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M. Frazier, P. S. W. Fuhr, W. L. Marsh-Tootle; Evaluation of a Pilot Project to Screen Children’s Vision in Nicaragua. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4836.
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The purpose of this study was to evaluate visual acuity screening administered by local teachers and nurses in Nicaragua.
Local teachers and nurses were trained by experts to screen young children using a standard protocol and testing at 5 feet with a booklet containing 12 Lea symbols. Each page had a single, 20/40 symbol surrounded by bars separated by one half the target width. Fail criterion was two or more incorrect answers per binocular or monocular assessment. Optometrists, who were masked to the screening result, performed a standardized examination with cycloplegia on a selected sample of 365 children that included both screening passes and fails. Diagnostic fails were determined by the doctor's decision to treat or monitor the child's condition.
Children were in pre-school to second grade (aged 3 to 9 years). Of the 5,673 children who were screened, 350 (6.17%) failed the screening. The sample of children examined included 211 screening passes and 154 fails. Sensitivity was 77%, and specificity was 66%. Specificity was reduced by a high false positive rate (28%) consistent with a low positive predictive value (34%). The false negative rate (4%) was consistent with a high negative predictive value (94%).
The false positive rate of this protocol, as implemented by local teachers and nurses, was unexpectedly high and unacceptable. Efforts to decrease over-referrals may include further training and evaluation of screeners and /or implementing a second screening by a supervisor prior to recommending eye examinations. On the other hand, the false negative rate was low, and continued efforts to improve this program are essential to provide necessary eye care to children in this poverty stricken nation with limited manpower and resources. Other, more costly screening methods would not be feasible.
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