Journal of Medical Screening > Volume 15, Number 2 > Pp. 65-71

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Original Articles

Performance measures of the illiterate E-chart vision-screening test used in Northern District Israeli school children

Liora Ore, Deputy Medical Officer and Head of Department of Informatics  , Ministry of Health, Northern District, Nazareth Illit, Israel; School of Public Health, Haifa University, Haifa, Israel

Hanna J Garzozi, Head of Eye Department , Eye Department, Bnai Zion Medical Center, Haifa, Israel; Rappaport Faculty of Medicine, Technion, Haifa, Israel

Ada Tamir, Head of Statistical Unit , Department of Community Medicine and Epidemiology, Carmel Medical Center, Hafia, Israel; Rappaport Faculty of Medicine, Technion, Haifa, Israel

Nili Stein, Statistician , Department of Informatics, Ministry of Health, Northern District, Nazareth, Israel

Michal Cohen-Dar, Medical Officer , Ministry of Health, Northern District, Nazareth Illit, Israel; School of Public Health, Haifa University, Israel

Correspondence to: Dr Liora Ore, 3 Hamelacha Street, Nazareth Ilit 17000, Israel; liorao{at}netvision.net.il

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Objectives To evaluate the screening performance of 6/6 and 6/12 vision cut-offs with an illiterate E-chart implemented by a public health nurse to test children for ocular abnormalities and uncorrected refractive error. The gold standard diagnosis is an eye examination performed by an ophthalmologist.

Setting A cross-sectional population-based study was conducted among 2113 students' ages 6–7 and 13–14 years old in 70 Northern District Israeli schools.

Methods Students were tested by nurses and ophthalmologists. A nurse examination was carried out using the illiterate E-chart for vision measurement. The medical examination included vision history, clinical eye examination, vision and retinoscopy testing. The Physician's evaluation of whether students needed a referral for diagnostic procedures, treatment and/or follow-up was recorded. Screening test's performance was determined using ophthalmologist's decision regarding referral as the gold standard. Detection rate (DR), false-positive rate (FPR), odds affected positive result (OAPR), positive predictive value (PPV) and negative predictive value (NPV) were estimated overall and by students' demographic characteristics.

Results For vision >6/6 cut-off in at least one eye (eyes tested separately): DR – 71.9% (95% CI 65.8–78.7%), FPR – 22.8% (95% CI 17.9–28.9%), OAPR – 0.98:1 (95% CI 0.84:1–1.15:1), PPV – 52.7% (95% CI 45.4–61.2%), NPV – 90.9% (95% CI 88.7–93.1%). For 6/12 vision cut-off, namely vision 6/12 or worse in both eyes (tested separately): DR – 58.6 (95% CI 51.8–66.4%), FPR – 15.2% (95% CI 10.9–21.1%), OAPR – 1.13:1 (95% CI 0.94:1–1.35:1), PPV – 61.1% (95% CI 52.9–70.6%), NPV – 87.6% (95% CI 84.9–90.4%).

Conclusions Vision-screening test performance measures are mild. It is suggested to change vision cut-off level that denotes vision abnormality from current policy of vision not equal 6/6 in both eyes (tested separately) to vision 6/12 or worse in both eyes (tested separately). This change will result in reduction of FPR from 22% to 15%, concomitant with an increase in false-negative rate from 28% to 41%. Students may be equally screened by either a senior or a less experienced nurse.

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