BINOCULAR PROBLEMS BY ANISOPHORIA AND ANI SEIKONIA AFTER CATARACT-SURGERY

Background Cataract and refractive surgery aiming at emmetropia, runs the risk to induce binocular problems, e.g. asthenopia or diplopia. If the compatibility concerning binocularity is solely estimated by the calculation of the difference of the retinal image sizes, using intrao cular lens formulas or so-called ''aniseikonia-programs''. important p hysiological facts are not considered. The actual amount of the anisei konia. this is the difference of the image size which the patient perc eives subjectively, depends on 3 parameters: 1. the optically induced difference of the retinal image size, 2. the spatial densitiy of the r etinal photoreceptors and the size of the receptive fields, 3, a possi bly existing anomalous retinal correspondence for different retinal im age sizes. Besides aniseikonia, the induction of postoperative anisoph oria by the required spectacle correction is a considerable aspect. An iseikonia and anisophoria can cause fusional problems or diplopia beca use of the mentioned parameters and/or disparity of the retinal images . Case report Cataract surgery should reduce a monolateral high myopia , aiming emmetropia, in axial anisometropia. This resulted in one exem plary case in high aniseikonia with complaints, while in other, compar able patients only a small amount of aniseikonia could be measured by haploscopy. This preoperative refractive situation is comparable to re fractive surgery. In a second case with symmetrical myopia of -4 D, bi nocular problems with diplopia and asthenopia were induced after monol ateral cataract surgery by the combination of a moderate aniseikonia a nd anisophoria. Conclusions To predict the actual postoperative anisei konia it is necessary for the patient to wear a contact lens preoperat ively fur a short time to measure the aniseikonia by haploscopy, parti cularly prior to refractive surgery in axial length ametropia. Due to the different sizes of the receptive fields of the retina, different p ostoperative aniseikonias may result in spite of similar axial length anisometropia. The individual tolerance of an adult for a postoperativ ely created anisophoria is hardly predictable. It is obvious that the fusional stress ensued from aniseikonia and anisophora adds or multipl ies. In contrast to horizontal eye movements, vertical eye movements c an hardly be compensated by head movements, as the use of bi- or multi focals requires a down gaze of about 30 degrees. Here a height-balance -prism could help.