Abstract: This invention relates to an applanation tonometer for measuring a patient's intraocular pressure by applying an applanating pressure to the cornea of the patient's eye to produce a flattened area of predetermined size thereon, such applanating pressure being determined conjointly by an adjustable main spring and at least one compensating spring, the characteristics of the compensating spring being such that the total applanating pressure will bear an approximately linear relationship to an indicating movement dependent on the adjustment of the main spring. Preferably, the adjustment of the main spring is effected by control means operative to adjust the anchorage of such spring, the control means also acting to effect movement of an indicating member for indicating the said applanating pressure.