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Abstract #21778 Published in IGR 10-3

Analysis of HRT images: Comparison of reference planes

Poli A; Strouthidis NG; Ho TA; Garway-Heath DF
Investigative Ophthalmology and Visual Science 2008; 49: 3970-3975

See also comment(s) by Linda Zangwill


PURPOSE: The values of Heidelberg Retinal Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) stereometric parameters depend on the reference plane (RP), the instability of which results in parameter variability. Identification of change depends on RP stability. This study was undertaken to evaluate the influence of various RPs on rim areas (RAs) in a longitudinal image series. METHODS: A longitudinal image series of 31 subjects with ocular hypertension who had reproducible visual field loss and 19 normal subjects was analyzed using five different RPs: the standard RP (HRT software version 3.1.2.0), two 320-μm RPs (software ver. 3.1.2.0 and 1.7.0), a previously described experimental RP, and a new Moorfields RP. The Moorfields RP takes the standard RP at baseline and then is fixed relative to the reference ring for subsequent images. Linear regression of RA over time was performed, and the slope and residual SD (RSD) were calculated for each RP. Comparisons between RPs were made by paired t-tests. RESULTS: In eyes with progressing disease, application of the standard RP resulted in significantly greater variability (as measured by the RSD) compared with other RPs (mean 0.057 2 vs. 0.035-0.038 2). There was a trend toward faster RA change/time (mean, -0.0123 2/y) for the standard RP and slower (-0.0095 2/y) for the experimental RP. There was a trend for the Moorfields RP to result in the best signal-to-noise ratio (speed of RA change/variability): mean RA slope -0.0118 2/y and mean global RSD 0.0372. CONCLUSIONS: Compared to the standard RP, the Moorfields RP has significantly lower variability and probably provides a greater facility for discriminating RA change from measurement variability in a longitudinal HRT image series.

Dr. A. Poli, National Institute for Health Research Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS (National Health Service) Foundation Trust and the UCL Institute for Ophthalmology, London, UK


Classification:

6.9.1.1 Confocal Scanning Laser Ophthalmoscopy (Part of: 6 Clinical examination methods > 6.9 Computerized image analysis > 6.9.1 Laser scanning)



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