The impact of refractive errors and axial length on the structural parameters of the optic disc / 中华实验眼科杂志

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.