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Abstract #18969 Published in IGR 3-1
The influence of contour line size and location on the reproducibility of topographic measurement with the Heidelberg Retina Tomograph
Roff EJ; Hosking SL; Barnes DAOphthalmic and Physiological Optics 2001; 21: 173-181
BACKGROUND: The recommended contour line (CL) location with the Heidelberg Retina Tomograph (HRT) is on the inner edge of Elschnig's scleral ring. This study investigated HRT parameter reproducibility when: (i) the CL size is altered relative to Elschnig's ring; (ii) the CL is either redrawn or imported between images. METHODS: Using the HRT, seven 10° images were acquired for ten normal volunteers and ten primary open-angle glaucoma (POAG) subjects. A CL was drawn on one image for each subject using Elschnig's scleral ring for reference and imported into subsequent images. The CL diameter was then (a) increased by 50 μm; (b) increased by 100 μm; and (c) decreased by 50 μm. To investigate the effect of the method of contour line transfer between images a CL was: (1) defined for one image and imported to six subsequent images; (2) drawn separately for each image. RESULTS: Parameter variability improved as the size of the CL increased for the normal group relative to Elschnig's ring but was unchanged in the POAG group. The export/import function (method 1) resulted in better parameter reproducibility than the redrawing method for both groups. CONCLUSIONS: The exporting and importing function resulted in better parameter variability for both subject groups and should be used for transferring CLs across images for the same subject. Increasing the overall CL size relative to Elschnig's scleral ring improved the reproducibility of the measured parameters in the normal group. No significant difference in parameter variability was observed for the POAG group. This suggests that the reproducibility of HRT images are affected more by the variation in topography between images than change in CL definition.
Dr E.J. Roff, Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
Classification:
2.14 Optic disc (Part of: 2 Anatomical structures in glaucoma)
