Can someone remind me why etienne and Richard the only ones with sparkly eyes ? Aren't the...

i think it only works with blue eyes

In the ABO universe, there's the obvious 3 secondary genders: Alpha, Beta and Omega. Betas are normal ppl, Alphas (M/F) can get the Omegas (M/F) pregnant. With Alphas and Omegas, there's recessive and dominant traits. Recessives are basic A's and O's. The reason they have sparkling eyes is because they are both dominant secondary genders. That is the only difference between recessive and dominant A's and O's

OH, forgot to put this. Etienne is a dominant Omega, which is why his mother is soooooo persistent about the medicine to hide it because it gets rid of the sparkling eyes, so that is why everyone thinks he's a beta

I don't think they're asking about that, i think they are asking about why rishar and etienne have sparkle eyes but the others dominants don't have sparkle eyes like they

Yes that's what's confusing me I know about abo stuff but why are they the only dominant ones with sparkly eyes

in my opinion i think it works with blue eyes since scientifically blue eyes are the lack of pigmentation in the eyes (i think?), since there's not so much pigmentation it's easier to see the sparkles (it's just my theory don't take it serious)

Has the story mentioned any other dominate AO's other than Rishar and Etienne?

Yes, besides the empress and antoine we can see some not important characters that are dominants, they just appears in one or two panels on the first chapters