Repeatability and validity of lens densitometry measured with Scheimpflug imaging
Received 24 December 2008; received in revised form 25 March 2009; accepted 26 March 2009.
Purpose
To assess the repeatability and validity of lens densitometry derived from the Pentacam Scheimpflug imaging system.
Setting
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.
Conclusion
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.
From the School of Optometry (Kirkwood, Hendicott, Read), Queensland University of Technology, Brisbane, and the NH&MRC Centre for Clinical Eye Research (Pesudovs), Flinders University and Flinders Medical Centre, Adelaide, Australia
Corresponding author: Mr. Bradley Kirkwood, School of Optometry, Queensland University of Technology, Victoria Park Road, Kelvin Grove, Brisbane, 4059, Australia.
No author has a financial or proprietary interest in any material or method mentioned.
Supported in part by National Health and Medical Research Council Centre of Clinical Research Excellence Grant 264620, and the National Health and Medical Research Council Career Development Award 426765 (Dr. Pesudovs), Canberra, Australia.
Inez Hsing, Rebecca Cham, Kylie Phillis, and Laura Sims assisted in gathering and analyzing lens density metrics from the Scheimpflug system.
ABSTRACT