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Interobserver agreement of Heidelberg retina tomograph parameters
W V Hatch1, J G Flanagan, D E Williams-Lyn
1Glaucoma Research Unit, Toronto Western Hospital, Ontario, Canada.
Purpose:
To measure the interobserver agreement of Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) parameters as a result of different observers' contour line placement.
Methods:
The optic nerve heads of 50 patients with glaucoma were imaged with the HRT. Five observers traced each disc margin with a contour line. Each observer was masked to the contour line tracings of the other observers, and there was no formal discussion as to where to place the contour line. The following stereometric parameters were calculated for each image for each observer: disc area, mean height of contour, cup shape, rim volume using the standard reference plane from software version 1.11, rim volume using a reference plane of 320 microns below the retinal plane, and volume above curved surface. Agreement between the five observers was tested for each parameter using intraclass correlation coefficients (ICCs).
Results:
Interobserver agreement between the five observers was substantial for both rim volumes (ICC = 0.73) and for disc area (ICC = 0.67). Agreement was almost perfect for mean height of contour (ICC = 0.94), cup shape (ICC = 0.92), and volume above curved surface (ICC = 0.83).
Conclusion:
The interobserver agreement for the HRT parameters was substantial to almost perfect, indicating that the HRT results as defined by the five observers were interchangeable.