OBJECTIVE To establish whether the structural parameters provided by GDx can be used to reflect functional damage in the mean defect of visual field. METHODS 97 (191 eyes) patients with primary open angle glaucoma underwent examination with GDx and Octopus 1-2-3 automatic perimeter. The relationship between the retinal nerve fiber layer parameters and mean defect of visual field was analysed by ANOVA, Pearson's correlation(r), scatter plot and linear regression. RESULTS The parameters of GDx decreased with increasing mean defect of visual field, measured both globally and regionally; r: SA = -0.58, TSNIT = -0.52, IA = -0.52, NFI = -0.48 and IES = -0.33. All parameters were negative correlation with mean defect of visual field and there was significant correlation among these parameters, except IES (P < 0.05). The superior mean defect of visual field increased with decreasing inferior RNFL (r = -0.61), inferior visual field mean defect increased with decreasing superior RNFL (r = -0.59). There were significant correlation among these parameters. CONCLUSIONS Quantitative measures of the retinal nerve fiber layer using GDx were correlated with mean defect of visual field in patients with glaucoma. GDx can be used for follow up.