Preschool vision testing with a new device, the Scolatest.

To determine the reliability of results obtained in preschool children by school nurses with a new device for testing vision, the Scolatest, 153 children aged 4 to 5 years were presented with the Snellen E on the standard American Optical projector and with five letters of the Sheridan test (H, O, V, T and X) on the Scolatest. Another 212 children aged 3 to 4 years were presented with the Allen symbols on the projector and with the Pigassou symbols on the Scolatest. The tests with the projector were given at 6 m by an experienced pediatric orthoptist, those with the Scolatest at 2.5 m by a school nurse. The proportion of good responses was higher with the Pigassou symbols than with the Allen symbols. The results with the Sheridan letters and the Snellen E were similar up to 20/30; beyond 20/30 the Snellen E appeared unreliable. The four vision-testing systems were also presented by a school nurse at 2.5 m on the Scolatest to 102 children aged 4 to 5 years (Snellen E and the five Sheridan letters) and 80 children aged 3 to 4 years (Allen and Pigassou symbols). The proportions of good responses were more comparable. The results suggest that a working distance of 2.5 m should be used in testing vision in preschool children. Visual screening at this distance should test acuity beyond the 20/30 equivalence if results comparable to those at 20 feet with the 20/30 standard requirement are to be obtained.