To investigate the change in intraocular pressure (IOP) of normal healthy eyes at different positions while performing sit-ups.

Twenty normal healthy eyes of 20 subjects were studied. IOP was measured while in the 'sitting upright', 'supine', and 'head-down' position to determine postural effect on IOP when executing a sit-up. Measurements were taken after the performance of a sit-up and during the performance of a sit-up, in both the head up and head down positions to test the effect of the exercise on the IOP. In addition, the IOP after an 'isometric exercise with Valsalva's maneuver in the supine or head-down position' was measured to determine the actual IOP during a sit-up.

The postural change from sitting upright to tilting the head in a downward position caused the IOP to increase. After the performance of a sit-up, the IOP decreased in both the upright and supine positions, though IOP increased in the head-down position. After the isometric exercise with Valsalva's maneuver, IOP increased significantly regardless of position.

IOP increased significantly during sit-ups, but decreased afterward. Future studies should be performed to evaluate the long-term effects of IOP change during and after sit-ups with respect to the prognosis of glaucoma.