Interobserver agreement of Heidelberg Retina Tomograph parameters

Purpose: To measure the interobserver agreement of Heidelberg Retina Tomogr aph (HRT; Heidelberg Engineering, Heidelberg, Germany) parameters as a resu lt of different observers' contour line placements. Methods: The optic nerve heads of 50 patients with glaucoma were imaged wit h 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, a nd there was no formal discussion as to where to place the contour line. Th e following stereometric parameters were calculated for each image for each observer: disc area, mean height of contour, cup shape, rim volume using t he standard reference plane from software version 1.11 rim volume using a r eference plane of 320 mu m below the retinal plane, and volume above curved surface. Agreement between the five observers was tested for each paramete r 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), Agreemen t was almost perfect for mean height of contour (ICC = 0.94), cup shape (IC C = 0.92), and volume above curved surface (ICC = 0.83). Conclusion: The interobserver agreement for the HRT parameters was substant ial to almost perfect, indicating that the HRT results as defined by the fi ve observers were interchangeable.