This International Standard, together with ISO 15004-1, specifies requirements and test methods for continuously or digitally indicating ophthalmometers. Certain types of ophthalmometer have sufficient resolution and range (see Table 2) to adequately measure the radii of curvature of contact lenses complying with ISO 18369-3:2006, 4.1.3, and Clause 5. It is assumed that the local corneal front surface and both contact lens surfaces are spherical or toroidal.This International Standard takes priority over ISO 15004-1, if differences exist.