Sensitivity and specificity of Heidelberg Retinal Tomography II parameters in detecting early and moderate glaucomatous damage:: effect of disc size

To determine the efficacy of Heidelberg Retinal Tomography II (HRTII) parameters in differentiating normal eyes from eyes with early or moderate glaucomatous damage. HRTII tests were performed on 70 eyes of 70 patients with early or moderate glaucomatous damage, and 70 eyes of 70 healthy subjects. HRTII stereometric parameters, global and sectorial rim area parameters were recorded. Sensitivity and specificity of each parameter were calculated. Cases were divided into three groups according to disc size as large, medium and small, and mean values of parameters in glaucoma and control groups were compared. Mean disc area was larger in the glaucoma group (P < 0.05). There was a significant difference between the two groups for all stereometric parameters, except height variation contour, mean retinal nerve fibre layer thickness and retinal nerve fibre layer cross-sectional area stereometric parameters. There was also a significant difference between the groups for global, temporal, superior temporal and inferior temporal rim area parameters. In small discs, however, this difference disappeared in all parameters except temporal rim area and superior temporal rim area sectorial parameters. When all the cases were included, the quartet parameters having the highest specificity (80%) and sensitivity (74.3%) were cup volume, rim volume, cup shape measure and height variation contour parameters. Some HRTII parameters have better sensitivity and specificity than the others. It is necessary to pay special attention in evaluating small discs.