Abstract
Abstract: :
Purpose: To demonstrate that most 3– to 5–year–old children will comply with the task requirements of a new objective preschool vision screener, the Ocular Vergence and Accommodation System (OVAS). Feasibility of this binocular, open view technology has previously been reported (Apple, HP and Hartmann, EE IOVS 2002;43:ARVO E–Abstract 1495). Methods: A human factors mockup of OVAS was constructed. Children looked through the unit at far and near accommodative targets displayed sequentially under computer control. The questions were: 1) would preschool children position themselves properly with respect to the faceplate, and 2) would they comply with the task requirements for up to 30 seconds? Two sessions, with 27 and 28 children respectively, were conducted. The first used only a far target (a quacking duck); the second session used the same far target and a dynamic near target (a finger–sized puppet moving from 66 cm to 33 cm). An ultrasound forehead transducer was used to evaluate appropriate positioning. One video camcorder recorded eye–tracking movements of the child; a second camcorder provided a profile view confirming positioning. Each child was asked to try the 30 second task three times. Slow motion videotapes were evaluated by expert reviewers, based on three criteria: 1) visibility of the pupils in the faceplate eyeholes; 2) confirmation via the eye–tracking video that the child was looking at the targets most of the time; and 3) that the child complied adequately during the 30 second test period. Results: In the first session, all 27 children complied with the task. In the second session, combining far and near targets, 27 of 28 children complied with the task requirements. Conclusions: The strategy of having children stand and look through the unit at the far and near targets is feasible. Preferred hand placement is the faceplate itself or periscope handles. Quick up/down positioning of the unit is mandatory to account for varying heights of children.
Keywords: screening for ambylopia and strabismus • strabismus: diagnosis and detection • eye movements: recording techniques