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Twenty-four hour intraocular pressure monitoring with the SENSIMED Triggerfish contact lens: effect of body posture during sleep
  1. Laura Beltran-Agulló1,2,
  2. Yvonne M Buys1,
  3. Farzana Jahan3,
  4. Colin M Shapiro1,
  5. John G Flanagan1,4,
  6. Jason Cheng1,
  7. Graham E Trope1
  1. 1Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, Toronto, Ontario, Canada
  2. 2Institut Català de la Retina, Barcelona, Spain
  3. 3Sleep Research Unit, Toronto Western Hospital, Toronto, Ontario, Canada
  4. 4School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada
  1. Correspondence to Dr Laura Beltran-Agulló, Glaucoma Department, Institut Català de la Retina, C/Ganduxer 177, Barcelona 08022, Spain; laurabeltragullo{at}


Purpose To determine the difference in relative intraocular pressure (IOP) measured by the SENSIMED Triggerfish (TF) contact lens in flat compared with 30° head-up sleeping positions in patients with progressive primary open-angle glaucoma or normotensive glaucoma, based on recent or recurrent disc haemorrhage.

Design Prospective, randomised, cross-over, open-label comparative study.

Methods IOP was monitored for 24 hours using TF on two separate sessions. Patients were randomly assigned to sleep flat one night and 30° head-up the other. Outputs in arbitrary units were obtained. Sleep and wake periods were defined as 22:00–6:00 and 8:00–22:00, respectively. Mean TF values during sleep and wake periods and wake–sleep and sleep–wake slopes were calculated for each session. TF output signals were compared between positions.

Results Twelve subjects completed the study. Significant mean positive slopes were noted during the sleep period for both positions (p<0.01). No significant differences in the TF mean values were observed between positions (p=0.51). Six (54%) subjects had mean TF values significantly higher during the flat supine session, while four (36%) subjects had higher values during the head-up session. A significant increase in Goldmann IOP (p=0.001) and TF (p=0.02) measurements were observed after 24 hours of TF wear (‘drift phenomenon’).

Conclusions Sleep position affects IOP as measured by TF in some patients with progressive glaucoma. The upward drift in TF output detected in >50% of the subjects requires further investigation to establish whether the increased output values over time are an artefact induced by the TF or a real change in IOP.

Trial registration number NCT01351779

  • Glaucoma
  • Optic Nerve
  • Diagnostic tests/Investigation
  • Contact lens

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  • Contributors GET and YMB: conception and design of the study, interpretation of the results, revision and drafting the work; FJ: data acquisition (sleep laboratory) and revision of work; CMS: design of the study and revision of work (sleep laboratory); JC: recruitment, data interpretation and revision of work; JGF: design of the study, interpretation of the results and revision of the work; LB-A: recruitment, data acquisition, interpretation of the results and drafting the work.

  • Funding FJ and GET: SENSIMED provided equipment supplies and funding for patient compensation. Funding was also provided by the Canadian Glaucoma Clinical Research Council.

  • Competing interests None declared.

  • Patient consent Obtained.

  • Ethics approval Research Ethics Board of the University Health Network at the University of Toronto.

  • Provenance and peer review Not commissioned; externally peer reviewed.