title: Transorbital sonographic measurement of normal optic sheath nerve diameter in nigerian adult population.
abstract: BACKGROUND
  The optic nerve covering is elastic enough to allow a detectable enlargement in response to changes in intracranial pressure. The objective of the present study was to determine the optic nerve sheath diameter (ONSD) in normal Nigerian adults.
  
  
  METHODS
  This study was conducted on 400 healthy adults. The ONSD was measured at 3 mm posterior to the globe using a 7.5 MHz linear transducer.
  
  
  RESULTS
  The study population consisted of 192 males and 208 females with mean age of 36.94 years (SD 16.63). The range of values for ONSD was 3.36 to 5.1 mm. The median right ONSD was 4.110 with a range of 3.36-4.86 mm (mean: 4.18 mm (SD 0.49)), while the median left ONSD was 4.35 mm with a range of 3.77-5.10 mm (mean: 4.17 + mm (SD 0.44)). No statistically significant variation in ONSD was found between the right and left sides (P = 0.12) and also between male and female participants (P = 0.296 and 0.745 for the respective right and left ONSD).
  
  
  CONCLUSIONS
  The normal reference values of ONSD measurements in adults were obtained. It showed no significant correlation with side (right and left), age, and sex. Furthermore, there is no significant correlation of ONSD with the body height and weight.
authors.affiliation: Department of Radiology, Bayero University/Aminu Kano Teaching Hospital, PMB 3011, Kano, Nigeria.
authors.forename: Ismail
authors.initials: I
authors.lastname: Anas
keywords: diameter; intracranial pressure; optic nerve; sonography