title: [How much pressure is applied on the eye balls during craniotomy?: Measurement with FlexiForce contact surface force sensor].
abstract: BACKGROUND
  Visual loss following craniotomy is a serious postoperative complication in which elevation of ocular pressure during retraction of the skin flap may cause retinal ischemia. We reported that continuous monitoring of extraocular pressure with the FlexiForce sensor may avoid excessive skin flap retraction during craniotomy and thus prevent ocular complications.
  
  
  METHODS
  Between January 2008 and December 2011, we analyzed data from 46 consecutive patients for whom continuous monitoring of extraocular pressure with FlexiForce sensor was performed. This sensor continuously displays the compressive force, allowing surgeons to check values on the monitor at any time. An alarm sounds if 50 gf is exceeded. We analyzed the temporal course of extraocular pressure and the relationship with patient characteristics.
  
  
  RESULTS
  No visual complications were encountered in this patient series. Maximum compressive force during craniotomy was 35.8±27.2 gf, with increases typically seen when surgeons used hooks or drills. However, due to the alarm, no prolonged periods of high force were noted in any patient. Effective methods for reducing force were: (1) taking off hooks on the compressive side; (2) changing the direction of hook tension; and (3) placing cushions such as gauze under the side of the skin flap. Maximum compressive force during microsurgery was 21.8±18.4 gf, and correlated with the beginning force of microsurgery.
  
  
  CONCLUSIONS
  Compressive force was greatly reduced compared to the force reported previously. The etiologies of visual disability are not fully understood, but this sensor may be helpful in reducing extraocular compression.
authors.affiliation: Department of Surgical Neurology, Research Institute for Brain and Blood Vessels, Akita, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Okada
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nishimura
authors.forename: Akifumi
authors.initials: A
authors.lastname: Suzuki
mesh_terms: D000328:Adult; D000368:Aged; D003399:Craniotomy / Q000379:methods*; D005123:Eye / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008866:Microsurgery / Q000379:methods*; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011183:Postoperative Complications / Q000517:prevention & control; D011312:Pressure / Q000009:adverse effects