Purpose: To assess whether a Valsalva manoeuver influences intra-ocular pressure (IOP), cerebrospinal fluid pressure (CSF-P) and, by a change in the trans-laminar cribrosa pressure difference, optic nerve head morphology. Methods: In the first part of the study, 20 neurological patients (study group 'A') underwent measurement of 1013 and lumbar CSF-P measurement in a lying position before and during a Valsalva manoeuver. In the second study part, 20 healthy subjects (study group 'B') underwent ocular tonometry and confocal scanning laser tomography of the optic nerve head before and during a Valsalva manoeuver. Results: During the Valsalva manoeuver in study group 'A', the increase in CSI-P P by 10.5 +/- 2.7 mmHg was significantly (p < 0.001) higher than the increase in IOP by 1.9 +/- 2.4 mmHg. The change in CSF-P was not significantly (p = 0.61) correlated with the change in It/P. During the Valsalva manoeuver in study group 'B', IOP increased by 4.5 +/- 4.2 mmHg and optic cup volume (p < 0.001), cup/disc area ratio (p = 0.02), cup/disc diameter ratio (p = 0.03) and maximum optic cup depth (p = 0.01) significantly decreased, while neuroretinal rim volume (p = 0.005) and mean retinal nerve fibre layer thickness (p = 0.02) significantly increased. Conclusions: The Valsalva manoeuver-associated short-term increase in CSILP was significantly larger than a simultaneous short-term increase in IOP. It led to a Valsalva manoeuver-associated decrease or reversal of the trans-laminar cribrosa pressure difference, which was associated with a change in the three-dimensional optic nerve head morphology: optic cup-related parameters decreased and neuroretinal rim-related parameters enlarged. These findings may be of interest for the pathogenesis of glaucomatous optic neuropathy.