There isn't much else he can do, no point in fighting being turned back to face Lambert, though he does wave the tapping fingers away with his other hand. Childermass can easily guess what he's asking, but he isn't so inclined to try and show what the problem is. It would mean removing the arm from over his eyes and that is the problem.

"It's the light," he tries to explain instead, hoping to avoid at least a little suffering in case the witcher insists. "It feels like it's burning my eyes. Even with my arm over them, even with them closed..." It still stings, but that much is tolerable. For now. "I think it's getting worse."

On the bright side, he hardly sounds panicked over it. With what else is happening around the carnival, surely it's something to do with the mushi infestations. That means there's a cure, right? Assuming that hasn't vanished along with Ginko's repellant.