Introduction: This study is to determine whether a bedside ultrasonographic measurement of optic nerve sheath diameter can accurately predict the computed tomographic (CT) findings of elevated intracranial pressure in adult head injury patients in the emergency department (ED).Methodology: A prospective, analytical study on adult ED patients with suspected intracranial injury. Using a 7.5-10MHz ultrasonographic probe on the closed eyelids, both horizontal and vertical optic nerve sheath diameter was measured 3 mm behind the globe in each eye. A mean binocular optic nerve sheath diameter greater than 5.00 mm was considered abnormal. Cranial CT findings of shift, edema, or effacement suggestive of elevated intracranial pressure were used to evaluate optic nerve sheath diameter accuracy. Results: 255 patients were enrolled in the study. The average age was 40.5 years, and median GCS score was 13 (range 3 to 15). Optic nerve ultrasound had high sensitivity of 100%, negative predictive value was 100% specificity of 86.9%, with a positive predictive value of 88.0% for detecting elevated intracranial pressure compared with CT when cut-off ONSD was taken as 5.0mm.A receiver operating characteristic (ROC) curve for elevated ICP was drawn to establish the optimal cut-off value of ONSD which demonstrated an area under the curve of 0.982. Cut-off value of >5.2 mm yielded the best test characteristics and accurately predicted raised ICP with a sensitivity of 100%, specificity of 90.8%, positive predictive value of 91.2% and the negative predictive value of 100%.Conclusion: Prediction of increased intracranial pressure by bedside ED optic nerve sheath diameter ultrasonography is comparable with CT brain and carries a significant correlation in terms of accuracy, sensitivity, specificity and positive predictive value.