ABSTRACT
Background Heidelberg Retinal Tomograph (HRT) has been widely used in clinical diagnosis of glaucomatous optic neuropathy,importantly,the measurement results of HRT may be affected by myopia.Therefore,studying the effect of different refractive status and axial length on structural parameters of the optic disc is important.Objective This study was to evaluate the influence of refractive error and axial length to optic nerve head parameter measured by HRT.Methods The parents who participate in Guangzhou Twin Study were enrolled in this investigation from July 2006 to August 2011.The regular eye examinations,including visual acuity,slit lamp,fundus,auto-refraction,HRT-Ⅲ and intraocular lens (IOL) Master,were performed on all the subjects.Thc data from right eyes of subjects were collected and analyzed.The linear correlation analysis and multiple linear regression analysis were applied to analyze the correlation between HRT optic papilla configuration parameter and equivalent sphere and ocular axis length.Results A pilot prospective series cases observational study was designed.1748subjects were enrolled in this study.The disc area (DA) (P=0.021),rim area (RA) (P＜0.001),rim volume (RV) (P＜0.001),mean retinal nerve fiber layer thickness (mRNFLt) (P＜0.001) and retinal nerve fiber layer cross section area (RNFLcsa) in the high myopia were greater than those of the emmetropic group,with significant difference between the two groups (P＜0.001).However,the cup area (CA),cup/disk area ratio (C/DAR) and cup volume (CV) were less in the high myopic group than those of the emmetropic group (P=0.004,P＜0.001 and P＜O.001),respectively.In the mild-moderatc myopic group,the RV,mRNFLt and RNFLcsa were greater than those of the emmetropic group (all of the P value less than 0.001),but the numbers of DA,CA,C/DAR,and CV were less than those of the emmetropic group,the differences were significant and their P valuables were 0.038,＜ 0.001,＜0.001 and 0.001 respectively.The differences of structure parameters between the hyperopia group and the emmetropic group were not statistically significant (P＞0.05).The DA,CA,RA,C/DAR,CV,RV,mean cup depth (MCD),maximum cup depth (MxCD),cup shape measure (CSM),mRNFLt and RNTLcsa were (2.04±0.43) mm2,(0.49±0.34) mm2,(1.55 ± 0.34) mm2,0.23-0.13,(0.11 ± 0.12) mm3,(0.45 ± 0.19) mm3,(0.21 ± 0.09) mm,(0.60±0.21) mm,-0.21 ± 0.07,(0.29 ± 0.07) mm and (1.46 ± 0.36)mm2,respectively,in the 1748 eyes of 1748 subjects.No significant correlation was found between the DA value with SE (r=-0.032,P =0.186).However,weaker positive correlations were seen between the CA,C/DAR,CV,MCD,MxCD with SE (r=0.139,0.163,0.130,0.004,0.054,P＜ 0.05) and negative correlation between RA,RV,mRNFLt and RNFLcsa with SE (r =-0.178,-0.331,0.241,-0.239,P＜0.001).With the increase of the ocular axial length,the DA,RA,RV,mRNFLt and RNFLcsa values were enlarged,and the CV value was smaller.With the increase of CA,the RA,C/DAR,CV,RV,MCD,MxCD,CSM and RNFLcsa values elevated,but mRNFLt value was decreased.Conclusions Refractive error is not associated with DA,but the measuring results are different among various refractive groups.Refractive error,ocular axial length and DA affect the measuring result of HRT.
ABSTRACT
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.