Background: Intracranial hypertension is a common life and vision threatening condition, intracranial pressure (ICP) can only be measured by invasive procedures. Distension of optic nerve sheath in association with raised ICP has been proven by the clinical trials. Transorbital sonographic measurement of optic nerve sheath diameter (ONSD) can be a simple noninvasive method for detection of raised ICP, however until now there is no consensus on upper normal limit of ONSD. The aim of the study is to measure optic nerve sheath diameter (ONSD) in healthy adults to provide normative data in a sample of Iraqi population.
Method and patient: an observational cross-sectional study was conducted in Ibn Alhaitham eye teaching hospital, Baghdad, Iraq. Both eyes of 98 healthy adult volunteers aged 19 to 77 were examined using Absulu ultrasound machine with 20 MHz annular probe. Two measurements of ONSD were taken 3mm behind the eye globe and the average was calculated.
Result: Optic nerve sheath diameter measurements ranged from 3.78mm to 7. 13mm.The mean was 5.54mm with standard deviation of 0.59mm and a median of 5.56mm. The 95% percentile was 6.53mm. There was no statistically significant relationship between ONSD measurement and gender or age.
Conclusions: The mean ONSD measured by transorbital ultrasound was 5.54mm and the upper normal limit was 6.5mm (95% percentile) in a sample of Iraqi population.