Repeatability and effects of sequential measurements with POBF Tonograph

(1) To investigate the effect of performing sequential measurements using a Pulsatile Ocular Blood Flow (POBF) Tonograph on POBF and intraocular pressure (IOP) measurements; (2) to determine any effect on IOP caused by performing POBF measurements on the fellow eye; and (3) to assess repeatability of measurements obtained using the POBF Tonograph. Forty-six normal adult subjects (13 men, 33 women; age range, 18 to 55 years) took part in the present study. Twenty-one subjects underwent sequential measurements with a POBF Tonograph on five different occasions with five different time intervals (1, 2, 5, 10, and 15 minutes) between recordings. Twenty subjects underwent a baseline measurement on one eye with the POBF Tonograph, followed by repeat measurements in both eyes after 15 minutes. An additional 25 subjects underwent sequential measurements on the same eye with an interval of 15 minutes between readings. The intraclass correlation coefficient and Bland-Altman plots were used to assess repeatability of the instrument for all 46 subjects for the 15-minute time interval. In all the groups, repeated measurement resulted in a lower recorded IOP. A multivariate analysis of variance indicated that there was a significant decrease in IOP when measurements were repeated within 15 minutes (p=0.024), but there was no significant change in the POBF values (p=0.76). The recorded IOP was significantly lower when sequential measurements were performed with an interval of 1 minute (p