The present study examined how intraocular pressure is affected by changes in sleeping posture (22-2400 hours) from the sitting position to the supine, prone, and lateral positions in normal subjects.

Ophthalmological examination was performed on 140 eyes of 70 healthy adult men, and changes in the intraocular pressure were measured according to posture during sleep. The subject was initially relaxed and the base intraocular pressure was measured in the sitting position. In order to reduce the influence of intraocular pressure among the positions, namely, the supine, the prone, and the lateral recumbent positions, the subject was seated for ten minutes before assuming each position. Intraocular pressure was measured twice at 0 and 10 minutes in each position, and the mean of the two values was used for comparison.

Compared to the intraocular pressure in the sitting position, intraocular pressure increased significantly in the supine, prone, and lateral positions ( p < 0.05). Compared to the base intraocular pressure, the intraocular pressure measured in the prone position showed the largest difference, increasing 6.34 mm Hg in the right eye and 6.43 mm Hg in the left eye. The intraocular pressure measured in the lateral position was 3.62 mm Hg higher in the right eye and 3.63 mm Hg higher in the left eye, and that in the supine position was 2.42 mm Hg and 2.28 mm Hg higher in the right and left eyes, respectively.

The change in posture during sleeping from the sitting position to the supine, prone, and lateral positions caused increases in intraocular pressure in normal subjects. The results show that the change in sleeping posture induced by sleeping habits may raise intraocular pressure.