Argus at home, but a mole abroad.

The proverb contrasts sharp awareness in familiar surroundings with poor perception beyond them. Its exaggerated images make the difference pointed rather than merely descriptive.

It can characterize someone who notices every detail close to home yet overlooks things outside that setting. The failing is not necessarily eyesight, but a narrow range of attention or judgment.

Use it when someone's attentiveness changes markedly with their surroundings: they are quick to spot problems in a familiar setting but miss comparable things elsewhere. The contrast gives the remark a critical edge.