Comparison of Parameters from Heidelberg Retina Tomographs 2 and 3
Presented at: Association for Research in Vision and Ophthalmology Annual Meeting, May 2006, Ft. Lauderdale, Florida.
Received 24 January 2006; received in revised form 25 May 2007; accepted 25 May 2007. published online 28 August 2007.
Purpose
To compare stereometric parameters and classification results from the Heidelberg Retina Tomograph version 2 (HRT2); HRT3; and HRT3 Glaucoma Probability Score (GPS), an automated method of obtaining optic nerve head analysis without the need for manual definition of disc margin.
Design
Retrospective cross-sectional study.
Participants
Five hundred four eyes from 281 consecutive subjects (glaucoma, glaucoma suspect, and healthy) evaluated in a glaucoma clinic.
Methods
All participants had HRT2 scanning of the optic nerve head. Inclusion criteria were scans with good centration and focus, even illumination, an overall quality score by HRT3 of acceptable or better, and standard deviation < 50 μm. A Bland–Altman analysis was used for the comparison of HRT2 and HRT3. From these results, calibration equations were determined to permit conversion of the measurements between devices. The agreement between HRT2 and HRT3 Moorfields regression analysis (MRA) and HRT3 GPS classification methods was measured using κ statistics.
Main Outcome Measures
Heidelberg Retina Tomograph version 2 and HRT3 stereometric parameters, MRA, and global GPS.
Results
There was a statistically significant difference between HRT2 and HRT3 global disc area, rim area, cup area, rim volume, cup volume, height variation contour, and retinal nerve fiber layer cross-sectional area stereometric parameters. All of those parameters were smaller using HRT3, due to a manufacturer-reported horizontal scaling error of 4% in HRT2 that was corrected in HRT3. κs for agreement were 0.60 between classifications (within normal limits, borderline, and outside normal limits) of MRA by HRT2 and HRT3 and 0.47 between HRT3 MRA and GPS.
Conclusions
The HRT3 generally provided smaller stereometric disc measurements than HRT2. There was no clear conversion between HRT3 and GPS parameters, as the 2 methods for measuring the stereometric parameters differ.
Available online: August 27, 2007.
University of Pittsburgh Medical Center Eye Center, Eye and Ear Institute, Ophthalmology and Visual Science Research Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
Correspondence to Gadi Wollstein, MD, UPMC Eye Center, Department of Ophthalmology, University of Pittsburgh School of Medicine, 203 Lothrop Street, Eye and Ear Institute, Suite 834, Pittsburgh, PA 15213.
Manuscript no. 2007-108.
Supported in part by the National Institutes of Health, Bethesda, Maryland (grant nos. RO1-EY013178-6, P30-EY008098); Eye and Ear Foundation, Pittsburgh, Pennsylvania; and Research to Prevent Blindness, Inc., New York, New York (unrestricted grant).
Dr Schuman receives royalties for intellectual property licensed by Massachusetts Institute of Technology to Carl Zeiss Meditec, Inc.
ABSTRACT