Okay. This is a topic on one of the more subtler aspects of Sailor Moon. 

In the anime, when your heart crystal/dream mirror/star seed is extracted and/or taken, you lose the shine in your eyes. 

--->

The same thing happens too, when Sailor Moon pulls our her heart crystal in the S finale to achieve Super form. 

Essentially, the idea is, these objects (heart crystal/dream mirror/star seed) are pieces of your soul. With them extracted/taken, you essentially have lost your light/soul. 

So, what happened during the Stars finale? Uranus and Neptune, fighting their way, allowed Galaxia to take their star seeds and make them her minions. So, during this time, as you saw with the images provided with Neptune, their eyes lacked their shine. But then, you get: 

 

 

Keep in mind, when this happens to them, when the shine returns, they still do not have their star seeds. They are still wearing the bracelets Galaxia provided to them. 

How and why do you think, then, the shine was able to return to their eyes?

I think the bracelets provided a substitute. Because they can't live either without their star seeds, so they needed those bracelets for their life/returning some semblance of a soul/whatever (because when Galaxia took them back, they die again).

I believe Sailor Uranus and Neptune have such strong souls and a will to protect their princess that not even losing their star seeds can keep them away from their mission.
I also agree that Galaxia's bracelets served as a substitute.

Interesting. I've always thought that Galaxia's bracelets acted as a kind of artificial Star Seed, because they give the Animates the power to become Sailors. Only Star Seed-carriers can become Sailors, so the bracelets have to have some kind of power that mimics Star Seeds.