title: Coronal Axis Measurement of the Optic Nerve Sheath Diameter Using a Linear Transducer.
abstract: OBJECTIVE
  The true optic nerve sheath diameter cutoff value for detecting elevated intracranial pressure is variable. The variability may stem from the technique used to acquire sonographic measurements of the optic nerve sheath diameter as well as sonographic artifacts inherent to the technique. The purpose of this study was to compare the traditional visual axis technique to an infraorbital coronal axis technique for assessing the optic nerve sheath diameter using a high-frequency linear array transducer.
  
  
  METHODS
  We conducted a cross-sectional study at an academic medical center. Timed optic nerve sheath diameter measurements were obtained on both eyes of healthy adult volunteers with a 10-5-MHz broadband linear array transducer using both traditional visual axis and coronal axis techniques. Optic nerve sheath diameter measurements were obtained by 2 sonologists who graded the difficulty of each technique and were blinded to each other's measurements for each participant.
  
  
  RESULTS
  A total of 42 volunteers were enrolled, yielding 84 optic nerve sheath diameter measurements. There were no significant differences in the measurements between the techniques on either eye (P = .23 [right]; P = .99 [left]). Additionally, there was no difference in the degree of difficulty obtaining the measurements between the techniques (P = .16). There was a statistically significant difference in the time required to obtain the measurements between the traditional and coronal techniques (P < .05).
  
  
  CONCLUSIONS
  Infraorbital coronal axis measurements are similar to measurements obtained in the traditional visual axis. The infraorbital coronal axis technique is slightly faster to perform and is not technically challenging.
authors.affiliation: Department of Emergency Medicine, University of Arizona Medical Center, Tucson, Arizona USA (R.A., L.A.S., S.A.); and Department of Pharmacy, College of Medicine, University of Arizona, Tucson, Arizona USA (A.E.P.). richardamini@gmail.com.
authors.forename: Richard
authors.initials: R
authors.lastname: Amini
authors.affiliation: Department of Emergency Medicine, University of Arizona Medical Center, Tucson, Arizona USA (R.A., L.A.S., S.A.); and Department of Pharmacy, College of Medicine, University of Arizona, Tucson, Arizona USA (A.E.P.).
authors.forename: Lori A
authors.initials: LA
authors.lastname: Stolz
authors.affiliation: Department of Emergency Medicine, University of Arizona Medical Center, Tucson, Arizona USA (R.A., L.A.S., S.A.); and Department of Pharmacy, College of Medicine, University of Arizona, Tucson, Arizona USA (A.E.P.).
authors.forename: Asad E
authors.initials: AE
authors.lastname: Patanwala
authors.affiliation: Department of Emergency Medicine, University of Arizona Medical Center, Tucson, Arizona USA (R.A., L.A.S., S.A.); and Department of Pharmacy, College of Medicine, University of Arizona, Tucson, Arizona USA (A.E.P.).
authors.forename: Srikar
authors.initials: S
authors.lastname: Adhikari
mesh_terms: D000328:Adult; D000465:Algorithms; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D015588:Observer Variation; D009900:Optic Nerve / Q000000981:diagnostic imaging*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*
keywords: emergency ultrasound; measurement; ocular ultrasound; optic nerve; optic nerve sheath diameter; point-of-care ultrasound