Firstly, the more distinctive features of the morphology and semeiology of the normal optic disk and peripapillary region are discussed. The authors then outline the principal morphological and functional characteristics of glaucomatous optic neuropathies. An appropriate description of the optic disorders which may resemble glaucoma follows. This section reviews separately the vascular disorders considered the most significant from the point of view of frequency and clinical scope, and non-vascular disorders of a heterogeneous nature (toxic, inflammatory, degenerative, malformative and compressive). Finally, the dangers of diagnostic confusion in such cases are mentioned and the most pertinent clinical characteristics for the differentiation between glaucomatous and glaucomatous-like forms are discussed.