title: Contact versus immersion biometry of axial length before cataract surgery.
abstract: OBJECTIVE
  To compare the repeatability and agreement of contact and immersion ultrasound (US) biometry of axial length.
  
  
  METHODS
  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.
authors.affiliation: Department of Ophthalmology, Prince of Wales Hospital, NSW 2031 Randwick, Australia. mhennes@bigpond.net.au
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hennessy
authors.lastname: Franzco
authors.forename: Derek G
authors.initials: DG
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000886:Anthropometry / Q000379:methods*; D001699:Biometry / Q000379:methods*; D002387:Cataract Extraction / Q000379:methods*; D005123:Eye / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D011446:Prospective Studies; D015203:Reproducibility of Results; D014463:Ultrasonography