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S. Wedner, C. Gilbert, H. Masanja, J. Todd; Screening and Treatment of Significant Refractive Errors in Tanzanian Secondary School Students . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1164.
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The Secondary School Eye Screening Study in Dar es Salaam, Tanzania explored components of a school screening programme, i.e. the validity of teachers’ screening for visual impairment, the validity of the +2D test to identify students with moderate hyperopia of >2D; attendance at a referral clinic (CCBRT), and wearing of free spectacles 3 months after their provision.
In July 2003, trained teachers screened year–1–students attending 14 randomly selected secondary schools in Dar es Salaam for bilateral poor visual acuity (VA) of <6/12, using Snellen’s E–charts. An eye team validated their performance 4 weeks later and also screened all students with bilateral good VA of >6/12 for moderate hyperopia by adding +2D lenses. The eye team referred students with poor VA in at least one eye and students with good VA after addition of +2D lenses to CCBRT, where they were refracted and their eyes examined. Students who needed spectacles were given them free and followed–up after 3 months to check whether they were being worn.
Of 3,988 students screened, 3.5% had uncorrected poor VA (<6/12 in one or both eyes), 3.3% had poor presenting VA and 1.2% still had poor VA with best correction. The sensitivity of teachers’ screening for bilateral impaired vision was moderate (75%), but the positive predictive value was poor (32%). The sensitivity of the +2D test was very good (100%), but the number of false positive referrals was high (PPV: 17%), which may partly be due to the low prevalence of moderate hyperopia (0.4%). 78% of referred students attended CCBRT. Students were more likely to attend if they lived with their mother (OR=36.9; p=0.02) and if they attended government schools (OR=33.3; p=0.02). 77 of 105 (73%) students who had been given spectacles were followed up at 3 months. Only 33% were wearing their spectacles, an additional 16% had them at school, 27% claimed that they had them at home and 25% said that they did not have them anymore.
Using teachers to test for visual deficits or introducing the +2D screening test for hyperopia are likely to increase the number of false referrals. The additional burden to eye services ought to be balanced against the benefit of using teachers for screening and of identifying students with moderate hyperopia. Similar studies are needed to explore the use of and reasons of non–use of spectacles in different cultural settings, as low compliance, as found in this Tanzanian study, makes the value of any screening programme questionable.
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