Structured Clinical Examinations are made objective by establishing performance criteria for required clinical behaviours, and using trained assessors to answer specified questions relating to the required behaviours.

Candidates are asked to examine a Subject (patient) and complete a corresponding Candidate Clinical Record Form for each of the four Clinical Examination components.

In keeping with this objective approach, CEO asks many binary value (“yes” or “no” answers) questions of trained Assessors in determining candidates' performance for the skills components.

Some questions posed to the assessors relate to the performance of common “milestones” involved in a particular technique. For example, the assessor may be asked if the candidate controlled accommodation during retinoscopy by “fogging” the opposite eye with plus-powered lenses. However, the majority of the questions posed to the Assessor relate to the accuracy of the results or findings obtained by the candidate. For example, the Assessor may be asked if the candidate obtained a specific far-point phoria result using the Risley rotary prisms of the phoropter. For these questions, results are deemed correct if they fall within a specified range. Minus Cylinder is required when reporting refractions or lens powers throughout the CSAO unless otherwise indicated.

Candidates interact verbally and otherwise with subjects throughout the skills components. These interactions are observed by the Assessors, who must answer specific questions about candidates interpersonal skills as demonstrated within each component.

One question is posed to the Assessor that asks whether the candidate's interpersonal skills, performance, accuracy and record keeping combine to make an effective whole, suitable for independent practice. This question item (overall impression) contributes to the candidate’s overall score in the component by simple addition