title: Desktop auxiliary apparatus for A-scan ultrasound: repeatability and validity.
abstract: OBJECTIVE
  To evaluate the intraobserver repeatability and validity of biometric measurements with a newly developed auxiliary A-scan ultrasound apparatus at a rural clinic.
  
  
  METHODS
  Rural county hospital in China.
  
  
  METHODS
  Evaluation of diagnostic technology.
  
  
  METHODS
  Patients awaiting surgery for age-related cataract were consecutively enrolled for preoperative A-scan biometric measurements. The applanation A-scan was performed by 2 experienced nurses, with 1 using the conventional handheld method and the other using the new method with the auxiliary desktop apparatus. Two consecutive measurements were performed with each method. The 95% limits of agreement (LoA) and Bland-Altman plot were used to assess and compare the intersession measurement repeatability between the 2 methods.
  
  
  RESULTS
  Data for 75 eyes of 75 consecutive patients were available for analysis. The mean age of the patients was 74.3 years ± 7.4 (SD); 40.0% were men. The desktop method had a smaller standard deviation and coefficient of variance than the conventional handheld method for both measurement sessions. For intersession repeatability, the desktop method had a narrower 95% LoA range than the handheld method for all the biometry parameters. The axial length (AL) obtained with the desktop method was significantly longer than that with the handheld method (23.32 mm versus 23.14 mm; P<.01).
  
  
  CONCLUSIONS
  The newly developed auxiliary device had better intraobserver repeatability and more accurate AL measurements than the conventional handheld method, making it a better option for preoperative biometric measurement of cataract patients.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Hongfei
authors.initials: H
authors.lastname: Huang
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Ding
authors.forename: Decai
authors.initials: D
authors.lastname: Wang
authors.forename: Xiangfu
authors.initials: X
authors.lastname: Yang
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: Mingguang
authors.initials: M
authors.lastname: He
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058452:Axial Length, Eye / Q000033:anatomy & histology*; D001699:Biometry / Q000295:instrumentation*; D002681:China; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D004867:Equipment Design; D005260:Female; D006780:Hospitals, Rural; D006801:Humans; D019654:Lens Implantation, Intraocular; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D055095:Optics and Photonics / Q000295:instrumentation; D011300:Preoperative Care; D015203:Reproducibility of Results; D014463:Ultrasonography / Q000295:instrumentation*