A comparison of the Digital Biometric Ruler-300 and Echo-oculometer-3000: a report of two hundred cases

Axial length measurements in 200 patients were performed with the Digital Biometric Ruler (DBR) and the Echo-oculometer with (Echo-osc) and without an oscilloscope (Echo). Measurements taken with the DBR and Echo-osc correlated better with each other than either did with the Echo measurements. In 32% of cases, the DBR and Echo-osc measurements differed by 0.4 mm or more, corresponding to a difference in predicted implant power of 1 diopter (D) or more. In 8% of cases, the measurements differed by 0.8 mm or more, corresponding to a difference in predicted implant power of 2D or more. In spite of these differences in axial length measurement in individual patients, intraocular lens implant power using the SRKTM formula, could be accurately predicted to within 1D of spectacle correction in 75% to 82% of cases, and to within 2D of spectacle correction in 94% to 98% of cases using either the DBR or Echo-osc measurements. Based on the poor correlation of the Echo axial length measurements to the other two, and the poorer implant power prediction accuracy, we do not recommend the use of the Echo-oculometer without an oscilloscope.