title: Laser vs ultrasound biometry--a study of intra- and interobserver variability.
abstract: BACKGROUND
  Accurate biometry is of vital importance in achieving predictable postoperative refraction following cataract surgery.
  
  
  OBJECTIVE
  To evaluate the accuracy and consistency in biometry, achieved by the new generation laser biometric system in comparison with the ultrasound biometric system.
  
  
  METHODS
  The study was randomized and prospective. Biometry was performed in 68 eyes of 39 patients by three groups of biometrists (expert, intermediate user, novice). Expert and intermediate users are compared as group A, and expert and novice are compared in group B. Axial length, anterior chamber depth (ACD), and keratometry results are compared by t-test analysis.
  
  
  RESULTS
  Axial length measurement variation between expert and non experts was 10 times less using laser than ultrasound (P<0.001). ACD measurement variation was also significantly less when using laser compared to ultrasound (P=0.003). Need for some level of user training is indicated in ACD measurement since group A achieved more consistent readings than group B. Keratometry measurements on the laser system were unreliable due to high range of results. Biometric failure was seen in 12% of eyes undergoing laser and 1% undergoing ultrasound biometry.
  
  
  CONCLUSIONS
  Axial length determination by laser biometry is more accurate and consistent at all levels of biometrist expertise, compared to ultrasound biometry. ACD and keratometry measurements on the laser systems need some degree of user training in order to produce consistent results.
authors.affiliation: Department of Ophthalmology, Dewsbury District Hospital, Dewsbury, UK. sidgoel@hotmail.com
authors.forename: S
authors.initials: S
authors.lastname: Goel
authors.forename: C
authors.initials: C
authors.lastname: Chua
authors.forename: M
authors.initials: M
authors.lastname: Butcher
authors.forename: C A
authors.initials: CA
authors.lastname: Jones
authors.forename: P
authors.initials: P
authors.lastname: Bagga
authors.forename: S
authors.initials: S
authors.lastname: Kotta
mesh_terms: D000328:Adult; D000368:Aged; D000867:Anterior Chamber / Q000473:pathology; D002387:Cataract Extraction; D002983:Clinical Competence; D003315:Cornea / Q000473:pathology; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation; D005123:Eye / Q000473:pathology*; D006801:Humans; D007834:Lasers; D008875:Middle Aged; D015588:Observer Variation; D011184:Postoperative Period; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D014465:Ultrasonics