1. someone who can offer a new or different perspective to something
offer/bring a fresh pair of eyes to something
This expression refers to somebody who can examine or offer a critique of something, often a plan, text, or document, in an unbiased and clear way, usually as a result of not being involved in the creation process. If, for example, you have spent days writing a report, you might be so bogged down in the research and detail that you miss something important that somebody distant from the process could pick up on immediately. A 'fresh pair of eyes' is therefore very useful for spotting mistakes and offering new perspectives, which is why the term is so common in a professional context.