Abstract: An apparatus containing four linear gauges (I, II, III and IV) allows simultaneous measurement of the main parameters of a lens blank, namely the vertex radius (or asphericity), the centre thickness, and the front surface sag. A first head member (6) presents contacts (12) which contact the front conicoid surface of a lens blank (101) on a first circle. A measuring head (8) presents contacts (13) on a second circle. Gauges (I and II) measure relative displacements between the contacts (12 and 13) and the end of pointer (3), from which the asphericity or vertex radius can be calculated. Gauges (III and IV) are coupled respectively to the rear and front surfaces of the lens blank (101). The perimeter (106) of the lens blank (101) is aligned with a reference plane (R). The displacements of the gauges (III and IV) can be used to calculate the centre thickness and front surface sag of the lens.