Diagnosis accuracy of two vision screeners for visual health surveillance of workers who use video display terminals

OBJECTIVE To compare the diagnostic accuracy of two vision screeners by a visual examination performed by an optometrist (gold standard) and to evaluate the concordance between both screeners and between each screener and the gold standard. METHODS This was a cross-sectional study that included computer workers who attended a routine yearly health examination. The study included administrative office workers (n=91) aged 50.2±7.9 years (mean±standard deviation), 69.2% of whom were women and 68.1% of whom used video display terminals (VDT) for >4 h/day. The routine visual examination included monocular and binocular distance visual acuity (VA), distance and near lateral phoria (LP), stereo acuity (SA), and color vision. Tests were repeated with Optec 6500 (by Stereo Optical) and Visiotest (by Essilor) screeners. Sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV), and false positive and negative rates were calculated. Kappa coefficient (κ) was used to measure the concordance of the screeners and the gold standard. RESULTS The sensitivity and specificity for monocular VA were over 80% for both vision screeners; PPV was below 25%. Sensitivity and specificity were lower for SA (55%-70%), PPV was 50%, and NPV was 75% for both screeners. For distance LP, sensitivity and PPV were <10% in both cases. The screeners differed in their values for near LP: Optec 6500 had higher sensitivity (43.5%), PPV (37.0%), and NPV (79.7%); whereas the Visiotest had higher specificity (83.8%). For color vision, Visiotest showed low sensitivity, low PPV, and high specificity. Visiotest obtained false positive rates that were lower or similar to Optec 6500, and both screeners obtained false negative rates below 50%. Both screeners showed poor concordance (κ<0.40). CONCLUSIONS A high value for NPV would qualify both screeners as acceptable alternatives for visual health surveillance when used as a screening tool; patients with positive test results should be referred to a specialist.