20yrs after a surgery tumor in pituitary, that touch x optic nerve create a eye field problem,i have a deterioration in field, why? no tumor exist

Depends: If you haven't you need re-imaging for recurrence even 20 years later. If there is no recurrence it is likely unrelated and the causes are many including both neurological and ophthalmologic which require exams for cause

Clarify this: Get an updated MRI of brain. If not explained, you could have a primary eye issue, such as glaucoma, or macular degeneration, so, an ophthalmologist should be sought.