If someone were to peer out of the window now, even Mrs Dursley (whose eyes shone like beads) probably wouldn't be able to see what was happening at all in this darkness.
Clearly ビーズのように光る目 was beady-eyed in the original English. As a native English speaker when someone says beady-eyed I don't think of this literal meaning but something more like this.
Is ビーズのように光る目 a natural phrase in Japanese or is it just a poor, literal translation.
If it isn't natural is there a better translation?