Effectiveness of the Lea Symbols and Random Dot E in a large preschool vision screening program

Abstract

Introduction: In 2001 the Maternal Child Health Bureau/National Eye Institute Vision Screening (MCHB/NEI) Task Force developed interim recommendations for preschool vision screening. This study sought to define the positive-predictive value of these recommendations in a statewide vision screening program using the Lea Symbols (LS) and Random Dot E (RDE). Methods: With IRB approval, the Vision Initiative for Children (VIC) developed a vision screening training program incorporating the MCHB/NEI recommendations to certify, equip, and support community preschool vision screeners. Acuity testing was conducted with the LS at a critical line of 20/40 for 3-year-olds and 20/30 for 4-year-olds. RDE stereoacuity was done at 40 cm (630 arcsec). Results: Since 2001 the VIC Program has certified 978 lay screeners. 15,267 screening results have been reported on children 36 to 59 months of age. 2841 children failed the vision screen and were referred to a local optometrist or ophthalmologist for examination. 345 examination results were received and reviewed. 55 children (16%) had amblyopia. An additional 176 children (51%) had a significant amblyogenic condition or refractive error sufficient for glasses. The overall positive-predictive value (PPV) was 67%. Discussion: The PPV for screening tests used by trained lay screeners in this study compares favorably to the PPV of 31% for the Welch-Allen SureSight autorefractor and is similar or low compared with the PPV of 66 to 92% for the MTI Photoscreener. Conclusions: Traditional screening with the LS and the RDE achieves a PPV of 67% when used by certified lay screeners and remains a reasonable, inexpensive method for use in large screening programs. Adjusting the passing criteria for one or both of these tests may enhance the PPV, but at the risk of increasing the false-negative value.