18 month old child presents with both eyes adducted. What is the first thing for diagnosis?

Given the age of the child in question, any test has to be performed under anesthesia(EUA), since the child will not cooperate for any examination. During EUA: Refractive error examination is done to rule out hypermetropia as a cause of B/L adduction. Force duction test is used for diagnosis of Restrictive strabismus (eg Duane's retraction syndrome).