The effect of an artificially elevated intraocular pressure on the central corneal curvature

Twenty-three optometry students with normal corneal condition were recruited. The intraocular pressure and central corneal curvature of the right eye were measured in a sitting and a 30 degrees head-down posture. The mean (standard deviation) IOPs before and during posture change were 15.6 (2.4) mmHg and 22.1 (2.3) mmHg respectively. This 6.5 mmHg mean rise in IOP was found to be statistically significant which is similar to the results from previous studies. The mean changes in radius of corneal curvature and the orientation of the axis of the vertical principal meridian were 0.02 mm (SD 0.025 mm) and 2.4 degrees (SD 10.4 degrees) respectively. No significant variation was demonstrated on these keratometric results due to the 30 degrees head-down posture. The maximum change in radius of curvature was only 0.055 mm for one subject. Perhaps this amount of pressure rise was not sufficient enough to distort the corneal surface centrally. Another possibility could be an even distribution of the elevated pressure around the cornea, or the distribution of pressure is not even but could not be revealed by a conventional keratometer.