Which eye care professional specializes in measurement of eye movement and the extraocular muscles?

The correct answer focuses on the role of an orthoptist in assessing and treating disorders related to eye movement and the coordination of the extraocular muscles. Orthoptists are specifically trained to evaluate and manage conditions such as strabismus (crossed eyes) and other eye movement disorders. Their expertise includes administering tests that measure eye alignment, fixation, and the function of the extraocular muscles, which are crucial for proper binocular vision.

In contrast, an ophthalmologist is a medical doctor who specializes in eye and vision care, including surgery but is not exclusively focused on measuring eye movement. An optometrist provides primary vision care and performs eye exams but does not specialize in the detailed assessment of eye movement and muscle function as orthoptists do. An optician, on the other hand, primarily focuses on the fitting and dispensing of eyewear rather than the medical evaluation of eye movement. Thus, the specialization of the orthoptist in eye movement measurement distinctly supports the answer.