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Continuous Intraocular Pressure Monitoring by Means of the Sensimed Triggerfish® System

European Ophthalmic Review, 2011,5(1):43-5 DOI: http://doi.org/10.17925/EOR.2011.05.01.43

Abstract:

Intraocular pressure (IOP), like other biological parameters, has a 24-hour rhythm with physiological oscillations around 5mmHg. Recently, it has been demonstrated that IOP fluctuations represent an independent parameter for progression of glaucoma. The most common clinical methods able to detect the diurnal state of IOP are the tonometric curve (with IOP measurements taken from 9:00 am to 20:00 pm) or two provocative tests, such as the water drinking test (WDT) and the ibopamine test. Recently introduced in clinical practice, the Sensimed Triggerfish® is a system enabling continuous IOP monitoring based on a disposable contact lens with a sensor linked to a telemetric microprocessor. The purpose of this project was to investigate the clinical applicability of the system as an additional tool, providing useful information for the management of glaucoma patients. Of eight evaluated patients, two cases are presented in detail in this report. The monitoring system that provides 24-hour continuous data appears to be very promising, as it captures clinically useful, real-life IOP fluctuations day and night while patients maintain normal activities, including undisturbed sleep.

Support: The publication of this article was funded by Sensimed AG.
Keywords: Glaucoma, continuous intraocular pressure (IOP) monitoring, water drinking test, IOP fluctuation, 24-hour IOP
Disclosure: Jeanette Lindell is an employee of Sensimed AG. The other authors have no conflicts of interest to declare.
Received: April 01, 2011 Accepted: April 20, 2011
Correspondence: Vetrugno Michele, Department of Ophthalmology and Otolaryngology, University of Bari, Policlinico Universitario, piazza Giulio Cesare 11, 70124 Bari, Italy. E: michelevetrugno@libero.it

Glaucoma is a progressive, chronic and irreversible neuropathy with typical structural changes at the optic nerve head and with functional defects in the visual field, leading to blindness at the end stage. It is estimated that over 60 million people worldwide are now affected by this disease and this number will dramatically increase to about 80 million by 2020. Glaucoma is the second leading cause of blindness in the world: it is estimated that 10% of people affected by glaucoma progress to blindness.1
Glaucoma is a multifactorial disease, but the only proven way to reduce its progression is by lowering intraocular pressure (IOP), by means of pharmacological, laser or surgical therapy.
Intraocular Pressure Management
IOP is a biological parameter that has a 24-hour biorhythm: in the majority of people it shows little variation – without clinically significant differences during the 24-hour period – while in some cases, IOP may be higher during the morning, or in the afternoon, or during the night.2 IOP oscillations of up to 5mmHg are observed in healthy subjects, while they may reach up to 11mmHg in glaucoma patients. IOP fluctuations have been recognised as a significant risk factor for the development and progression of glaucoma.3 Therefore, a single IOP measurement taken during office hours, may not provide information regarding the effective IOP behaviour during the entire 24-hour period. In clinical practice, glaucoma patients frequently present with progressive visual field loss despite IOP values in the range of normality at follow-up visits. In these cases, a tonometric daily curve (IOP measurements taken every four hours from 9:00 am to 20:00 pm) may point out IOP peaks during the day. In other cases, a water drinking test (WDT) or an ibopamine test can be performed with the same purpose. Glaucoma patients with controlled IOP after surgery still show significant increase of IOP when subjected to the WDT.4 Both the ibopamine test and WDT were shown to correlate with daytime peak IOP.5,6 A relationship between WDT and 24-hour peak IOP has been suggested.7 Finally a 24-hour tonometric curve with IOP measurements taken also during the night may be established. Twenty-four-hour IOP curves are more frequently performed in a clinical trial setting than as standard clinical practice, as it requires patient hospitalisation.8,9
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Keywords: Glaucoma, continuous intraocular pressure (IOP) monitoring, water drinking test, IOP fluctuation, 24-hour IOP