RESUMO
INTRODUCTION: Clinical determination of the outer limits of the optic disk (OD) doesn't always correspond to the true anatomic limits of the optic nerve head (ONH) defined by the Bruch's membrane opening (BMO). A new index analyzing the OD with optical coherence tomography (OCT), "minimal rim width" (BMO-MRW), evaluates the smallest thickness of the neuroretinal rim between the BMO and the internal limiting membrane. The purpose of this study was to evaluate new software for automatic measurement of the BMO-MRW. MATERIALS AND METHODS: This study investigated 95 eyes: 40 control eyes and 55 eyes followed and treated for primary open angle glaucoma (42 early glaucoma, 7 moderate glaucoma and 6 advanced glaucoma). After a precise localization of the OD center, 24 radial scans of the ONH are taken with the Spectralis OCT (Heidelberg Engineering, Germany). From the 48 measurements of BMO-MRW, the mean thickness as well as that in each of the 6 papillary sectors of this new index are calculated. ROC curves analysis (receiver operating characteristic) was used to assess the diagnostic capabilities of the various parameters. RESULTS: Thicknesses of all parameters were statistically lower in glaucoma than in controls. The mean value and inferotemporal sector (IT) had the best diagnostic capabilities without significant difference between them (BMO-MRW-average = 0.890 ± 0.062, BMO-MRW-IT = 0.881 ± 0.066, P = 0.59). The area under the curve was lowest in the temporal sector (0.820 ± 086 statistically lower than the average value, P = 0.04). CONCLUSIONS: This preliminary study of a new automated analysis of the neuroretinal rim highlights the diagnostic value of the BMO-MRW index. This evaluation appears to be best correlated with the anatomy of the ONH with good diagnostic sensitivity.