Although it has been known for many years that in anisometropia there exists a difference in the sizes of the two retinal images and that in the higher degrees of anisometropia, especially aphakia, binocular vision is impossible, it remained for the recent work of Ames and his associates on aniseikonia to reveal the importance of small differences in the sizes of the two retinal images. Thus, Madigan1 stated: "The average difference in size of retinal images in normal persons free from symptoms was found to be 0.53 per cent. The average difference in size of retinal images in patients with symptoms was 1.53 per cent. . . . Relief from symptoms has been obtained following the correction of disparity in size of retinal images as low as 0.75 per cent." Ames2 stated: "It can be demonstrated that binocular vision is practically impossible with aniseikonia of more than 4