title: Repeatability and validity of lens densitometry measured with Scheimpflug imaging.
abstract: OBJECTIVE
  To assess the repeatability and validity of lens densitometry derived from the Pentacam Scheimpflug imaging system.
  
  
  METHODS
  Eye Clinic, Queensland University of Technology, Brisbane, Australia.
  
  
  METHODS
  This prospective cross-sectional study evaluated 1 eye of subjects with or without cataract. Scheimpflug measurements and slitlamp and retroillumination photographs were taken through a dilated pupil. Lenses were graded with the Lens Opacities Classification System III. Intraobserver and interobserver reliability of 3 observers performing 3 repeated Scheimpflug lens densitometry measurements each was assessed. Three lens densitometry metrics were evaluated: linear, for which a line was drawn through the visual axis and a mean lens densitometry value given; peak, which is the point at which lens densitometry is greatest on the densitogram; 3-dimensional (3D), in which a fixed, circular 3.0 mm area of the lens is selected and a mean lens densitometry value given. Bland and Altman analysis of repeatability for multiple measures was applied; results were reported as the repeatability coefficient and relative repeatability (RR).
  
  
  RESULTS
  Twenty eyes were evaluated. Repeatability was high. Overall, interobserver repeatability was marginally lower than intraobserver repeatability. The peak was the least reliable metric (RR 37.31%) and 3D, the most reliable (RR 5.88%). Intraobserver and interobserver lens densitometry values in the cataract group were slightly less repeatable than in the noncataract group.
  
  
  CONCLUSIONS
  The intraobserver and interobserver repeatability of Scheimpflug lens densitometry was high in eyes with cataract and eyes without cataract, which supports the use of automated lens density scoring using the Scheimpflug system evaluated in the study.
authors: School of Optometry, Queensland University of Technology, Brisbane, Australia. bradkirkwood@bigpond.com
authors: Bradley J
authors: BJ
authors: Kirkwood
authors: Peter L
authors: PL
authors: Hendicott
authors: Scott A
authors: SA
authors: Read
authors: Konrad
authors: K
authors: Pesudovs
mesh_terms: D000328:Adult; D000368:Aged; D001699:Biometry; D002386:Cataract / Q000145:classification*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010781:Photography / Q000592:standards*; D011446:Prospective Studies; D015203:Reproducibility of Results; D055815:Young Adult