Amblyopic processing of positional information. Part II: Sensitivity to phase distortion.

Amblyopic sensitivities to spatial distortions of compound gratings and checker-board textures were studied. Iso-energy target signals were used by employing phase modulations which leave the stimulus power spectra unaltered. The non-amblyopic eyes of the 6 amplyopes tested showed supranormal sensitivities at 1 s exposure duration for both types of patterns. At 125 ms the amblyopic eyes were found virtually blind to the texture distortions while performance improved with prolonging the presentation time to 1 s. Comparable results were obtained with compound gratings. However, the correlation between amblyopic acuities and texture discrimination was higher than that between acuities and grating performance. This is probably due to the fact that both (misaligned) vernier targets and the texture are more 'natural' stimuli in the sense that they contain a broad range of spatial frequency components at many different orientations. Differences in behaviour between strabismic and anisometropic amblyopes did not occur. This suggests that the results depend upon defects of foveal visual function.