Intrasession and Intersession Variabilities of Intraocular Pressure Measured by Noncontact Tonometer in Normal Volunteers

PURPOSE: Intraocular pressure (IOP) measured using a noncontact tonometer is evaluated by performing multiple measurements because IOP is affected by the ocular pulse. We investigated the relationship between value fluctuations in multiple measurements during noncontact tonometer measurements and cardiac rate. MATERIALS AND METHODS: Forty-two healthy subjects were included and IOP was measured using a noncontact tonometer. The measurement was performed three times each for the right eye and the left eye, for a total of six times. Blood pressure and cardiac rate were measured at the same time as the IOP measurement. Using repeated-measures analysis of variance, we examined whether the measured IOP and cardiac rate fluctuate throughout the day over the course of 4 days. RESULTS: There was a fluctuation in the IOP in a sequence only on day 1 of the four measurement days (P < 0.001). The IOP on day 1 tended to be high for the first and second measurements (P = 0.0111–0.0015). Systolic blood pressure and diastolic blood pressure did not fluctuate over the 4 days (P = 0.6247 and 0.7132), but cardiac rate was high only on day 1 (P = 0.0276). CONCLUSION: The IOP on day 1 tended to be high in the first and second measurements. The IOP measured on days 2–4 did not fluctuate during the sequence of measurements. The cardiac rate measured at the same time as the IOP was high only on the first day.