A clinical evaluation of random dot stereoacuity cards in infants

Purpose. To clinically evaluate the random dot stereoacuity cards developed by Birch and Salomao on a population of infants within the first 12 months of life and to generate baseline normative data. Methods. Random dot stereoacuity cards were constructed using vectographic vertical bar stimuli with cross disparities ranging from 45 to 1735 seconds of arc (1.65 to 3.2 log seconds of arc). Wearing polarising goggles, infants were assessed using a two-alternative forced choice preferential looking staircase procedure. Success rate and stereoacuity values for performance as a function of age were evaluated. Results One hundred and seventy-seven tests were completed on 41 infants with ages ranging from 5 to 56 weeks. The random dot stereoacuity procedure was successful in 128 (72.3%) infants, success being dependent upon age. At 0-8 weeks of age, none of the infants produced a fixation preferance towards even the coarsest stereogram. The success rate increased to 50% at 9-16 weeks, 97% at 17-24 weeks, 93% at 25-36 weeks, dropping to 69% at 37-56 weeks due to increasing intolerance to the goggles. Stereopsis was not demonstrable in infants under 8 weeks of age. By 9-16 weeks the mean stereoacuity level was 2.91 log seconds of arc, further increasing to 2.53 at 17-24 weeks, reducing slightly to 2.65 at 25-36 weeks. At 37-56 weeks the mean stereoacuity value was recorded as 2.53 log seconds of arc. Conclusion. Our results indicate that the infant random dot stereoacuity cards provide a simple, quick and portable test for the clinical assessment of stereopsis in infants aged between 17 and 36 weeks, and should prove to be a useful clinical tool to monitor infants at risk of binocular vision disorders.