It might be a bit exaggerated, but I had an ex that had eyes like this, so it's not like it doesn't exist. But as far as Daz goes, the only "true" fix would be to take the base map, drop it into Photoshop, match the white/sclera as best as possible and paint away the red out in. Then drop the new versions back into the asset folder and slot it into the Base Color and Translucency Color sections.
That said, just find a model that has eyes you like and use them instead. Most likely going to fix both and far quicker than doing it manually. P3D usually makes some pretty good eyes just as a quick option, as do most of the Daz originals.