Background Normal adult optic disc rim width follows inferior ≥ superior ≥ nasal ≥ temporal (ISNT) rule.Analysis of the optic disc structural parameters with Heidelberg retina tomograph (HRT) can understand whether ISNT principle is suitable to other optic disc structure parameters.Objective This study was to investigate the characteristics of optic nerve head structure parameters in normal Chinese adults.Methods The parents of twins who participated Guangzhou Twin Eye Study were enrolled in Zhongshan Ophthalmic Center from 2006 June to 2011 August.All subjects received the routine eye examinations,including visual acuity,slit lamp microscope,direct ophthalmoscope examination,auto-refraction examination and HRT Ⅲ examination.All data from the right eyes were collected and analyzed.HRT values from different quadrants of optical nerve head were compared with one-way analysis of variance,and the multiple comparison between quadrants was carried out by Bonferroni test.The differences of optical nerve head parameters in different gender were analyzed using independent sample t test and Bland-Altman test.Results In this study,1672 eyes of 1672 subjects were included,with the 759 male and 913 female persons and average age of (41.8±5.3)years.No significant differences were seen in the disc area (DA)between the superior and inferior,as well as the nasal and temporal quadrants among the subjects (P＞0.05).In addition,there were not significantly different in the rim area (RA) between the superior and nasal disc as well as the rim volume (RV) among the inferior,superior and nasal disc (P＞O.05).However,significant differences were found in the cup area (CA),cup/disk area ratio (C/DAR),cup volume (CV),mean cupdepth (MCD),maximum cup depth (MxCD),height variation contour (HVC),cup shape measure (CSM),mean retinal nerve fiber layer thickness (mRNFLT) and retinal nerve fiber layer cross section area (RNFLcsa) among the different quadrants (P＜0.001).The local differences from only DA and RA complied with an ordination of the ISNT rule.The values of DA,CA,C/DAR,CV,MCD,MxCD from male individuals were higher,but those of the RV,HVC,mRNFLT RNFLcsa were lower in comparison with female individuals.Nevertheless,all the differences were ＜ 0.1 with a maximal mean difference in DA and CA (both 0.07 mm2).Conclusions The optical nerve head configurations measured by HRT have different distributing characteristics in four quadrants in normal adults.Most parameters show the higher values in the inferior and superior than those in nasal and temporal of disc,but DA and RA meet ISNT rule.The differences of most parameters between male and female subjects can be ignored.