In the Bible, Eli grew gradually more blind, from partial sight up to the stage of 'his eyes were set so he could not see'. I'm not sure that would happen over the brief duration of the film, but maybe he wasn't fully blind in the film, but had learnt brail in 'the world before' so as to better be able to read.
I agree all the things above could prove he had bad eyesight or possibly even be blind, but there are parts in the film that make me think he could see at least slightly, like when the motorcycle gang attacked the two travellers, granted he could hear them, but he looked around the rubble to better see, and then pinpointed the gangleader in the bar in town.