Accuracy of Optic Disc Parameters Obtained by the Heidelberg Retina Tomograph in the Diagnosis of Glaucoma

Purpose: To determine which optic disc topographic parameters, obtained by the Heidelberg Retina Tomograph (HRT), are most useful to distinguish normal eyes from those with early to moderate glaucomatous visual field defects. Methods: From each of 92 normal subjects and 154 patients with primary open-angle glaucoma one randomly selected eye was studied. The Humphrey perimeter, program C 30-2 visual fields, and 13 HRT parameters (software 2.01, includes rim to disc area ratio) were utilized. Because some of the optic disc parameters depend on the optic disc area, these parameters were corrected for the effect of disc area. The total glaucoma group was divided into three subgroups according to the visual field defects: early (mean deviation (MD)>-6 dB, 65 eyes), moderate (MD -6 to -12 dB, 49 eyes), and severe (MD 1.60 dB), the sensitivity, specificity, accuracy, and areas under the receiver operating characteristic curve were, respectively: rim area (69%, 71%, 70%, 0.802), rim to disc area ratio (69%, 72%, 71%, 0.799), cup area (72%, 70%, 71%, 0.789) and cup to disc area ratio (69%, 70%, 69%, 0.790). In eyes with moderate glaucoma (MD = -8.751.88 dB), they were, respectively: rim area (78%, 86%, 83%, 0.872), rim to disc area ratio (76%, 86%, 82%, 0.869), cup area (76%, 87%, 83%, 0.864) and cup to disc area ratio (78%, 84%, 82%, 0.862). There was considerable overlap in HRT parameters between the normal and early glaucoma groups. Conclusions: The diagnostic value of single optic disc parameter had its limitations in the diagnosis of early stage glaucoma.