Guess the hat colors - Riddle 7

My brother just created this puzzle for me for Halloween, at first I thought it looked simple, but then it turned out to be very challenging (at least for me!) I’ll add it to my collection/app soon. I hope you like it:

CHALLENGE: Guess the hats of the prisoners.

SPECIAL RULE: One of them is short-sighted, which means he can only see one hat in front of him. He is aware he is short-sighted, but nobody else knows who this person is. Everyone does know there is one short-sighted amongst them.

DESCRIPTION:
Each one can see the hats that are in front of them, and not their own. This means:

• A sees B,C and D; B sees C and D; C sees A and B; D sees A, B and C
• This last sentence is not true for the short-sighted one, which can only see the first one in front of him

They give tips one by one, pay attention to the order in which they speak:

1- A is the first one to talk. He sees more green hats than black ones. (This would mean he sees 2 green hats and 1 black hat, or only one green hat if A were the short-sighted one, which you will have to figure out)

2- Then D talks: he sees at least 1 black hat.

3- C speaks third and says that, from what he can see and what he has heard, B doesn’t know the hat he is wearing

4- Lastly, B says that only after listening to C (and not before), he can then figure out which hat he is wearing.

There are 2 green hats and 2 black hats, and all of them know this.

They know who talks, where they are sitting, and what direction they’re facing.

Good luck!