Comparison of optic nerve head topography in normal eyes using confocal laser scanning tomograph and retinal thickness analyzer
Abstract
Background: To compare optic nerve head topography measurements by Heidelberg retina tomograph I (HRT) and retinal thickness analyser (RTA) and thereby to determine clinical agreement between the devices. To investigate reproducibility of measurements for HRT and RTA. To obtain our own HRT and RTA database for comparison of healthy and glaucomatous eyes.
Methods: The study included 100 normal eyes of 50 white adults of both sexes (mean age of 55.5 [SD 9.5] years). Ophthalmologic examination, fundus photography, HRT and RTA examinations were performed. To determine reproducibility 10 volunteers repeated the examination after a week. For HRT and RTA measurements mean (SD), median, 5th and 95th percentile, range and coefficient of variation were calculated. Differences in topographic parameters between HRT and RTA were tested for significance. Clinical agreement was assessed with »limits of agreement« and reproducibility expressed by repeatability coefficient and intraclass correlation coefficient (ICC).
Results: Significant differences (p < 0.05) in topographic parameters obtained by HRT and RTA were observed for all parameters except for rim area (p = 0.051) and height variation contour (p = 0.054). Limits of agreement between HRT and RTA were too wide and clinically important. Repeatability coefficient was good (< 0.10) for all HRT parameters except for RNFL cross-sectional area (0.28). Repeatability coefficient was > 0.10 for RTA parameters cup area (0.15), rim area (0.19), maximum cup depth (0.13), height variation contour (0.11) and RNFL cross-sectional area (0.14). ICC was good (> 90%) for all parameters, except for mean RNFL thickness (89%) for HRT and height variation contour (84%) for RTA.
Conclusions: The two devices cannot be used interchangeably. At present, clinical usefulness of HRT is superior to RTA due to better reproducibility of measurements, better software support, shorter duration of the examination and good comparability of our HRT database with the database included in the latest HRT software version. At the moment RTA is using the same database as HRT. Therefore, our RTA database provides a new basis for comparison of optic disc characteristics between healthy and glaucomatous eyes.
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