can optic disc atrophy be reversible?

Answer 1

No.
That is my firm understanding from years in optometry, and I did a quick cross-check on-line too.

But.
Vison loss may be reversible, at least in part.
In a benign brain tumour.or with a multiple sclerosis episode involving the optic nerve (for examples), the vision may be severely reduced and signs of optic atrophy be present.
But the poor vision may not be just down to the permanent loss of fibres, and if the tumour is treated or the MS attack subsides, the vision may recover quite considerably though strictly the optic atrophy will not.