effect of scuba-diving on optic nerve and sheath diameters

background :there is not any data available about the effect of high bar pressure condition on intracranial pressure. in this study, the effect of diving on the optic nerve and sheath diameters as non-invasive markers of intracranial pressure has been investigated.   methods : twenty professional male divers from twenty one volunteers were chosen for this cross-sectional study. only one person who had a history of barotraumas was excluded. each diver then completed a questionnaire on demographic data, medical and diving history. nineteen other volunteers were selected to represent a control group. a 10-mhz linear ultrasonic probe was used to measure the optic nerve sheath diameters of both eyes in closed and supine position and its relationship with diving history of divers was determined.   results : it was found that divers have a higher mean optic nerve sheath diameter compared to the normal population as previously reported by other studies. the mean diameter of the left and right optic nerve sheaths were 6.4±0.7, 6.5±0.9 mm respectively and a significant relationship between optic nerve sheath diameter and diving history was found.   conclusion : results showed that divers have a higher optic nerve diameter than the general population. however, our result cannot yet be considered as a marker of intracranial pressure in divers as it was conducted on an limited number of subjects and so a bigger study should be undertaken for this purpose.