This study finds no correlation between night-lights and nearsightedness among infants. That's evidence that night-lights might not cause nearsightedness at all. But the doctor never claimed they do. The doctor's conclusion is conditional: if night-lights cause nearsightedness, the effect disappears with age. Providing evidence against the "if" doesn't weaken the conditional claim. It's like saying "if it rains, the streets will be wet" and someone responds, "but it's not going to rain." That doesn't make the reasoning about wet streets any weaker.

This rules out a specific alternative explanation for Study 1's results: that already-nearsighted children might be more likely to sleep with night-lights (reverse causation). That's interesting, but it doesn't challenge the doctor's claim about the effect disappearing with age. It's not giving us any reason to question the idea that the effect of nightlights on nearsightedness disappears with age.

These children didn't sleep with night-lights as infants. Since the doctor's argument is specifically about whether infant exposure to night-lights has effects that disappear later, a study of children who weren't exposed as infants doesn't test the right thing. It's like trying to determine whether a childhood vaccine wears off by studying people who never got the vaccine.

"Several" children being nearsighted doesn't establish a correlation between night-lights and nearsightedness. In any group of 100 children, several might be nearsighted regardless of whether they slept with night-lights. What would matter is whether the rate of nearsightedness is higher among those who slept with night-lights than among those who didn't. (E) doesn't tell us anything about that comparison. For all we know, 5 out of 50 night-light users and 5 out of 50 non-users were nearsighted, which would show no correlation at all.