title: Can the SENSIMED Triggerfish®lens data be used as an accurate measure of intraocular pressure?
abstract: OBJECTIVE
  The SENSIMED Triggerfish®contact lens sensor (CLS) has an embedded micro-sensor that captures spontaneous circumferential changes at the corneoscleral junction and transmits them via an antenna to a device where these measurements are stored. During laparoscopic colorectal surgery, patients are placed in Trendelenburg position which has been shown to increase intraocular pressure (IOP). Laparoscopic colorectal surgery requires both pneumoperitoneum and Trendelenburg positioning; therefore, IOP can vary significantly. We aimed to assess whether circumferential changes in the corneoscleral area can be correlated to IOP changes measured using Tono-pen®XL applanation tonometer during laparoscopic colorectal surgery.
  
  
  METHODS
  Patients undergoing laparoscopic colorectal resections were included. On the day of surgery, baseline IOP was taken and the SENSIMED Triggerfish®CLS was then set up in one eye of the patient. During surgery (whilst under general anaesthetic), IOP measurements were taken in the contralateral eye using a Tono-pen®XL applanation tonometer every hour and any time the table was moved to record the fluctuations of IOP during surgery and any association with position change. The timings of these readings were documented.
  
  
  RESULTS
  Twenty patients were included in this study (six males, 14 females). Average age was 64.6 years (SD = 16.3). The fluctuation in IOP measured in the reference eye ranged between 6.3 and 46.7 mmHg. The mean correlation coefficient between CLS output measurements and these IOP measurements was r = 0.291 (95% CI).
  
  
  CONCLUSIONS
  Our results showed a weak correlation between the SENSIMED Triggerfish®CLS data output and IOP measurements taken using the Tono-pen®XL applanation tonometer.
authors.affiliation: Gastrointestinal Surgery, Nottingham Digestive Diseases Centre, National Institute for Health Research, Biomedical Research Unit, Queen's Medical Centre, Nottingham University Hospitals and University of Nottingham, Nottingham, UK.
authors.forename: Parveen
authors.identifier: http://orcid.org/0000-0002-7431-8834
authors.initials: P
authors.lastname: Vitish-Sharma
authors.affiliation: Gastrointestinal Surgery, Nottingham Digestive Diseases Centre, National Institute for Health Research, Biomedical Research Unit, Queen's Medical Centre, Nottingham University Hospitals and University of Nottingham, Nottingham, UK.
authors.forename: Austin G
authors.initials: AG
authors.lastname: Acheson
authors.affiliation: Ophthalmology Department, Queens Medical Centre, Nottingham University NHS Trust, Nottingham, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Stead
authors.affiliation: Ophthalmology Department, Queens Medical Centre, Nottingham University NHS Trust, Nottingham, UK.
authors.forename: John
authors.initials: J
authors.lastname: Sharp
authors.affiliation: Ophthalmology Department, Queens Medical Centre, Nottingham University NHS Trust, Nottingham, UK.
authors.forename: Ali
authors.identifier: http://orcid.org/0000-0003-2978-610X
authors.initials: A
authors.lastname: Abbas
authors.affiliation: Ophthalmology Department, Queens Medical Centre, Nottingham University NHS Trust, Nottingham, UK.
authors.forename: Marta
authors.initials: M
authors.lastname: Hovan
authors.affiliation: Gastrointestinal Surgery, Nottingham Digestive Diseases Centre, National Institute for Health Research, Biomedical Research Unit, Queen's Medical Centre, Nottingham University Hospitals and University of Nottingham, Nottingham, UK.
authors.forename: Charles
authors.initials: C
authors.lastname: Maxwell-Armstrong
authors.affiliation: Medical Statistics, Faculty of Medicine & Health Sciences, University of Nottingham, Nottingham, UK.
authors.forename: Boliang
authors.initials: B
authors.lastname: Guo
authors.affiliation: Ophthalmology Department, Queens Medical Centre, Nottingham University NHS Trust, Nottingham, UK.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: King
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003107:Colorectal Surgery; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D010535:Laparoscopy; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D056888:Patient Positioning; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000592:standards*
keywords: 
  IOP
  ; SENSIMED; Trendelenburg; laparoscopic