Posts like this are generally accepted by the community, especially when they make it clear that the commentator has a relationship with the company.
What is technically against the guidelines is complaining about the appropriateness of a comment. It is preferred that you downvote or flag inappropriate comments. See https://news.ycombinator.com/newsguidelines.html
It pretty clearly crossed the spam line for me: The parent specifically pointed out that doctors don't give you the PD to in order to force you to buy glasses from them, but suggests there are other ways to obtain it. Eric replies to talk about how much better their app is than any do-it-yourself PD measurement but does not disclose that their app also doesn't give you the measurements in order to force you to buy glasses from them. I did not find this helpful and it is clearly commercial, since the app has no utility other than to sell you their glasses.
Oh look, a guy trying to be helpful while making some money mentions his product on a fucking tech-news website run by a famous startup incubator and you idiots want to report it?
What is technically against the guidelines is complaining about the appropriateness of a comment. It is preferred that you downvote or flag inappropriate comments. See https://news.ycombinator.com/newsguidelines.html