Preoperative diplopia testing in adults is extremely important in the determination of the type of strabismus and what medical or surgical management should be done. It helps in deciding if the patient should have surgery, what surgery should be done, and when to do it. The evaluation of postoperative diplopia also helps in determining the course of action-e.g., whether to wait and reassure, manage medically with prisms, or reoperate. Orthoptists, as part of the strabismus ophthalmology team, are uniquely skilled in all aspects of the diplopia exam and can help the surgeon make management decisions.