How keen is a snakes eyesight?

And do different types of snakes have better or worse eyesight? A week or two ago our Sandboa got moved to a bigger home and he's now in front of a window. Ever since we moved him he has been out a lot more! He used to stay buried all the time...and he still does some of the time, but on a lot of days he is out more than he is in the sand. I had the thought today that maybe he's looking out the window?? He's also started hanging out at the front of the tank more...observing our activity I guess. Or is that a crazy thought? We handle him several times a day and he's super docile and friendly.

https://fbcdn-sphotos-h-a.akamaihd.n...69715893_n.jpg

and here is just a bonus pic of him trying to escape earlier today :D

https://fbcdn-sphotos-h-a.akamaihd.n...61523391_n.jpg