Bhagavad Gita, Chapter 11, Verse 8

But you cannot see Me with these eyes of yours; I give you supersensuous sight; behold My Yoga Power Supreme.

Ordinary eyesight is described here as genuinely insufficient, so something new has to be given first.

Krishna doesn't ask Arjun to strain harder or look closer, he grants an entirely different kind of sight. Real vision like this is shown as a gift, not an achievement.