title: Quantitative relations between the eyeball, the optic nerve, and the optic canal important for intracranial pressure monitoring.
abstract: OBJECTIVE
  To find correlations between diameters of the optic nerve sheath (ONSD), the eyeball, and the optic canal that might be important for intracranial pressure monitoring.
  
  
  METHODS
  In a prospective cohort study, the CT data of consecutive 400 adults (18+) with healthy eyes and optic nerves and absence of neurological diseases were collected and analyzed. When the CT scans were obtained, the diameters of the optic nerve sheath, the eyeball, and the optic canal were measured and statistically analyzed. The data obtained from the left and from the right eyeballs and optic nerves were compared. The correlation analysis was performed within these variables, with the gender, and the age.
  
  
  RESULTS
  In healthy persons, the ONSD varies from 3.65 mm to 5.17 mm in different locations within the intraorbital space with no significant difference between sexes and age groups. There is a strong correlation between the eyeball transverse diameter (ETD) and ONSD that can be presented as ONSD/ETD index. In healthy subjects, the ONSD/ETD index equals 0.19.
  
  
  CONCLUSIONS
  The calculation of an index when ONSD is divided by the ETD of the eyeball presents precise normative database for ONSD intracranial pressure measurement technique. When the ONSD is measured for intracranial pressure monitoring, the most stable results can be obtained if the diameter is measured 10 mm from the globe. These data might serve as a normative database at emergency departments and in general neurological practice.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Assaf Harofe Medical Center, Affiliated to Sackler Faculty of Medicine, Tel Aviv University, Zerifin, Israel. vaimed@yahoo.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Vaiman
authors.forename: Paul
authors.initials: P
authors.lastname: Gottlieb
authors.forename: Inessa
authors.initials: I
authors.lastname: Bekerman
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D009915:Orbit / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D012016:Reference Values; D014057:Tomography, X-Ray Computed; D055815:Young Adult