Comparison of line and space bisection in evaluation of normal and amblyopic spatial vision

Background: Partitioning experiments have been used historically and in the recent past to evaluate space perception in visually normal and disturbed individuals. Specifically, amblyopic patients display notably distorted and/or uncertain spatial localization when assessed by either line or space bisection. Methods: This investigation was concerned with the comparison of line bisection with space bisection. Normal and amblyopic subjects bisected horizontal lines and spaces extending 1, 2, 3 and 15 deg are monocularly on a computer screen. Results of the two procedures were compared. Results: Visually normal subjects bisected both lines and spaces without reproducible distortion, within uncertainties approximating 1-3% of their length. No differences were observed between the two procedures. Strabismic amblyopes bisected without constant distortion to either side of the geometrical mean, irrespective of direction or extent of the deviation; their uncertainty at bisecting ranged from 2% to 12%. Again, no distinction between line and space bisection could be made. Conclusion: We conclude that the two procedures yield comparable results.