Trochlear

... innervates the face). 3) the optic canal and superior orbital fissure. the cranial nerves that move the eye muscles (abducent, occulomotor and trochlear nerves), the nerve that supplies the eye (optic nerve) and the blood vessels to the eye (opthalmic artery - branch of internal carotid artery) ...

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What does the trochlear nerve have to do with it? They only go to an eye muscle. I thought the iris is the responsability of nerve 3

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I think it's a matter of oculomotoric and trochlear cranial nerve and blindness is a problem with an optic cranial nerve...

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