Limits on improving the positive predictive value of the Welch Allyn SureSight for preschool vision screening.

PURPOSE: To describe our experience using the Welch Allyn SureSight (Welch Allyn, Inc., Skaneateles Falls, NY) when vision screening a large population of preschool children. Additionally, we explore the usefulness of altering referral criteria to create high specificity for remote field screening in instances in which over-referral is costly. METHODS: Preschool children were screened for amblyogenic factors with the SureSight. Referred children received a gold standard examination with American Association for Pediatric Ophthalmology and Strabismus Vision Screening Committee-established failure criteria. Referral criteria were made increasingly more stringent to lower the rate of referral, and the effect on positive predictive value (PPV) was determined. RESULTS: A total of 15,749 children were screened, with reliable screening obtained in >99%. Rowatt-modified Vision in Preschoolers Study referral criteria produced a referral rate of 7.3% and a PPV of 48.2%. The PPV was >70% for children with unreliable screenings and with estimated refractive errors exceeding the instrument's range. Altering referral criteria improved PPV until referral rate reached 4% (PPV approximately 64%); further refinement past this level did not increase PPV and, hence, inappropriately limited sensitivity. CONCLUSIONS: A good test instrument should have high PPV and a referral rate approaching the population disease. Although altering referral criteria to decrease referral rate also decreases sensitivity, it should improve PPV. The presence of an asymptotic limit to PPV means additional improvement in PPV cannot be obtained with this technology. Thus, SureSight's usefulness for high-specificity screening is limited; however, the current referral criteria are sufficient for large screening programs and provide an acceptable referral rate and PPV.

Field evaluation of the Welch Allyn SureSight vision screener: incorporating the vision in preschoolers study recommendations.

INTRODUCTION: The prospective Vision in Preschoolers (VIP) study evaluated 11 methods of screening and proposed referral criteria for the Welch Allyn SureSight(trade mark) Vision Screener with 90% and 94% specificity. The SureSight had a higher sensitivity than most other screening techniques when these criteria were applied. We evaluated the usefulness of these criteria in a field study of healthy preschool children. METHODS: The SureSight software was altered to recommend referral using the VIP referral criteria with 90% specificity. Lions Club volunteers screened preschool children throughout Tennessee. Referred children underwent comprehensive eye examinations with cycloplegic refraction. Examination failure criteria were based upon published standards. Reanalysis using the 94% specificity criteria was then performed. Outcomes included referral rate and positive predictive value. RESULTS: The SureSight was used to screen 4,733 children, and screening was successful in 99.7% of children. The referral rate using the 90% specificity criteria was 12.2%. Most children (73%) were referred for suspected astigmatism. The positive predictive value was 30%. Using the 94% specificity criteria from the VIP study decreased the referral rate to 7.9% and substantially decreased over referral for suspected astigmatism; however, several anisometropes went undetected. Higher specificity was achieved by raising astigmatism referral criteria to 2.2 diopters while leaving the anisometropia criteria unchanged. CONCLUSIONS: The SureSight can be used successfully for preschool screening in the field provided that criteria with high specificity are incorporated into the instrument's software program. Higher rates of positive predictive value can be achieved without jeopardizing sensitivity by raising astigmatism referral criteria to 2.2 diopters.