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Free Content A new induction-based impact method for measuring intraocular pressure

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An improved induction-based impact method for measuring intraocular pressure is presented.


A light probe containing a permanent magnet is launched towards the eye using a solenoid. The probe hits the eye and bounces back. The same solenoid, inside which the probe moves, is used to detect the movement and impact of the probe, because the moving magnet induces voltage in the solenoid. In the clinical study, the Goldmann applanation tonometer was used as a standard. Handheld and fixed tonometers were also compared by means of measurements in pressurized pig eyes.


At a low intraocular pressure (IOP), there is a longer impact time than at a high IOP. A handheld tonometer causes more variation in impact times, especially at low intraocular pressure (IOP), than a fixed tonometer.


The new induction-based impact method can be used to measure IOP. When a fixed tonometer is used, there is less variation in impact times.

Keywords: impact; induction; intraocular pressure; measurement; tonometer

Document Type: Original Article

Affiliations: Department of Ophthalmology, Helsinki University Central Hospital, Helsinki, Finland

Publication date: April 1, 2000

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