What is it when we work on something too much to see any new errors? [duplicate]

Whether I write a long paper or presentation, or am reviewing one, after looking it it many times, it seems impossible to notice any additional issues. For example, I am helping a client prepare a document for external audit. I am one of the internal auditors asking for information to put in the document and reviewing to ensure that it meets the needs of the external audit. After many working sessions and revisions, I can no longer see any issues.

My friends and co-workers say the same thing. That's one reason why we always have a 2nd (and 3rd) person review everything after it is "done". Every new reviewer finds something new.

What is it called when we can't stop "reading between the lines", or whatever it is that keeps us from seeing more?

Not really the answer you are looking for, but the 2nd/3rd set of eyes is often referred to as a fresh set of eyes.