A.T. Robertson Commentary Mark 9:47

"And if thine eye cause thee to stumble, cast it out: it is good for thee to enter into the kingdom of God with one eye, rather than having two eyes to be cast into hell;" — Mark 9:47 (ASV)

With one eye (μονοφθαλμον). Literally one-eyed. See also Mt 18:9. Vernacular Koine and condemned by the Atticists. See Mt 18:8f. Mark has here "kingdom of God" where Mt 18:9 has "life."