Hi Psacra
Horama while it can be translated "seen" It's main slant is always that of being a vision. In it's other uses in the bible it always pertains to a visions happening.
Acts 11:5
5 "I was in the city of Joppa praying ; and in a trance I saw a vision, an object coming down like a great sheet lowered by four corners from the sky ; and it came right down to me,
Acts 12:9
9 And he went out and continued to follow, and he did not know that what was being done by the angel was real, but thought he was seeing a vision.
Acts 16:9-10
9 A vision appeared to Paul in the night : a man of Macedonia was standing and appealing to him, and saying, "Come over to Macedonia and help us." 10 When he had seen the vision, immediately we sought to go into Macedonia, concluding that God had called us to preach the gospel to them.
It appears 12 times in the greek scriptures and translated "vision" 11 out 12 times. Reflecting this most bible translate this as "vision" in mathew. No one doubts Jesus is literally saying and meaning "vision" in this verse.