Direct recordings were made of intraocular pressure fluctuations during volitional activity in a human volunteer prior to enucleation for ocular tumor. Pressure increments of the order of 90 mm Hg for squeezing of lids, 10 mm Hg for eye turned to the side, and 10 mm Hg for blinking were recorded. Accommodation was attempted despite preoperative cycloplegia and revealed pressure increments of 4 mm Hg followed by a decrement of pressure.
Coleman DJ, Trokel S. Direct-Recorded Intraocular Pressure Variations in a Human Subject. Arch Ophthalmol. 1969;82(5):637-640. doi:10.1001/archopht.1969.00990020633011