Aniseikonia:A Survey of Literature 1963‐64*

Abstract

Summary Contributions to the study of aniseikonia are discussed from a clinical, frankly partisan, point of view. The surveyed material includes textbooks on refraction and contact lens practice, research papers special reports and higher degree theses. The approach of conventional textbooks to aniseikonia is shown to lack vigour in physiological optics. Therapeutic aims are limited to standard visual acuity and a semblance of binocular vision, ignoring space perception almost completely. The orthodox approach to aniseikonia devised by Ogle and others, was an attempt to reorganise visual perception on the basis of the innate system of retinal correspondence. This aim conflicts with clinical experience, which shows that patients are able to acquire correct spatial orientation through experience. As an alternative the Optometrie Extension Programme endeavoured to apply the learning theory of behaviour to the care of visual space perception. So far this approach has not recognised the importance of safeguarding the established visual orientation with properly designed spectacle lenses. Present trends in aniseikonia show a differentiation into specialised applications. In strabismus, it is being gradually recognised that full correction of aniseikonia is desirable. Here the orthodox method of Ogle would be eminently suitable. However, the Space Eikonometer is often useless in cases of strabismus, owing to low stereoscopic acuity. Research is in progress with the aim of developing new methods for the measurement of aniseikonia. Anisometropia is another well defined field of specialised application. The source of the disturbance is the aniseikonia induced by spectacle lenses. Contact lenses and special spectacle lenses are being used successfully to correct the induced aniseikonia, while leaving the inherent aniseikonia unchanged. For the application of these lenses there is no need to measure the aniseikonia. It would seem that even in routine practice, by using relatively simple techniques and readily available materials, the care devoted to aniseikonic problems could be greatly improved. However, the long neglect of aniseikonia may be seen as being only one aspect of the general low standard of care devoted to the visual space sense. There are obvious implications in this for academic, clinical and professional training, especially in optometry.