When it comes to visual perception, the terms can often be used interchangeably.
He has perfect vision. He has perfect eye sight.
His vision is 20/20. His eye sight is 20/20.
And there are many cases where one is more appropriate.
His vision of the field of play is spectacular. I had a vision of heaven. He blocked our vision (view) of the city.
She was a sight to behold. Sighted persons have no idea what it means to be blind. His response was short-sighted.
Acredito que traduzir como "A visao" nao é errado, até pq "Sight" significa o ato de enxergar e é traduzida como : Vista, visão etc
Ex: My sight grew dim ( Minha visão cresceu fraca).
Love at the first sight (Amor a primeira vista).
The sight of the stars makes me dream ( A visão das estrelas me faz sonhar).
Mais informações útil sobre as diferenças entre site e sight.