The arrangement in a tonometer has a probe that is brought into contact with the surface of the eye and the intraocular pressure in the eye is derived from the variations in the velocity of the probe. The probe is formed of a piece of a non-magnetic substance. The arrangement includes a holder located in the tubular component and attached to a shaft providing the force for the measurement, in which holder there is a guiding means for guiding a movement of the probe along an internal surface of the tubular component.