INTRODUCTIONThis prospective observational case series aimed to determine whether the lateral decubitus position, which is commonly adopted during sleep, has an effect on intraocular pressure (IOP) in normal controls.

METHODSPatients without glaucoma were recruited from those visiting outpatient clinics for non-glaucomatous conditions. The left eye of each patient was included. IOP was first measured using Tono-Pen® XL applanation tonometer in the supine position, following which a second measurement was immediately obtained for the left lateral head position. Measurements were obtained with the patient lying on one soft and one hard pillow for each position, and patients remained awake during these measurements. One tonometry reading was obtained for each position. Readings were recorded only when the average of four independent readings produced a statistical confidence index of 5%. Results were analysed using the paired Student's t-test for comparison of the means.

RESULTSIOP in the left lateral decubitus position (17.48 ± 3.18 mmHg) was significantly higher than in the supine position (14.48 ± 3.09 mmHg) when using soft pillows (p < 0.001). When hard pillows were used, IOP in the left lateral decubitus position also exceeded that measured in the supine position (16.65 ± 3.54 mmHg vs. 13.65 ± 3.58 mmHg; p < 0.001). There was no statistically significant difference in the IOPs measured for the same position when different kinds of pillows were used.

CONCLUSIONThe lateral decubitus position adopted during sleep is associated with changes in IOP in healthy volunteers.