A creature, including a ghost, can see only a limited distance on the ethereal plane, due to the nature of the plane itself.
When a ghost is manifested, they are still on the ethereal plane, but are under the effects of the manifest ability. This would seem to imply that the vision is limited, however the Prime Material does not have the same visual qualities as the ethereal plane, which might imply that it is not limited.
(If not, that might explain why ghosts manifest....)
How far can a manifested ghost see into the Prime Material?