Originally Posted by Echos
I'm familiar with the negative text-indent value making it so that the words don't appear on the page, but I can't seem to find anything about using it with an anchor on google. (Perhaps I just don't know what to search for)
There's really nothing unique about using negative text-indent with an anchor as compared to using it with any other type of text.
It's worth having more useful text within the anchor elements of your menu, not least because it gives users something to see and click on if they are viewing without CSS. It also helps bestow a sense of value and purpose to the link in the eyes of the search engines.
It also ensures that the link is usable
It's generally worthwhile to view a page without CSS to see if it remains usable. You should try to consider how the page might be presented to users with screen-readers or text-browsers. Without actual content within your anchor tags, a screen reader will either read out the url or may even ignore the link completely. Similarly, without content within the anchor tags, the link is likely to prove problematic for those using text browsers.
Tbh, I'm not sure how Google handles links with no content. It's possible that it doesn't follow them at all. It's possible that it may mistake them for internal fragment identifier links, rather than site navigation links, though, again, I'm not sure how it handles those either.
The use of a negative text-indent is simply to push the text of the links out of view. Without the text-indent, the text of the links will sit over your menu images and that's not going to look too good.