Effect of third trimester of pregnancy on diurnal variation of ocular pressure.

This study was planned to evaluate the effect of pregnancy on diurnal variation of intraocular pressure (IOP) after placing control on all the IOP affecting factors. The IOP was measured with the Goldmann applanation tonometer. Both in the control and 3rd trimester subjects, the peak of mean IOP appeared in the morning when the subjects waked, and the trough of mean IOP happened at 2 am to 4 am. The diurnal intraocular pressure curves revealed that the IOP peaks were 15.4 +/- 0.9 and 12.9 +/- 0.6 mmHg in the control and third trimester pregnant subjects, respectively. Whereas the trough were 13.1 +/- 0.4 and 11.8 +/- 0.3 mmHg, respectively. The mean diurnal variation were 2.3 +/- 0.6 mmHg (P < 0.01), and 1.1 +/- 0.8 mmHg in the control and third trimester subjects, respectively. There are two main findings of present study: first, compared with non-pregnant control subjects, the IOP was significantly lower (P < 0.001) in the third trimester pregnant subjects. Second, in the third trimester of pregnancy, the lower IOP level was associated with the less degree of IOP fluctuations at various hours of the day.