A cross sectional study among established primary open angle glaucoma patients was conducted to study the correlation of global indices measured by automated perimetry and retinal nerve fibre layer(RNFL) thickness by optical coherence tomography(OCT). We noticed a statistically significant correlation (p<0.00001) between average RNFL thickness and mean deviation in both the eyes. Negative correlation was obtained between average RNFL thickness and pattern standard deviation but showed statistical significance (P<0.00001). The correlation between vertical cup–disc ratio and cup area volume in mm2 by OCT did not show any statistical significance to global indices. In established glaucomatous patients with visual field loss, a significant correlation exists between the global perimetric indices and the Total average RNFL thickness. The instruments like OCT are valuable tools to provide objective measurements of RNFL thickness and to give quantitative reproducible results; also interpretation of the structural tests is complementary to the subjective visual