Spoilers: Deus Ex Machina
Summery: Can you smell it?
Sawyer didnt tell the Doc that the glasses only helped for the first two days (sharp inhaled breath as he fell against the tree and held on while he went blind).
After that, he could smell the burning (like the bodies from the crash. He would never eat bacon again if he could). And it got stronger with every throb of the migraine that left him shaking and sweating in the shade.
Doc had said that (the smell, the fire) could be the sign of a tumor, but Sawyer knew better.
Sawyer watched the kid (Walt, the dad called him) play with the dog (unnatural, shouldn't have survived the crash), and spat out the ashes from his mouth.
Sawyer knew where the fire would come from (innocent eyes burned the raft and smiled). And he knew what he would do (hands striking out against the water as he held the boy under).
Sawyer inhaled the scent of burning flesh, and smiled.