mrcem2-1420

mrcem2-1420

A 12-year-old boy comes in with complaints of double vision. He is holding his head tilted to the left-hand side. During the examination of his eye movements, it is observed that both eyes can look normally to the right, but on looking to the left, his left eye cannot turn outwards past the midline. The right eye is unaffected when looking to the left.
Which muscle is the MOST likely to be involved in this case?