Okay, the user sent "pop-eye". First, I need to check if this is already in Vietnamese. "Pop-eye" in Vietnamese is "mắt hóp", which refers to a sunken or recessed eye. Since the user's instruction says if the content is already in Vietnamese, output it unchanged. But wait, "pop-eye" is an English term. However, in Vietnamese, it's translated as "mắt hóp". So the user might be asking for a translation. But according to the rules, if the content is already in Vietnamese, leave it as is. But "pop-eye" isn't Vietnamese. So I should translate it to "mắt hóp". But I need to confirm if "pop-eye" is a known term in Vietnamese. Maybe the user is referring to a specific term or a brand. Alternatively, maybe they want the literal translation. The correct translation would be "mắt hóp". So the answer is "mắt hóp".