The rise and fall of intra-ocular pressure: the influence of physiological factors.

A number of physiological factors can influence the intra-ocular pressure of patients with normal, healthy eyes leading to the misinterpretation of tonometric findings. The influence and duration of four commonly encountered factors--drinking water, coffee, alcohol, and exercise--were investigated employing a non-contact tonometer. Drinking 1 litre of water increased the IOP for up to 140 min with a mean maximum increase of 4.4 mmHg. A similar change was induced by coffee, the increase lasting up to 95 min and displaying a mean maximum increase of 4.0 mmHg. The intra-ocular pressure fell with alcohol consumption by a maximum of 3.7 mmHg, regaining pre-test values in all subjects after 65 min. Vigorous exercise produced an immediate fall in mean intra-ocular pressure of 4.3 mmHg, initial pressure being restored in all subjects after 65 min. The impact of such factors upon normal physiology are discussed together with the implications for routine tonometry.