Like I said earlier I got bilateral grommets 2 years ago. It will come up in your medical renewal because your doc will be looking inside your ears, so there is no beating around the bush there.
I went into my first renewal prepped with a letter from my ENT. We put it in with the paperwork, and I received my class 1 a few weeks later, no drama's from casa.
My grommets are still in place and my class 1 just came in my email today.
Have a letter from your ENT ready. There shouldn't be any issues though.