Final answer:
Testing lateral eye movement assesses the abducens nerve (VI), which controls the lateral rectus muscle for eye abduction. The oculomotor and trochlear nerves are also integral to eye movement, coordinating with the abducens nerve to enable complex gaze stabilization and tracking.
Step-by-step explanation:
Assessing whether a patient can move their eyes laterally involves testing the functioning of the abducens nerve (VI). This nerve innervates the lateral rectus muscle, which is responsible for abducting the eye, or moving it away from the midline of the body. The ocularmotor and trochlear nerves (III and IV, respectively) also play decisive roles in controlling the extraocular muscles, facilitating complex eye movements, such as tracking a visual target like a pen tip through various positions. Poor coordination between these muscles and nerve signals can result in conditions like internuclear ophthalmoplegia, leading to issues such as diplopia, or double vision.