<strong>BACKGROUND</strong> Epiduroscopy is commonly used for the evaluation and treatment of low back pain. Saline with or without local anesthetic addition was used to visualize epidural space structure during this procedure. A rapid increase in epidural space pressure is transmitted into the spinal space to the optic nerve sheath. This study aimed to estimate the effects of epiduroscopy on optic nerve sheath diameter (ONSD) according to the volume of fluid using the ultrasonographic measurement of optic nerve diameter in adult patients. <strong>MATERIAL AND METHODS</strong> Sixty patients who had been treated for low back pain with epiduroscopy using low-volume (LV) or high-volume (HV) fluid application were enrolled into the study. Measurement of ONSD was performed before (T0) and immediately after epiduroscopy (T1), at 10 min (T2), and 20 min (T3) after the epiduroscopy. <strong>RESULTS</strong> Both groups showed significant differences over time in ONSD (PGroup×Time=0.001). The HV group showed greater changes from T0 to T2 and T3 than the LV group in ONSD. However, in both groups, ONSDs at T2 and T3 were significantly larger than those with the highest values at T2 compared to T0. <strong>CONCLUSIONS</strong> Ultrasonography of ONSD presents a good level of diagnostic accuracy for identifying epidural hypertension. In the clinical decision-making phase, this may help physicians to be more cautious about volume when performing epidural injections to treat this disease.