As far as the eye could see, there was nothing but wheat fields.

Literal

Eye [poss-の] reach [limit-限り], wheat-field outside [topic-は] anything not-visible-was.

麦畑以外は何も見えなかった ('nothing was visible except wheat fields') uses ~以外は…ない for 'nothing other than.' 見える is the potential/spontaneous form — 'be visible.' A sweeping rural landscape.