Purpose: The aim of the study was to compare optic nerve head (ONH) and Retinal nerve fibre layer (RNFL) thickness tomographic parameters measured by Spectral Domain (SD) OCT and to identify which measurements are best able to differentiate between normal and glaucomatous eyes in Indian population. Design: Cross sectional prospective diagnostic study. Methods: Participants were recruited from a universitybased clinic. 30 age matched normal and 30 Open angle glaucomatous eyes who full filled the inclusion criteria were selected. All cases were subjected for optic nerve head (ONH) and Retinal nerve fibre layer (RNFL) thickness evaluation with the SD OCT (Carl Zeiss). All parameters were compared with normal eyes. The areas under the receiver operating curves AROC were calculated for each single parameter and then compared. Results: Comparative analysis of SDOCT parameters revealed statistically significant difference in all five RNFL parameters between both the groups. Most of the ONH parameters demonstrated statistically significant difference in glaucoma group when compared with control group. The inferior quadrant (0.976) and average RNFL thickness (0.970) obtained the highest AROC values in open angle glaucoma group. The rim area had the best diagnostic accuracy among the ONH parameters (AROC = 0.951). Conclusion: In the present study, RNFL parameters presented with better discriminatory abilities than ONH parameters in the normal and glaucomatous group. Out of all the RNFL and ONH parameters inferior quadrant RNFL thickness, average RNFL thickness and rim area had the best ability to discriminate between glaucomatous and normal eyes.

Keywords: Optical Coherence Tomography; Retinal Nerve Fiber Layer Thickness; Optic Nerve Head Analysis; Spectral Domain