The ocular tension of both eyes of 10 healthy, awake persons was measured during spontaneous, controlled hyperventilation (PACO2 mean value 23.6 Torr). Significant decreases in the ocular tension (P 2, and a correlation coefficient of r = ––0.30 for ocular tension and PaO2, and for ocular tension and pH (art.) a correlation coefficient of r = ––0.58.