To compare the accuracy of the optic nerve sheath diameter (ONSD) measured by ocular ultrasonography (US) versus magnetic resonance imaging (MRI) for the diagnosis of increased intracranial pressure (ICP).A systematic search of studies evaluating US ONSD or MRI ONSD for the diagnosis of increased ICP was performed. Data were extracted independently by two authors. We used the bivariate random-effects model to evaluate the diagnostic feasibility of measuring the ONSD in patients increased ICP. A summary receiver operating characteristic (SROC) graph was adopted to calculate sensitivity and specificity. Subgroup analysis was used to explore potential difference in US ONSD and MRI ONSD.A total of 31 studies were included, in which there were 1783 patients diagnosed with US ONSD and 730 patients diagnosed with MRI ONSD. Twenty studies reporting US ONSD were included for quantitative synthesis. The US ONSD had a high diagnostic accuracy, involving estimated sensitivity of 0.92 (95%CI 0.87-0.95), estimated specificity of 0.85 (95%CI 0.79-0.89), positive likelihood ratio (PLR) of 6.0 (95%CI 4.3-8.4), negative likelihood ratio (NLR) of 0.10 (95%CI 0.06-0.15) and Diagnostic Odds Ratio (DOR) of 62 (95%CI 33-117). The data of 11 studies adopting MRI ONSD was pooled. The MRI ONSD demonstrated estimated sensitivity of 0.70 (95%CI 0.60-0.78), estimated specificity of 0.85 (95%CI 0.80-0.90), PLR of 4.8 (95%CI 3.4-6.7), NLR of 0.35 (95%CI 0.27-0.47) and DOR of 13 (95%CI 8-22). The subgroup analysis showed that US ONSD demonstrated a higher sensitivity (0.92 versus 0.70; p<0.01) and almost equal specificity (0.85 vs. 0.85; p=0.67) compared with MRI ONSD.Measurement of ONSD can be a useful tool to predict raised ICP. The US ONSD demonstrated better accuracy than MRI ONSD for the diagnosis of increased ICP.