Brutal Youth - S4-E5
Trivia: Jack Larson, who played Jimmy Olsen in "The Adventures of Superman" in the 50s, portrays Jimmy Olsen as an old man.
Trivia: Had the show carried on for a fifth season, it would have been revealed that the baby that was given to Lois and Clark was actually Kryptonian royalty and was given to them to protect the baby from assassins.
Trivia: Dean Cain's mom Sharon Thomas appears in three episodes of the show. "The Green, Green Glow of Home" as Maisie, "Season's Greedings" as the pretentious lady and in "Just Say Noah" as the nun who thanks Superman.
Answer: I don't recall if it was ever mentioned in an episode, but it's possible that the frames and/or lenses of his glasses are lined with lead, the one compound his X-ray vision can't penetrate. Speculative, of course, but it likely would have been done at a point in his youth when he wasn't in complete control of his powers.
Cubs Fan ★
I think the other answer has good speculation. I would add it could also just be an "acting gesture" that Dean Cain utilizes as part of his Superman character and not because there's any practical reason. That way, the audience immediately recognizes what he is doing.
raywest ★