Guy in my program did something similar. Finished his IM residency... licensed.. boards... then did a one year pre-residency fellowship at the local VA (which the ophth residents rotated through.) The next year, he matched in ophthalmology. Good thing is he could moonlight due to being licensed/board certified. Bad thing is he was sort of worn out at the end... didn't want to even try for a fellowship.
Honestly, I think doing two years IM... then neurology... then neuro-ophthalmology fellowship makes you look like you have no idea what you really want to do. I'd complete IM....and then decide where to go.