Visual Profile of Children who Passed or Failed the UK School Vision Screening Protocol

BACKGROUND: We applied the National Screening Committee vision screening protocol [pass criterion monocular acuity ≤ 0.2 LogMAR in both eyes(BE)] to children four to five years old to investigate the visual profile of children who passed/failed. Previous studies have only evaluated those failing. The aim was to derive false positive and negative values, specificity/sensitivity of the vision screening protocol for detecting significant visual defects (strabismus and/or significant refractive error) and the utility of a 'plus blur test' in identifying hyperopia. METHODS: Participants included 294 children (5.2 ± 0.4 yrs). In addition to the vision screening protocol (monocular acuity-3 m crowded Keeler LogMAR letters), acuities were recorded through +2.50D and +4.00D lenses and ocular alignment and cycloplegic refractive error were assessed. Using acuity measures, participants were classed as passing/failing the screening protocol. Each participant was also classed as having a strabismus and/or significant refractive error (hyperopia ≥ +4.00DS; myopia ≤ -0.50DS; astigmatism ≤ -1.50DC; anisometropia ≥ +1.50DS) or no significant visual defects. RESULTS: Of the 284 children who completed all tests, 27.8% failed to achieve 0.2 LogMAR in BE. The acuity pass/fail criterion had a sensitivity of 70.4% and specificity of 82.2% for detecting strabismus and/or significant refractive error. Of those who failed, 51.9% (n = 41/79) had no strabismus and/or significant refractive error (false positives). Of those who passed, 7.8% (n = 16/205) had visual defects (false negatives). The 'plus blur tests' improved sensitivity in detecting significant refractive error (+2.50D & +4.00D 90.7%) but significantly reduced specificity (+2.50D = 65.2%; +4.00D = 60.9%). CONCLUSIONS: School-entry vision screening is reasonably sensitive and specific for detecting strabismus and/or significant refractive error. Most children with visions poorer than 0.2 LogMAR need refractive intervention, and the majority of the remainder are likely false positives for significant visual defects. One in 13 children who pass have either strabismus and/or significant refractive error (7.8%). The inclusion of a 'plus blur test' was not a useful addition to the vision screening protocol.