As far as the eye could see, the fields were pure white.
Literal
Eye [to-に] visible [limit-限り] fields [topic-は] pure-white was.
目に見える限り ('as far as visible') parallels 目の届く限り from earlier. 真っ白 ('pure white') uses the intensifying prefix 真っ~ (まっ~) on 白い. Evokes a snowy landscape.