an abnormal condition, caused by astigmatism, in which contours of oblique orientation appear sharply focused whereas other orientations (vertical and horizontal) appear blurred, even when the astigmatism is optically corrected. This indicates that the astigmatism, prior to optical correction, altered orientation-selective mechanisms in the visual cortex in a direction favoring oblique over horizontal and vertical orientations. Presumably, individuals with meridional amblyopia have a paucity of cortical cells tuned to vertical and horizontal orientations.