Clinical Comparison of the Ocular Blood Flow Tonograph and the Goldmann Applanation Tonometer

Abstract

Purpose: To compare the IOP readings of an ocular blood flow (OBF) tonograph (OBF Labs UK Ltd) with Goldmann applanation tonometry. Methods: 194 patients were studied. In group 1, the software version 8.2 of the OBF tonograph was used in 214 eyes of 107 patients and in group 2, the 11.2 version of the tonograph was used in 174 eyes of 87 patients. Results: We found 63% of the OBF tonograph readings to be within ±2mm Hg of the Goldmann applanation tonometry readings in group 1 and 60% in group 2. In group 1 the correlation coefficient between the readings of the two instruments was 0.71 and 0.82 in group 2. The mean value for the paired differences in group 1 was –1.34±2.75mm Hg overall and –1.04±2.91mm Hg overall in group 2. There was a significant difference between the Goldmann applanation tonometer and OBF tonograph readings in the 8–10mm Hg interval (p0.1). Conclusions: The 11.2 version of the OBF tonograph is more accurate than the 8.2 version and measures IOP in a manner that corresponds well to the Goldmann applanation tonometer in the 8–10mm Hg and 21–29mm Hg intervals. It corresponds fairly well in the 11–20mm Hg interval.