The word orthoptics comes from the Greek ortho meaning straight, and optikas meaning vision, and Orthoptists are allied health professionals who specialize in the study of ocular motility and visual development. In conjunction with an ophthalmologist, the orthoptist examines and aids in the diagnosis of visual system dysfunctions involving vision, eye movement, eye alignment and binocularity. Orthoptics focuses on the non-surgical treatment of amblyopia and strabismus.

Orthoptists specialize in the non-surgical treatment of visual disorders such as amblyopia, strabismus and diplopia. The orthoptist is the front line in the assessment and diagnosis of these disorders, and works with the ophthalmologist in formulating and implementing treatment plans.

For example, amblyopia is the lack of visual development, or the loss of visual ability due to disuse of the eye. In order for vision to develop equally, each eye must be capable of forming a clear image of the viewed object. If one eye is turned off axis (strabismus), one eye has a higher refractive error than the other (anisometropia), or there is disease of one eye, then both of the eyes are not viewing the same object or are not receiving equal pictures. Discrepant input does not allow for binocular co-operation, and the brain shuts off the offending eye (suppression). This halts visual development in that eye and the vision stagnates, and in many cases, deteriorates.

It is the job of the orthoptist to aid in the examination of conditions that may lead to amblyopia, and to determine if amblyopia exists. Many patients are pre-verbal, so the orthoptist must understand visual system development and integrate this with the knowledge of developmental milestones in order to make a sound judgement. To accurately assess visual capabilities, they use a variety of tests designed to work within the brief window of a child's attention. Amblyopia that is amenable to treatment (i.e. not caused by disease) may require treatment with glasses, occlusion (patching), and/or penalization therapy (drops). Armed with complete information about the child's visual system, including a fundus exam performed by an ophthalmologist and correct refraction (measurement for glasses), the orthoptist is the front line person in monitoring and reinforcing the treatment plan, and in offering support and guidance for parents.

The role of the orthoptist is quite different in the diagnosis and management of diplopia (double vision). Frequently, orthoptists are called upon to assess the visual function of adult patients for whom binocular vision has been disrupted. Diplopia can manifest from a variety of causes such as ocular disease, systemic disease, vascular disease, trauma, or refractive errors. The orthoptic examination determines how the binocular visual system has been affected, often lending to diagnosis of underlying disease. The orthoptist then takes steps to manage the visual comfort of the patient. Double vision can often be treated with prism therapy, which relies strongly on the orthoptist's knowledge of visual principles and ability to integrate these therapeutically.

The orthoptist is involved in diagnosis and treatment of many other disorders. They play an active role in the care of many ocular conditions in conjunction with the ophthalmologist.