For the first time it was possible to compare perimetry during monocular and binocualr fixation under homogeneous conditions by the aid of phase-difference haploscopy. A binocular perimetry was not practicable using common perimeters. The examination was based on the anatomical fixed papilla nervi optici, which appears in the visual field as the blind spot. Its extension corresponds more to the anatomical size during binocular examination than during monocular examination. The difference is highly significant. Likewise the binocular perimetry refers to the quality of reproduction of paracentral retinal diseases significantly improved compared with the monocular examination. Supposing that the use of a larger fixation target during monocular perimetry contributes to the stabilization of normal eye movements, all examinations were additionally made with two fixation targets of different sizes. We have shown that there is no significant difference between the measurement either concerning the extension of the blind spot or the paracentral retinal diseases, which means a larger fixation target represents no fixation aid.