reduce the number of people with trichiasis. An accurate estimate of the number of persons with trichiasis and their geographical distribution are needed in order to effectively align resources for surgery and other necessary services. We obtained district-level trichiasis prevalence estimates for 44 endemic and previously-endemic countries. We used the most recently available data and expert assessments to estimate the global burden of trichiasis. We estimated that in 2016 the global burden was 2.8 million cases (95% CI 1.1-5.2 million).The 2016 estimate is lower than previous estimates, probably due to more and better data; scale-up of trichiasis management services; and reductions in incidence due to lower active trachoma prevalence.

Objective Vientiane Province is an urbanizing region in Southeast Asia. We aimed to determine the prevalence of refractive error and visual impairment in primary school–aged children in this region. Design Prospective, cross-sectional survey. Participants A total of 2899 schoolchildren from Vientiane Province, Lao People's Democratic Republic (Lao PDR). Methods Ten districts from Vientiane were randomly selected and 2 primary schools were randomly selected from each district. All children aged 6 to 11 years at selected schools were eligible to participate. The examination included visual acuity (VA) testing, cycloplegic retinoscopy with subjective refinement if indicated, ocular motility testing, and anterior segment and fundus examinations in visually impaired children. Main Outcome Measures Cycloplegic refraction and VA. Results There was an estimated total of 3330 children who were eligible to participate, and data were recorded from 2899 (87%) of these children. Complete refractive data were available on 2842 children (85% of eligible population). The mean spherical equivalent (SE) in the right eyes was +0.60 diopter (D) (95% confidence interval [CI], 0.49–0.72), and the mean SE in the left eyes was +0.59 (95% CI, 0.50–0.68). The prevalence of hyperopia was 2.8% (95% CI, 1.9–3.7; 88 subjects), and the prevalence of myopia was 0.8% (95% CI, 0.3–1.4; 24 subjects). The majority of children (98%; 95% CI, 97.0–99.0) had normal unaided binocular VA (at least 20/32 in their better eye). The overall prevalence of any visual impairment (presenting VA P = 0.001) was a significant predictor, and female gender ( P = 0.08) and Yao ethnicity ( P = 0.09) were borderline significant predictors of the presence of any visual impairment. Conclusions Visual impairment is not a public health concern in this primary school–aged population; however, visually impaired children in the community were not studied. From this baseline, future surveys could determine the effect of increasing urbanization on myopia prevalence in this population. Financial Disclosure(s) The author(s) have no proprietary or commercial interest in any materials discussed in this article.