Stereoscopic and photogrammetric study of the disc cup in open-angle glaucoma reveals several morphological changes. The ovalisation of the cup, upwards, downwards or on the temporal side, appears early. It can be detected at the onset of the disease, even in the absence of visual field defects. It results in a localised thinning of the nervous rim, which is a characteristic sign of beginning glaucoma, but the depth of the cup is not increased even when perimetry already reveals important defects. The aim of this paper is to study, on the one hand, the morphological changes of the disc cup and on the other, the functional defects in open-angle glaucoma, and then to compare the results of the investigations.