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Br J Ophthalmol. 2017 Oct;101(10):1323-1328. doi: 10.1136/bjophthalmol-2016-308710. Epub 2017 Mar 7.

Twenty-four hour intraocular pressure monitoring with the SENSIMED Triggerfish contact lens: effect of body posture during sleep.

Author information

Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, Toronto, Ontario, Canada.
Institut Català de la Retina, Barcelona, Spain.
Sleep Research Unit, Toronto Western Hospital, Toronto, Ontario, Canada.
School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada.



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.


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


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.


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').


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.




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

[Indexed for MEDLINE]

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