Contact versus immersion biometry of axial length before cataract surgery

Abstract

Purpose: To compare the repeatability and agreement of contact and immersion ultrasound (US) biometry of axial length. Setting: Prince of Wales Hospital, Sydney, Australia. Methods: This prospective stratified randomized study comprised 36 patients with a preoperative refractive error less than 4.00 diopters (D) sphere or 2.00 D cylinder who were recruited before cataract surgery. Each of 3 operators measured both eyes of 12 patients by contact and immersion US techniques. A repeat measurement by both techniques was performed by the same operator in 6 cases and by a different operator in the other 6. Repeat and operator effects were examined. Results: The mean and standard deviation of the measurement sets were compared, and the differences between repeat measures were calculated. Axial length measurement was longer with the contact method than with immersion by 0.03 mm ( P = .04). The repeatability of the 2 techniques was similar. Conclusions: When the measurement set was repeated, the precision of contact US biometry was comparable to that of immersion, with no clinically significant difference in mean axial length measurements.