Intermittent excavation of the optic disc, which was associated with fluctuations of the intraocular pressure, was observed in an eye with open-angle glaucoma over a period of two weeks. As long as the excavation was readily reversible, the visual field was normal. Glaucomatous excavation in this case appeared to be due to weakening of the supporting tissue of the nerve head as a result of direct mechanical pressure. Intermittent excavation of the optic disc may precede permanent excavation in other cases of glaucoma, but the phenomenon is unlikely to be observed because of its transitory nature.
Neumann E, Hyams SW. Intermittent Glaucomatous Excavation. Arch Ophthalmol. 1973;90(1):64-66. doi:10.1001/archopht.1973.01000050066014