When axial anisometropia is corrected by spectacles, retinal image sizes are approximately equal; if contact lenses were to be used, the myopic eye would have the larger retinal image. Clinical tests measuring aniseikonia with spectacle lenses and with contact lenses do not show the aniseikonia to be related to the expected retinal image size, but show that there is less aniseikonia with contact lenses than with spectacle lenses. It is supposed that the reason for this lack of cotrelation is that the more myopic eye is stretched at the posterior pole. Thus a larger retinal image stimulates the comparative number of receptors as a smaller retinal image of a less myopic eye.