THE CUMULATIVE NORMALIZED RIM DISC AREA RATIO CURVE

Background: The assessment of the cup of the optic disc depends, among other criteria, on the disc area. A small cup in a small optic disc c an indicate an advanced glaucomatous lesion, while on the other hand a large cup in a large optic disc can be normal. Therefore, a cumulativ e normalised rim/disc area ratio curve could help to distinguish betwe en glaucomatous and normal optic cups. The aim of our study was to cal culate and to evaluate such a cumulative normalised rim/disc area rati o curve. Methods: Heidelberg Retina Tomograph examinations of the opti c nerve head of 100 randomly selected eyes of 100 normal subjects were evaluated. We calculated the disc area-adjusted normalised rim/disc a rea ratio in sectors of 10 degrees. The 95th, 90th and 50th percentile s of each of the 36 sectors were displayed in descending order. Result s: In relation to the normal percentile curves, it is possible to disp lay an individual normalised rim/disc area ratio curve. We obtained su ch curves for a normal optic disc, optic nerve heads with moderate and advanced lesions and a small optic disc with glaucomatous damage. Con clusion: We present a new display mode for the results of Heidelberg R etina Tomograph optic nerve head examination, which may be helpful for easy and reliable assessment of the local, diffuse and combined compo nents of glaucomatous optic nerve head damage depending on optic disc size.