This International Standard, together with ISO 15004-1, specifies minimum requirements and test methods for trial frames for holding trial case lenses, complying with ISO 9801, in front of a subject's eyes in order to assess visual acuity and facilitate optical correction of vision. This International Standard is applicable to lens holders mounted on headbands, bracket-mounted frames and frames mounted in the manner of spectacles with supports on the ears and the bridge of the nose. It is applicable to all types of trial frame, including half-eye and rotating lens holders. This International Standard is not applicable to refractor heads (see ISO 10341). This International Standard takes precedence over ISO 15004-1, if differences exist.